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java web知识点总结

一 JAXP - DOM 1.XML解析 (1) XML解析方式

XML文档一般用来配置文件 , 其有两种解析方式 , 分别是 DOM 解析和 SAX 解析 , DOM是W3C组织推荐的标准(由于内存问题 , 没有被采用) , SAX是事实上的使用标准 .

(2)XML解析器

Crimson(Sun) , Xerces(IBM) , Aelfred2(dom4j)

(3)XML解析开发包

Jaxp(Sun) , Jdom , dom4j , pull(android 的sdk 自带)

2.JAXP介绍

Jaxp是Sun公司提供的一套XML解析API ;

Jaxp很好的支持 DOM 和 SAX 解析 ;

Jaxp开发包是J2SE的一部分 , 包括以下包或子包 , javax.xml , org.w3c.dom , org.xml.sax

在Jaxp包中定义了几个工厂类 , 程序员调用这几个工厂类 , 可以得到对xml文档进行解析的DOM 或 SAX 解析对象 .

3.相应的API解析

二 JAXP – SAX解析 XML

三 DOM4J解析 XML 1.dom4j介绍

Dom4j 是简单灵活开放的源代码库 , 其是由早起的JDOM开发团队分离出来的 , 与JDOM不同的是 , dom4j使用接口和抽象类 , 虽然API较为复杂 , 但是其提供了比JDOM更好的灵活性 .

Dom4j是非常优秀的java xml api , 具有性能优异 , 功能强大 , 极易使用的特点 .

采用dom4j的软件 , Hibernate , Sun的Jaxm .

使用dom4

2.怎样使用dom4j开发包

(1)解压dom4j压缩包 , 在根目录下有一个 dom4j-1.6.1.jar 这是dom4j的jar包 ;

(2)在MyEclipse中的工程的根目录下创建一个文件夹 , 命名为 lib , 将dom4j-1.6.1.jar 文件复制到 lib文件夹中 ;

(3)右键点击 dom4j-1.6.1.jar , 选择Build Path | Add to Build Path , 这样这个jar包就导入到了这个工程中 , 我们就可以使用dom4j中的类和方法了 ;

(4)在一些时候我们使用dom4j中的类和方法的时候 , 会报出类没有找到异常 , 我们还需要导入一些其他的包 , 这些包在dom4j文件下的 lib 文件夹下 , 根据报错信息 , 找到相应的jar包 , 复制到工程下的lib文件夹下 , 然后设置 Build Path .

3.API介绍 (1)SAXReader [read()]_org.dom4j.SAXReader , Document [getXMLEncoding()]_org. dom4j.Document

这是dom4j提供的解析器 , 该解析器提供了一个方法 ,

read() (从一个已知的文件中读取一个Document对象) , 传入一个文件 , 返回Document对象 , 可以用来获取Document对象 .

这里注意了 , Document是一个接口 , 没有构造函数 , 不能通过构造函数获取Document对象 , 只能通过其他方法获取 .

获取Document对象的方法 : 先获取SAXReader解析器 , 即创建一个SAXReader对象 ; 然后解析xml文档 , 就是调用read()方法 , 获取Document文档 .

其中解析器read()方法 , 传入的参数是一个文件对象 , 这里可以新建一个文件 , new File(“books.xml”) ;

为了验证是否成功获取Document对象 , 我们使用Document类下的getXMLEncoding()方法 , 该方法返回的是Document对象所对应的XML文档的编码码表 , 例如UTF-8 , GBK等 , 这个码表值是在XML的第一行的标注中的.

一般XML文档的第一行都是 , 这里的encoding就是 getXMLEncoding()方法获得的返回值 .

( 返回文档的码表值 , 这个码表值是XML文档的一部分 , 当编码未指明或者未知或者系统不支持这个码表的时候其返回值为null) .

*****************************************************************************

一个获取document对象的方法:

Import java.io.File;

Import org.dom4j.Document;

Import org.dom4j.io.SAXReader;

Public static Document getDocument(){

//获取解析器

SAXReader reader = new SAXReader();

//解析XML文档

Document document = reader.read(new File (“books.xml”));

//验证是否成功获取Document对象

System.out.println(document.getXMLEncoding());

//返回Document对象

return document;

}

***************************************************************************

注意上面的方法导入了三个包 :

当使用到Document的时候需要导入包 org.dom4j.Document;

当使用到SAXReader的时候需要导入包org.dom4j.io.SAXReader ;

当使用到File的时候 , 需要导入包 java.io.File;

(2)Document[getRootElement()]_org.dom4j.Document , Element[]_org.dom4j.Element

Document类下的getRootElement()方法 , 是返回根节点 .

(返回文档的根节点) , 返回值是Element对象 , 是个XML 文档的元素 .

Element类定义了一个XML文档的元素 , 使用Element需要提前导入包 org.dom4j.Element .

这里注意了 : Document 和 Element 都是接口 , 都没有构造函数 , 只能通过其他方法获得 .

******************************************************************************

遍历所有节点的方法 :

(粉色的字体为要导入包的类)

Import java.util.List;

Import org.dom4j.Document;

Import org.dom4j.Element;

Public static void getAllBooks() throws Exception{

//获取Document对象 , 其中的getDocument是调用的上面(1)中的方法

Document document = getDocument();

//获取根节点

Element rootElement = document.getRootElement();

//获得所有的书

List bookList = rootElement.Elements();

//遍历所有的书

For(int i = 0 ; I < bookList.size() ; i++){

//获得每一本书 , 注意从集合中获取元素 , 涉及到强转

Element book = (Element)bookList.get(i);

List childList = book.Elements();

//获取每一本书的子节点

For(int j = 0 ; j < childList.size() ; j++){

Element child = (Element)childList.get(j);

System.out.println(child.getName() + ”:” + child.getText());

}

****************************************************************************

代码解析 :

A.Element调用的getName()和getText()方法 .

getName()和getText()方法并不是Element类下定义的方法 , Element类是Node类的子类 , 这两个方法是从Node类中继承的 .

(返回这个结点的名字) ;

(返回这个结点的文本) ;

B.导入包的介绍:

当使用Document类的时候需要导入包 org.dom4j.Document ;

当使用Element类的时候需要导入包 org.dom4j.Element ;

当使用List类的时候需要导入包 java.util.List .

C.代码思想

从根节点之后 , 调用Element()方法 , 将结点的子节点放入一个集合中 .

然后遍历这个集合 , 将元素从集合中取出 , 注意从集合中取出元素 , 集合并不知道取出的是什么类型 , 取出的类型一律为Object , 这里我们需要将取出的元素强转为Element类型 .

然后在调用Element()方法 , 获取从集合中取出的Element类型的子节点 , 以此类推 .

最后是将元素的名称和文本输出 , 树有几层 , 有要嵌套几层循环 , 只在最内层的循环中输出元素名称和文本 .

根节点rootElement , 在XML文档中是标签 ;

获取根节点的子节点book , rootElement.element() , 获取的就是标签下的子标签 ;

获取book的子节点child , book.element() , 获取的就是标签下的子标签和<price>;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">获取<title>标签的标签名的方法 getName() , 获取<title> 标签文本的方法 getText .</span> </div> <span style="word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> (3)Element[attributeValue(qName)]_org.dom4j.Element , String[equalsIgnoreCase()]</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> AttributeValue(qName)是Element下的方法 , 其返回值是 , 返回名称为qName属性的属性值 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> equalsIgnoreCase()是String类下的方法 , 目的是判断两个String类死否相等 , 不区分大小写 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> *******************************************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 获取实体类集合的方法:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>Import java.util.List; </div> <div style="word-wrap:break-word"> Import java.util.ArrayList; </div> <div style="word-wrap:break-word"> Import java.io.File; </div> <div style="word-wrap:break-word"> </div> <div style="word-wrap:break-word"> Import org.dom4j.Document; </div> <div style="word-wrap:break-word"> Import org.dom4j.io.SAXReader; </div> <div style="word-wrap:break-word"> Import org.dom4j.Element; </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Public static List getBooks() throws Exception{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获取document , 先获取解析器 , 再通过解析器获得document </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">SAXReader</span> reader = new SAXReader();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Document</span> document = reader.read(new <span style="word-wrap:break-word">File</span>(“books.xml”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获取根节点 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Element</span> rootElement = document.getRootElement();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获取根节点的子节点的集合 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">List</span> bookList = rootElement.elements();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//创建存取书的实体类集合 , 该实体类已在本包中定义 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> List returnBook = new <span style="word-wrap:break-word">ArrayList</span>();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//将xml文档中的信息存到Book实体类中 , 然后将Book实体类存入到returnBook集合中 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> For(int i = 0 ; i < bookList.size() ; i ++){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获得每一本书 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Element book = (Element)bookList.get(i);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//创建Book实体类 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Book bookBean = new Book();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//设置id </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> bookBean.setId(book.attributeValue(“id”));</span> </div> <div style="word-wrap:break-word"> //获取书的子标签集合 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> List childList = book.elements();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获取每一个标签 , 将标签的文本放到Book实体类中 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> For(int j = 0 ; j < childList.size() ; j ++){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Element child = (Element)childList;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> If(“title”.equalsIgnoreCase(child.getName())){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> bookBean.setTitle(child.getText()); </span>//设置titile字段 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}else if(“price”.equalsIgnoreCase(child.getName())){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> bookBean.setPrice(child.getText()); </span>//设置price字段 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">returnBook.add(bookBean);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Return returnBook;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">********************************************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">代码解析 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. Book类是在这个包中定义的一个存放xml文档信息的实体类 , 其有三个字段 , id , title 和 price , 以及有相应的get set方法 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">设置字段的时候直接使用其set方法即可 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">B. 该代码中Element类中所调用的getName()和getText()方法 , getName()方法是返回xml文档元素的标签名 , getText()方法是返回xml文档元素的标签内的文本 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">C. 导入包介绍</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用 <span style="word-wrap:break-word">List</span> 类的时候需要导入包 <span style="word-wrap:break-word">java.util.List </span>;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用 <span style="word-wrap:break-word">ArrayList</span> 类的时候需要导入包 <span style="word-wrap:break-word">java.util.ArrayList</span> ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用<span style="word-wrap:break-word"> File</span> 类的时候需要导入包<span style="word-wrap:break-word"> java.util.io.File</span> ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用 <span style="word-wrap:break-word">SAXReader </span>类的时候需要导入包 <span style="word-wrap:break-word">org.dom4j.io.SAXReader</span> ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用 <span style="word-wrap:break-word">Document</span> 类的时候需要导入包 <span style="word-wrap:break-word">org.dom4j.Document</span> ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当使用 <span style="word-wrap:break-word">Element</span> 类的时候需要导入包 <span style="word-wrap:break-word">org.dom4j.Element </span>;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> D. 代码思想</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">通过SAXReader解析器获取document , 然后通过document方法获取根节点<books> , 获取到根节点之后 , 就可以获得二级节点 book , 然后就可以获取book下的子标签 child的标签名和文本 , 将book的属性id 和 book的子标签的标签名和文本名设置到Book的实体类bookBean中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">这里涉及到了两层嵌套循环 , 第一层循环获取book标签 , 第二层循环获取book标签下的子标签 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">四</span><span style="font-family:Times New Roman; word-wrap:break-word"> JDK</span><span style="font-family:宋体; word-wrap:break-word">新特性</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">静态导入</span><span style="font-family:Arial; word-wrap:break-word"> Static Import</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">静态导入介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 静态导入就是导入某个类的静态属性或静态方法 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">语法</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">:</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. <span style="word-wrap:break-word">导入指定的单个静态属性</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">import static 包名.类名.静态属性 ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Import static java.lang.System.out ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. <span style="word-wrap:break-word">导入指定静态方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">import static 包名.类名.静态方法 ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Import static java.lang.Math.max ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 注意导入静态方法的时候 , 只写上方法名 , 括号/修饰符/参数列表/方法体等不带 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. <span style="word-wrap:break-word">导入指定类全部静态属性和方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">import static 包名.类名.* ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Import static java.lang.Math.* ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 注意: 加上了static , 后面有*的话导入的全是静态的属性和静态方法 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果没有加上static , 那么导入的就是所有的属性和方法 , 包括静态的和非静态的 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">代码示例</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">:</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ****************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> import java.lang.Math.PI ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> import java.lang.Math.max ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public static void main(String[] args){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //导入静态字段 , 属性</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> double a = Math.PI ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println(a) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println(PI) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //导入静态方法</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Int b = Math.max(1, 2) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println(b);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println(max(1,2));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">*******************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">代码思想 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果没有导入静态字段和方法 , 不能直接使用PI和max()方法 , 如果使用了就会报错 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">自动装箱</span><span style="font-family:Arial; word-wrap:break-word">,</span><span style="font-family:黑体; word-wrap:break-word">拆箱</span><span style="font-family:Arial; word-wrap:break-word"> AutoBoxing/Unboxing</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (1)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. </span><span style="font-family:黑体; word-wrap:break-word">泛型</span><span style="font-family:Arial; word-wrap:break-word"> Generics</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">泛型介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. Jdk5.0之前 , 对象保存到集合中就会失去其特性 , 取出时通常要程序员手工进行类的强制转化 , 这样就不可避免的引发一些程序上的安全性问题 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 泛型格式 : 类型<T></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. 泛型的基本术语</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 以ArrayList<E>为例 , 念作 ArrayList type of E ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ArrayList<E> , E称为类型参数变量 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ArrayList<Integer> , Integer成为实际类型参数 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">ArrayList<E> 整个称为泛型类型 ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ArrayList<Integer>成为参数化的类型ParameterizedType .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">泛型的作用</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Jdk5中的泛型 , 允许程序员在编写集合代码的时候 , 就限制集合的处理类型 , 从而将运行时可能发生的问题 , 转变为编译时的问题 , 从而提高程序的可读性和稳定性 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个作用在大型程序中尤为突出 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">类型擦出</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 泛型是提供给javac编译器使用的 , 它用于限定集合的输入类型 , 让编译器在源码级别上挡住向集合中插入非法数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 编译器编译完带有泛型的java源文件之后 , 生成的class文件不再带有泛型信息 , 这个过程称为类型擦出(type erasure) .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public void print(List<String> list){}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public void print(List<Integer> List){}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面两个方法不能同时存在 , 由于类型擦出效果 , 这两个方法在编译之后生成的class文件是没有区别的 , 这样两个函数就完全相同了 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(4)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">泛型的典型应用</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 4. </span><span style="font-family:黑体; word-wrap:break-word">增强</span><span style="font-family:Arial; word-wrap:break-word">for</span><span style="font-family:黑体; word-wrap:break-word">循环</span><span style="font-family:Arial; word-wrap:break-word"> (for - each) Enhanced for Loop</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (1)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (2)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (3)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 5. </span><span style="font-family:黑体; word-wrap:break-word">可变参数</span><span style="font-family:Arial; word-wrap:break-word"> Varargs</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 6. </span><span style="font-family:黑体; word-wrap:break-word">枚举</span><span style="font-family:Arial; word-wrap:break-word"> Typesafe Enums</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">五</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">反射</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">反射介绍</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 反射就是通过字节码文件 , 获得类中的构造函数 , 方法 , 字段 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 注意 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class下的api , 获得公共的构造函数 , 方法 : getConstructor() , getMethod() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 获得声明的构造函数 , 方法 : getDeclareConstructor() , getClareMethod() , 这里获得的构造函数或者方法不一定是公共的 , 私有的也可以获得 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">获得</span><span style="font-family:Arial; word-wrap:break-word">Class</span><span style="font-family:黑体; word-wrap:break-word">类</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">通过类名获得</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Class</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">对象</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">注意这个类名不带 .class 后缀</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Class clazz = Class.forName(“my.cn.itcast.reflect.ReflectTest”);</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">通过已知类获得</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Class</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">对象</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 直接将字节码文件赋给Class对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class clazz2 = ReflectTest.class ;</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">通过已知对象获得</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Class</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">对象</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Object object = new ArrayList();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class clazz3 = object.getClass();</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(4)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">实例化</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Clazz.newInstance() ; 是调用获得的Class对象默认的构造函数创建相应的实例 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. Constructor</span><span style="font-family:黑体; word-wrap:break-word">类</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得公共的构造函数</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Clazz是Class类对象 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Constructor con = clazz.getConstructor();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这样con就是返回的构造函数 , 如果想要调用这个构造函数创建实例 , 可以使用 con.newInstance()创建实例 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 使用clazz.newInstance()调用默认的构造函数创建实例 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得声明的构造函数</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">可获得私有构造函数</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">)</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Constructor con = clazz.getDeclaredConstructor(String.class , Integer.class) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在类中这个构造函数是私有的 , 我们如果使用con.newInstance()调用这个方法 , 就会吧报出异常 , 我们如果想要调用这个私有的构造方法创建实例 , 就要将该构造函数设置为可访问的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Con.setAccessible(true);</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 进行了以上设定之后 , 我们就可以使用con.newInstance()方法创建实例了 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> 4. Field</span><span style="font-family:宋体; word-wrap:break-word">类</span></span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得公共的字段</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class类中有可以获取Filed类对象的方法 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class clazz = Class.forName(“cn.itcast.reflect.ReflectData”); //获得Class类对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Object obj = clazz.newInstance(); //调用默认函数实例化</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //获得公共字段</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Field field = class.getField(“name”) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println(field.get(obj));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Field类下的get(Object object) 方法 , 将指定对象上该Field字段值返回 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得私有的字段</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Field field = clazz.getDeclaredField(“age”) ;</span> </div> <div style="word-wrap:break-word"> <span style="font-size:14px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Courier New; word-wrap:break-word"> </span>使用<span style="font-family:Courier New; word-wrap:break-word">Class</span>类下的<span style="font-family:Courier New; word-wrap:break-word">getDeclaredField()</span>方法可以获取私有的字段值<span style="font-family:Courier New; word-wrap:break-word"> , </span>传入的参数是字段值的名称<span style="font-family:Courier New; word-wrap:break-word"> .</span></span></span> </div> <div style="word-wrap:break-word"> <span style="font-size:14px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Courier New; word-wrap:break-word"> </span>注意<span style="font-family:Courier New; word-wrap:break-word"> , </span>私有的字段值不能被访问<span style="font-family:Courier New; word-wrap:break-word"> , </span>如果强行访问就会报出异常<span style="font-family:Courier New; word-wrap:break-word"> , </span>若想要正常访问<span style="font-family:Courier New; word-wrap:break-word"> , </span>需要将其设置为可访问<span style="font-family:Courier New; word-wrap:break-word"> .</span></span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Courier New; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> Field.setAccessible(true) ;</span></span></span> </div> <div style="word-wrap:break-word"> <span style="font-size:14px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Courier New; word-wrap:break-word"> </span>这个<span style="font-family:Courier New; word-wrap:break-word">Accessible</span>默认为<span style="font-family:Courier New; word-wrap:break-word">false , </span>我们设置其为<span style="font-family:Courier New; word-wrap:break-word">true , </span>之后就能访问相应的字段<span style="font-family:Courier New; word-wrap:break-word"> .</span></span></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 5.Method</span><span style="font-family:黑体; word-wrap:break-word">类</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得公共方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Class clazz = Class.forName(“cn.itcast.”) ; //根据名称获取Class对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Object obj = clazz.newInstance(); //调用默认的构造函数创建Class对象实例</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //getMethod()是Class类下的方法</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Method method = Clazz.getMethod(“print”) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 注意 , 这个方法传入的参数情况 , 必须传入的参数是方法名 , 后面还可以传入方法的参数类型类别 , 注意这个类型格式是类型名.class .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如 : 原来的方法是 public void print(int i , List list){} 如果想要获得这个方法就要使用下面的代码:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Method method = clazz.getMethod(“print” , int.class , List.class) , 后面的是一个可变参数 , 可变参数就是可以使任意个参数 , 参数个数和类型由方法的参数决定 , 如果原来的方法没有参数 , 在getmethod()方法中只传入方法名 , 如果原来的方法中有n个参数 , 那就在获取这个方法的时候 , 除了传入方法名之外 , 还要传入那n个变量类型 , 注意变量类型格式 , 类型名.class .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> method.invoke(obj);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> invoke()方法是Method下的方法 , Method对象调用这个方法 , 传入一个字段所在类的对象 , 和一个可变参数(就是方法自身的参数 , 格式仍然是参数类型名.class) , 相当于传入的对象调用这个方法 , 调用方法的同时传入后面的可变参数 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">获得私有方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Method method = clazz.getDeclaredMethod(“print” , int.class);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Method类下有一个getDeclaredMethod()方法 , 传入的参数与getMethod()方法传入的参数相同 , 一个方法名称字符串 , 一个可变参数 , 可变参数是方法参数类型 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个方法也能调用 method.invoke(obj , 1234) 执行 , 执行前必须将这个方法设置成可访问 , 否则就会报出异常 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> method.accessiableValue(true) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> method.invoke(obj , 1234);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这样就相当于执行了原来的私有方法 , 传入参数1234 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 6.</span><span style="font-family:黑体; word-wrap:break-word">反射总结</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (1)获得构造函数(Constructor) , 字段(Field)的方法都是在Class类中定义的 , 这几种方法都不是静态的 , 需要通过对象实例调用 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (2)获得公共构造函数和公共字段 : getConstructor() , getField()</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getConstructor()中传入类型.class 参数类型列表 , 例如 String.class , int.class 等 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getField() 中传入的是字符串 , 如果字段名(成员变量名)为 name , 那么就将 “name” 传入到方法中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (3)获得私有的构造函数和私有字段 : getDeclaredConstructor() , getDeclaredField() , 传入的参数与获得公共的构造函数和公共字段方法传入的参数相同 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 私有的构造函数和私有的字段不能直接被调用 , 如果想要调用私有的构造函数和私有字段 , 需要将相应的私有构造函数和私有字段设置为可访问的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在Constructor和Field下有setAccessible()方法 , 传入一个布尔值 , 默认的为false , 传入true , 就可以调用相应的私有构造函数和私有字段了 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">(4)注意使用Constructor类和Class类下的newInstance方法创建的实例 , 其类型为Object类型的 , 系统不知道其原来的类型是什么 , 如果要将实例赋值给原来的类型, 就需要强制转换类型 , 这里跟从集合中取出对象是一个道理的 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">六</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">单例</span></span></span> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"></span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"></span></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">单例描述</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">单例就是一个类在整个程序中只有一个实例 , 不能存在第二个该类的实例 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">单例模式的实现方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. 私有化构造方法 , 由于只能存在一个实例 , 那么就不能调用构造方法 , 使用户不能通过构造函数创建实例 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 获取方法:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 通过公共静态方法创建单一的实例 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 通过静态工厂方法获取实例 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">单例模式代码实例</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> *************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 饿汉模式:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Public class SingletonTest{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Private SingletonTest(){ //私有化构造函数</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Private static SingletonTest sing = null ; //声明一个私有的对象 , 并赋值null</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Static{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Sing = new SingletonTest() //在静态代码块中创建对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Public static SingletonTest getInstance(){ //公共静态方法返回这个单例对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Return sing;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">*************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 代码分析:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. 方法以及变量的修饰符分析</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">构造函数私有化是为了避免用户调用构造函数 , 创建出实例 , 由于只能创建一个实例 , 所以我们只能在类内部创建这个实例 , 不能在外部创建实例 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">声明一个私有的对象 , 这个对象不能被外部调用 , 这是为了专门提供给共有的方法来调用的 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">静态代码块在类第一次加载的时候执行 , 且只执行一次 , 一旦执行过了 , 下一次在加载类就不会执行这个静态太代码块了 , 这也是饿汉模式的原因 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">该类中只有一个公有的方法 , 这个方法提供给外部调用 , 用来获得唯一的一个实例 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 为什么叫饿汉模式</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 由于创建实例是放在静态代码块中执行的 , 仅执行一次 , 不管取出多少次 , 就仅将第一次创建的实例返回 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ********************************************************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 懒汉模式 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Public class SingletonTest2{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Private SingletonTest2(){ //私有化构造函数</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Private static SingletonTest2 sing = null; //声明实例对象私有静态</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Public static SingletonTest2 getInstance(){ //设置公共静态的方法 , 供用户调用唯一的实例对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> If(sing == null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Sing = new SingletonTest2();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Return sing ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">*********************************************************************************************</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 代码分析:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. 构造函数私有化 , 避免用户调用构造函数 , 创建多余的实例 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">B. 懒汉模式 : 不管之前有没有创建实例 , 都调用这个方法 , 如果没有创建就创建 , 如果创建了就直接返回 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">七</span><span style="font-family:Times New Roman; word-wrap:break-word"> Web</span><span style="font-family:宋体; word-wrap:break-word">入门</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. Web</span><span style="font-family:黑体; word-wrap:break-word">开发相关知识</span><span style="font-family:Arial; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)B/S</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">模式</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Web采用B/S模式 , 通过超文本传输协议(HTTP , Hypertext transport protocol)进行通信 , 是无状态通信 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B/S是 Browser / Server , 浏览器服务器架构 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C/S是 Client / Server , 客户端服务器架构 ;</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)Web</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">特点</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. 用超文本标记语言 ( HTML , Hypertext Markup Language ) 来表达信息 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 用统一资源定位 ( URL , Uniform Resource Locator ) 来对来自网络上的信息进行精确的定位 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. 用DNS来解析域名 , 用以方便记忆 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> D. 用网络应用层之间的协议HTTP来实现与Web服务器之间的通信 , 底层为 TCP/IP协议 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">静态资源与动态资源</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. Internet上供外界访问的Web资源分为静态资源和动态资源两种 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 静态Web资源开发技术是Html ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. 常用的动态Web开发技术有 JSP/Serverlet , ASP , PHP ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> D. 在Java中 , 动态Web开发技术统称为JavaWeb .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">开发企业级应用介绍</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">(1)ERP</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">(Enterprise Resource Planning) : 企业资源计划 , 针对物资资源管理(物流) , 人力资源管理(人流) , 财务资源管理(财流) , 信息资源管理(信息流) 集成一体化的企业管理软件 .</span> </div> <span style="word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">(2)CRM</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (Customer Relationship Management) : 客户关系管理 , 是指用计算机自动化分析销售 , 市场营销 , 客户服务以及应用支持等流程的软件系统 .</span> </div> <span style="word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">(3)BPM</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (Business Process Management) : 是一套达成企业各种业务环节整合的全面管理模式 .</span> </div> <span style="word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">(4)OA</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (Office Automation) : 办公自动化 , 是将现代化办公和计算机网络结合起来的一种新型的办公方式 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. Web</span><span style="font-family:黑体; word-wrap:break-word">系统通信方法</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 客户端发出请求 , 客户端请求包含用户要访问的资源路径和名称 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 服务器端接到请求 , 可以将页面 , 图片 , 媒体 , 等很多的资源内容发送给客户端 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果客户端请求没有得到正确处理 , 服务端会响应一个所悟状态码 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 4. URL</span><span style="font-family:黑体; word-wrap:break-word">格式</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>http://www.baidu.com:80/liyanhong/web/1.html </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">http://</span> 是协议 , 采用哪种协议进行本次网络访问 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">www.baidu.com</span> 是服务器 , 服务器的唯一域名 , 映射到一个IP地址 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">:80</span> 端口 , 访问服务在<span style="word-wrap:break-word">服务器端</span>绑定的端口号 , 如果没有指定端口 , 默认为80 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">/liyanhong/web/</span> 路径 , 由零个或多个 / 隔开的字符串 , 一般表示主机上一个目录或文件的地址 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">1.html</span> 资源名称 , 资源是本地计算机上的文件 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">5 </span><span style="font-family:黑体; word-wrap:break-word">常见服务器简介</span></span><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)WebLogic</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 是Oracle公司的产品 , 是目前应用最广泛的服务器 , 支持J2EE规范 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)WebSphere</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 是IBM公司的产品 , 支持J2EE规范 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)apache</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Tomcat , 支持全部Jsp与Servlet规范 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">八</span><span style="font-family:Times New Roman; word-wrap:break-word"> Tomcat</span><span style="font-family:宋体; word-wrap:break-word">安装与启动</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1.</span><span style="font-family:黑体; word-wrap:break-word">下载并安装</span><span style="font-family:Arial; word-wrap:break-word">Tomcat</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (1)下载Tomcat</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Tomcat官方站点</span> <span style="color:#000000; word-wrap:break-word"> : </span> <span style="color:#0000ff; word-wrap:break-word">http://archive.apache.org/dist/tomcat/</span> <span style="color:#000000; word-wrap:break-word"> ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在上面的网站获取Tomcat , tar.gz文件是Linux系统下的安装版本 , exe文件是Windows下的安装版本 , zip文件是Windows下的压缩版本 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (2)安装Tomcat</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这里我们下载的是apache-tomcat-6.0.35.zip , 解压缩到E盘的DevelopPakage , 一些开发包文件都放在这里 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2.</span><span style="font-family:黑体; word-wrap:break-word">启动</span><span style="font-family:Arial; word-wrap:break-word">Tomcat</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 双击Tomcat/bin/startup.bat , 就可以启动Tomcat .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 打开浏览器 , 输入</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:8080/</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#000000; word-wrap:break-word">能条转入Tomcat服务器界面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">九</span><span style="font-family:Times New Roman; word-wrap:break-word"> Tomcat</span><span style="font-family:宋体; word-wrap:break-word">配置</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1.Tomcat</span><span style="font-family:黑体; word-wrap:break-word">常见问题</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">启动闪了一下并消失</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果启动的时候 , 仅仅是闪了一下 , DOS界面就消失了 , 此时Tomcat并没有启动成功 , 这是因为我们没有配置 JAVA_HOME 环境变量 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这是我们右键点击我的电脑|属性|高级|环境变量|新建Administrator环境变量| 在弹出的对话框中的变量名选项输入 JAVA_HOME , 在变量值选项输入jdk的根目录路径 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">地址占用异常</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果报出了地址被占用异常 , 我们需要查看到底是那个程序占用了Tomcat需要的8080端口 , 并终止这个程序 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 查找端口的方法 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. cmd新建一个DOS命令窗口 , 输入 netstat –abo (注意中间是一个空格) , 会将端口使用情况列出 , 如果端口过多 , 一部分信息就不会显示出来 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. 使用Fport.exe工具查看 , 这个工具不能直接双击运行 , 需要在DOS命令窗口运行 , 将其方法 E:/DevelopPakage 文件夹下 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Cmd一个DOS命令窗口 , 将操作目录变为 E:/DevelopePakage , 然后输入 Fport.exe , 执行这个文件 , 与javac类似 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. 使用360安全卫士中的网络连接查看器 , 可以在这里查看端口使用情况 , 并且这个功能更强大 , 能终止被使用的端口 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 微软的SQLServerServersServer.exe SQLServer服务器报表服务宿主程序占用了次8080端口 , 我们将Tomcat的端口改为18080 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">修改端口方法</span> :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 打开根目录下的conf文件 , 打开server.xml , 其中只有一处8080 , 将其改为18080 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <Connector port="18080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connector 标签下的port 是端口 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Protocol 是协议 , 使用的是http协议 , 版本是 1.1的 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">在</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">MyEclipse</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">中配置</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Tomcat</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 打开MyEclipse , 选择 Window|Preference|MyEclipse|Servers|Tomcat|Tomcat 6.x</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 因为我这里用的是apache-tomcat-6.0.35.zip , 因此选的也是 Tomcat 6.x ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Tomcat Server 选择 Enable , 然后在第一个 Tomcat Home directory 浏览选择Tomcat的根目录 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这样就成功在MyEclipse中成功配置了Tomcat .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 此时的Tomcat在Server中 , Server就是我们平时打印东西的地方Console旁边 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们可以选择Server中的Tomcat服务器 , 右键选择Run , Tomcat就成功启动了起来 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果在Windows中启动的话 , 如果启动失败 , 这个DOS命令窗口就会消失 , 就不能在DOS命令窗口查看具体出了什么错误 , 在MyEclipse中显然可以查看启动过程供出现的错误 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(4)Tomcat</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">服务器和</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">版本之间的关系</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Tomcat</span> 7.0.x <span style="word-wrap:break-word">Servlet</span> 3.0 <span style="word-wrap:break-word">Jsp</span> 2.2 <span style="word-wrap:break-word">Java EE</span> 6.0</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Tomcat</span> 6.0.x <span style="word-wrap:break-word">Servlet</span> 2.5 <span style="word-wrap:break-word">Jsp</span> 2.1 <span style="word-wrap:break-word">Java EE</span> 5.0</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Tomcat</span> 5.5.x <span style="word-wrap:break-word">Servlet</span> 2.4 <span style="word-wrap:break-word">Jsp</span> 2.0 <span style="word-wrap:break-word">Java EE</span> 1.4</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Tomcat</span> 4.1.x <span style="word-wrap:break-word">Servlet</span> 2.3 <span style="word-wrap:break-word">Jsp</span> 1.2 <span style="word-wrap:break-word">Java EE</span> 1.3</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Tomcat</span> 3.3.x <span style="word-wrap:break-word">Servlet</span> 2.2 <span style="word-wrap:break-word">Jsp</span> 1.1 <span style="word-wrap:break-word">Java EE</span> 1.1</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 1.3的xml文件是dtd的 , 1.4之后的xml文件是schema的 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(5)MyEclipse</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">比</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">jdk</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">先安装</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果使用的MyEclipse安装了以后 , 将之前的jdk卸载了 , 重新安装的 , 这是在启动Tomcat就会启动不成功 , 这时我们需要在下面进行配置 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> MyEclipse | Window | Preferences | MyEclipse | Servers | Tomcat | Tomcat 6.x | JDK 下进行设置 , 设置完毕之后就能正常启动Tomcat了 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. Tomcat</span><span style="font-family:黑体; word-wrap:break-word">目录结构和权限设置</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(1)Tomcat</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">目录层次结构</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. bin目录中存放启动和关闭Tomcat的脚本程序 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. conf 存放Tomcat中各种配置文件</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. lib 存放的是Tomcat程序和所有的Web应用程序所访问的jar文件 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> tomcat-i18n-es.jar 是与国际化有关的文件 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> servlet-api.jar , jsp-api.jar Tomcat处理servlet和jsp相关的文件 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> D. logs 存放Tomcat的日志文件 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> E. temp 存放tomcat运行时产生的临时文件 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> F. webapps当发布web应用程序时通常把web应用程序的目录及文件放到这个目录下 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> G. work Tomcat将JSP生成的servlet源文件和字节码文件放到这个目录下 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">第一次在</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Tomcat</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">下创建项目</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在tomcat的webapps目录下 , 创建一个文件夹 , 命名为day01 , 然后在里面创建一个html文件 , 随便写上一些内容 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们启动Tomcat服务器 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 文件的路径为 : E:\DevelopPakage\apache-tomcat-6.0.35\webapps\day01</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在浏览器中我们输入</span> <span style="color:#000000; word-wrap:break-word"> : </span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/day01/1.html</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#000000; word-wrap:break-word">就能访问到刚才创建的html文件</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这就说明了一个问题</span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#000000; word-wrap:break-word">与E:\DevelopPakage\apache-tomcat-6.0.35\webapps\ 映射是一样的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#000000; word-wrap:break-word">对应的是Tomcat服务器的webapps目录 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">在</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Tomcat</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">中打开</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Jsp</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">页面</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">浏览器</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">Jsp</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">页面生成的原理</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">)</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">在MyEclipse中创建一个Web项目 , 从中将Jsp复制到刚才在webapps文件夹下创建的day01文件夹下 , 然后在浏览器中输入</span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/day01/index.html</span> <span style="color:#000000; word-wrap:break-word"> , </span> <span style="color:#000000; word-wrap:break-word">就能访问到这个页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">我们在浏览器中打开源文件 , 在打开Jsp的源文件 , 发现两个源文件并不是完全一模一样的 , 其中有很多地方有改动 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Jsp页面源码发生改变的原因:</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. 在work文件夹下存放的是Jsp生成的servlet源文件和字节码文件 , Jsp页面并不是直接就能在浏览器中显示出来 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">B. 打开E:\DevelopPakage\apache-tomcat-6.0.35\work\Catalina\localhost\day01\org\apache\jsp 目录 , 下面有两个文件 , 分别是index_jsp.class 和index_jsp.java , 其中的index_jsp.java 中的程序中有很多行的 out.write() , 浏览器中的代码就是这里的Java代码一行一行写出来的 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:12pt">(4)Tomcat Manager </span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">的使用</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. 如果查看当前的所有项目的信息 , 我们可以再Tomcat中查看这些信息 , Tomcat Manger 在我们使用</span> <span style="color:#000000; word-wrap:break-word"></span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#000000; word-wrap:break-word">在浏览器中登陆的页面 , 选择在小猫下的第二个连接就是 Tomcat Manager , 但此时我们登陆的时候需要账号密码才能登陆 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">B. 设置登陆口令</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在弹出的口令的界面 , 我们连续点3次确定 , 就会跳入一个界面 , 在这个界面给我们一个建议 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们按照建议操作 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 进入conf目录下的tomcat-user.xml文件中 , 在<tomcat-users> 标签中添加下面的内容</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <role rolename="manager-gui"/></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><user username="admin" password="admin" roles="manager-gui"/></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">rolename 是管理权限 , 这里有四种权限 , manager-gui是最高的权限 . 在第二行的标签中我们设置了账号和密码 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">四种权限介绍 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">manager-gui</span> - allows access to the HTML GUI and the <span style="word-wrap:break-word">status pages(状态页)</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> </span>允许访问管理页面和状态信息页面</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">manager-script</span> - allows access to the text interface and the status pages</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> </span>允许访问文本接口和状态信息页面</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">manager-jmx</span> - allows access to the JMX proxy and the status pages</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> </span>允许访问Java管理扩展代理和状态信息页面</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">manager-status </span>- allows access to the status pages only</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> </span>允许访问状态信息页面</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> </span>C. 管理页介绍</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">进入的Tomcat manager 界面是对所有webapps下的项目的管理页 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">1)其中的/doc 是Tomcat的文档 , 我们可以在这里查询Tomcat 相关的文档,信息 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">2)我们点击我们的/day01 项目 , 发现会进入 index.jsp 页面 , 这是因为在conf 目录下的web.xml 中设置了欢迎文件 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在web.xml中有这样一个标签(1220行) :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <welcome-file-list></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <welcome-file>index.html</welcome-file></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <welcome-file>index.htm</welcome-file></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <welcome-file>index.jsp</welcome-file></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </welcome-file-list></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">在这里设置了项目的欢迎文件 , 欢迎文件当我们打开一个项目的时候 , 第一个弹出的页面 , 根据上面的标签 , 我们可以了解到 : 在打开一个项目的时候 , 会首先查看有没有index.html文件 , 有的话就作为欢迎文件 , 没有的话就去找 index.htm 文件作为欢迎文件 , 如果在没有就去找index.jsp作为欢迎文件 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十</span><span style="font-family:Times New Roman; word-wrap:break-word"> Java EE </span><span style="font-family:宋体; word-wrap:break-word">体系结构</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">客户层</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 包含于用户交互的程序 , 这些程序提示用户进行输入 , 然后把用户的响应转化成请求 , 发往到服务端组件 , 并接收服务端处理的结果 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">表示层</span><span style="font-family:Arial; word-wrap:break-word">(web</span><span style="font-family:黑体; word-wrap:break-word">层</span><span style="font-family:Arial; word-wrap:break-word">)</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 为Java EE 应用程序提供Internet功能 , 在Web层运行的组件 , 使用http协议接收客户端的各种请求 , 并将对请求的响应返回给客户端 . 例如 Servlet , jsp .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. </span><span style="font-family:黑体; word-wrap:break-word">业务层</span><span style="font-family:Arial; word-wrap:break-word"></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 包含javaEE应用程序的业务路几层 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 4. EIS</span><span style="font-family:黑体; word-wrap:break-word">层</span><span style="font-family:Arial; word-wrap:break-word">(</span><span style="font-family:黑体; word-wrap:break-word">信息系统层</span><span style="font-family:Arial; word-wrap:break-word">)</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 是JavaEE应用程序与其它技术的直接或者间接接口 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十一</span><span style="font-family:Times New Roman; word-wrap:break-word"> Servlet</span><span style="font-family:宋体; word-wrap:break-word">简介</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">什么是</span><span style="font-family:Arial; word-wrap:break-word">Servlet</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. Java编写的服务器端程序</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 主要功能在于交互式的浏览和修改数据 , 生成动态web内容 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 狭义的servlet是指Java语言实现的一个接口 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 广义的servlet是指任何实现了这个Servlet接口的类别 , 一般情况下按照广义理解 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. Servlet运行于支持Java的服务器中 . 从现实上讲 , Servlet可以响应任何形式(ftp,svn等类型也可以)的请求 , 但绝大多数情况下servlet只用来扩展基于http协议的web服务器 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. Servlet</span><span style="font-family:黑体; word-wrap:break-word">的优缺点</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (1) 优点</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (2) 缺点</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. Servlet</span><span style="font-family:黑体; word-wrap:break-word">容器就是</span><span style="font-family:Arial; word-wrap:break-word">Tomcat </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十二</span><span style="font-family:Times New Roman; word-wrap:break-word"> Servlet</span><span style="font-family:宋体; word-wrap:break-word">运行过程</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">浏览器发出请求</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Web浏览器向Web容器发出http请求 , 之后Web容器会创建Servlet , 只有首次访问才创建Servlet ;</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">创建</span><span style="font-family:Arial; word-wrap:break-word">servlet</span></span><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">创建请求</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(request)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">和响应</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(response)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">对象</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 此时Web容器会创建请求和响应对象 , 并将相应的数据填充进去 , 创建的请求头和请求体有实际的数据填充 , 但是响应头和响应体都为空 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 请求有7中 , 分别是 get , post , put , delete , head , option .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">调用</span></span><span style="word-wrap:break-word; font-size:12pt"><span style="font-family:Times New Roman; word-wrap:break-word">service</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:12pt">方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Service方法是servlet的一个方法 , 这个方法读取请求信息 , 并向空白的响应头和响应体写入响应信息 , 并生成servlet ;</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. </span><span style="font-family:黑体; word-wrap:break-word">浏览器收到响应</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Servlet的service方法将servlet返回给Web容器 , Web容器在读取响应信息 , 并向Web浏览器发出http响应 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十三</span><span style="font-family:Times New Roman; word-wrap:break-word"> Servlet</span><span style="font-family:宋体; word-wrap:break-word">编程</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 1. </span><span style="font-family:黑体; word-wrap:break-word">配置</span><span style="font-family:Arial; word-wrap:break-word">Servlet</span><span style="font-family:黑体; word-wrap:break-word">虚拟路径</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">配置路径原理</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">浏览器是通过URL地址来访问Web服务器的资源 , 如果servlet程序想要被外界访问 , 必须将servlet程序映射到一个URL地址上 , 这个工作在WebRoot | WEB-INF | 中的web.xml中完成 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">如何配置</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Servlet是通过两组标签来完成虚拟路径的配置的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> A. <servlet>标签用来注册Servlet , 其主要包含两个子元素 , <servlet-name>和<servlet-class> , 前者用于设置Servlet注册名称 , 后者用来存放Servlet完整类名 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. <servlet-mapping> 用于映射一个已注册的Servlet的一个对外访问路径 , 它包括<servlet-name>和<url-pattern>两个子标签 , 分别用于指定注册名称和对外访问路径 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">配置实例</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <web-app></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name>ServletDemo</servlet-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-class>cn.itcast.servlet.ServletDemo</servlet-class></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-mapping></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name>ServletDemo</servlet-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <url-pattern>/servletdemo</url-pattern></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet-mapping></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </web-app></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 假设我们的工程名字叫day05 , 那么我们使用</span> <span style="color:#000000; word-wrap:break-word"> </span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/day05/servletdemo</span> <span style="color:#000000; word-wrap:break-word"> , </span> <span style="color:#000000; word-wrap:break-word">就可以访问刚才的servlet页面了 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(4)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">虚拟路径访问过程</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">浏览器中端口工程名后面跟着 url , 在服务器中会自动根据 url 到web.xml 文件中查找 <servlet-mapping> 标签的<url-pattern> , 如果找到匹配的 , 找到本<servlet-mapping>标签下的<servlet-name> , 在去<servlet> 标签中找到相应的<servlet-name> 符合的标签 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(5)servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">与</span></span><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">servlet-mapping</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">可以一对多</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 同一个servlet可以被映射到多个URL上 , 即多个<servlet-mapping>元素的<servlet-name>子元素的设置 , 可以使同一个servlet注册名 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(6)servlet-mapping</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">中的</span></span><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">url-pattern </span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">可以使用通配符</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Servlet映射到url中可以使用 * 通配符 , 但是只能由两种固定的格式 : 一种格式是 *.扩展名 ; 另一种是以 / 开头 , 并以 /* 结尾 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 总结 : 只能使用 / 或 * 开头 , *开头的时候后面就没东西了 ; / 和 *. 不能同时存在 ( 意思是/*.不行 ) ; / 或 /* 表示任意 ; 只有 *. 才表示通配符 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 2. </span><span style="font-family:黑体; word-wrap:break-word">创建一个简单的</span><span style="font-family:Arial; word-wrap:break-word">Servlet</span><span style="font-family:黑体; word-wrap:break-word">程序</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">创建一个</span></span><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">Web Project</span></span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">创建</span></span><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">页面</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. 包名填写 my.cn.itcast , 名字上填写 hello , 修饰符选择 public , MyEclipse自动选好了继承的父类 javax.servlet.http.HttpServlet , 我们就不需要选了 , 选择一个要用的模板 Default temple for Servlet , 创建的方法勾上 doGet() 和 doPost() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">B. 进入创建的第二页 , ClassName不能修改 , 这是我们之前输入好的 , 在此不作修改 , name 和 maping url 可以直接设置web.xml文档中的信息 , 那么相当于<servlet-name>标签中的信息 , mapping url 相当于 <url-pattern>标签中的信息 , 第三个是设置的创建servlet文件的路径 , 第四第五个是描述信息 , 可写可不写 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">C. 创建好了之后 , 我们去查看web.xml文件的配置 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <description>This is the description of my J2EE component</description></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <display-name>This is the display name of my J2EE component</display-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name>Hello</servlet-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-class>my.cn.itcast.Hello</servlet-class></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-mapping></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name>Hello</servlet-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <url-pattern>/servlet/Hello</url-pattern></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet-mapping></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 其中的<servlet>标签下的<description>和<display-name> 是我们创建servlet第二页设置的最后两项 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">D. 发布servlet并启动Tomcat</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 选中项目 , 然后选择发布按钮 , 左边的是发布按钮 , 右边的是启动Tomcat按钮 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在Project选项中选择项目 , 然后点右侧的Add添加Tomcat , 然后点右侧的Redeploy发布 , 在最下面的信息框中出现successfully deployed , 说明发布成功 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 然后点ok退出 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">E. 打开浏览器 , 在浏览器地址栏输入</span> <span style="color:#0000ff; word-wrap:break-word">http://localhost:18080/day05_exercise/servlet/Hello</span> <span style="color:#000000; word-wrap:break-word"> , </span> <span style="color:#000000; word-wrap:break-word">就可以访问这个Servlet页面</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 3. Servlet</span><span style="font-family:黑体; word-wrap:break-word">页面中的乱码问题</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">乱码现象</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在上面的页面中添加 out.println(“中文”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 就会在生成的html页面中将 “中文” 两个字添加进去 , 但是我们添加进去的时候 , 在浏览器中显示的是乱码 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(2)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">产生乱码的原因</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Servlet源文件中直接输出 “中文” 两个汉字 , 这些信息发送到Tomcat服务器之后 , Tomcat就会按照ISO-8859-1 进行转码 , 显然 , 转码以后就变成了乱码 , ISO-8859-1码表中没有中文 , 只有英文 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">“中文” à 按照ISO-8859-1编码 à “??”</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">解决乱码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String str = “中文” ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> str = new String( str.getBytes(“GBK”) , “ISO-8859-1” ) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 由于浏览器默认的码表为GBK , 我们最终得到的字符串是用GBK解析的 , 我们直接得到 “中文” 的GBK码表数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 将GBK格式的字符串使用 “ISO-8859-1”进行编码得到一个新的字符串 str , 将这个str发送到Tomcat服务器进行解析 , Tomcat将会用 “ISO-8859-1” 对齐进行解析 , 得到的是原来的 GBK码的字符串 , 浏览器最终用GBK码表解析这个字符串 , 我们最终能够看到中文 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 4. servlet</span><span style="font-family:黑体; word-wrap:break-word">注册和编写映射</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1) servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">注册</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 使用servlet标签实现servlet注册 , 注册的目的是将servlet提供给别人使用 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name> 为自己起名 , 命名自定义 , 但不能重复 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-calss> 选择要注册的servlet的完整路径 , 这个class路径从源文件的包名开始 , 到不带后缀的servlet文件名 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如: 如果servlet是在cn.itcast 包下的 Servlet.java , 那么此时的<servlet-calss> 中的路径为 cn.itcast.Servlet .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">(2) servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">配置初始化</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">在Servlet的配置文件中 , 可以使用一个或多个<init-param>标签为servlet配置一些初始化 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在web.xml文档中 , 注册servlet的时候 , 在<servlet>标签中除了有<servlet-name>和<servlet-calss>子标签之外 , 还可以有*个<init-param> 标签 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 初始化参数设置 , 设置一个参数名和参数值 , 参数名<param-name>和参数值<param-value>是<init-param>的子标签 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 例如 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <init-param></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <param-name>ServletName</param-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <param-value>ServletContex</param-value></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </init-param></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面在servlet中设置了初始化参数 , 参数名为 servletname , 参数值为 ServletContex .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(3)</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">编写映射</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 编写映射就是配置虚拟路径 , 详见四 Servlet编程 | 1. 配置servlet虚拟路径 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 5. init</span><span style="font-family:黑体; word-wrap:break-word">方法中的</span><span style="font-family:Arial; word-wrap:break-word">ServletConfig</span><span style="font-family:黑体; word-wrap:break-word">对象</span><span style="font-family:Arial; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1) </span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">配置初始化参数</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">在Servlet配置文件中 , 可以使用一个或多个<init-param>标签 , servlet配置一些初始化参数 , 详见上面 4 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">(2) </span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">如何获得初始化信息</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">当servlet配置了初始化参数后 , web容器在创建servlet实例对象时 , Tomcat会自动将这些初始化参数封装到ServletConfig对象中 , 并在调用Servlet的init()方法的时候 , 将ServletConfig对象传递给servlet , 进而 , 程序员就可以通过ServletConfig对象就可以得到当前的servlet初始化信息 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt"><span style="font-family:Times New Roman; word-wrap:break-word">(3)ServletConfig API</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ServletConfig接口定义了一个对象 , 通过这个对象 , Servlet容器允许Servlet获得一个有关ServletContex接口说明 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word">A. getInitParameteerNames()</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public Enumeration getInitParamNames() , 这个方法返回一个枚举集合 , 其中放的是String对象 , 这些字符串是初始化的参数名 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Enumeration就是老版本的迭代器 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">Enumeration</span>有两个方法 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">HasMoreElements()</span> , 返回一个布尔类型 , 是否有下一个元素 , 如果有就返回true , 反之返回false .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">nextElement()</span> , 返回下一个枚举 , 返回的是枚举中的元素 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个枚举的使用方法 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Enumeration<String> names = config.getInitParameterNames() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> While ( names.hasMoreElements() ){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String name = names.nextElement() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> System.out.println( name ) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">上面的代码可以将所有的参数打印出来 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word">B. getInitParameter()</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public String getInitParameter(String str) , 返回初始化参数名为str所对应的参数值 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">C. getServletContex()</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Public ServletContex getServletContex() , 返回这个servlet的ServletContex对象 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 获得上下文对象 , 一个项目只有一个该对象 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 以后会讲 , 关于四大作用域 , ServletContex是最大的作用域 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">D. getServletName()</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 返回的是一个字符串 , 如果这个servlet文件的文件名是ServletDemo.java , 那么返回的就是 ServletDemo .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 4. Servlet</span><span style="font-family:黑体; word-wrap:break-word">生命周期</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1) init()</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">服务器调用该方法初始化servlet , 该方法只在servlet第一次被请求加载的时候调用一次 , 当有客户在请求servlet服务时 , 这个方法就不再执行了 , 服务器将启动一个新的线程 , 在该线程中 , 调用service方法响应用户的请求 ;</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(2) service()</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 初始化完毕 , 服务器调用该方法响应客户的请求 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(3) destroy()</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 服务器调用该方法消灭servlet .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 5. </span><span style="font-family:黑体; word-wrap:break-word">配置</span><span style="font-family:Arial; word-wrap:break-word">Servlet</span><span style="font-family:黑体; word-wrap:break-word">自动加载</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果在web.xml文件中 , 在注册servlet的时候 , 在其子标签配置了一个<load-on-startup>元素 , 那么Web应用程序在启动时 , 就会装载并创建Servlet实例对象 , 以及调用Servlet实例对象的init()方法 . 设置了自动加载 , 这个servlet就会在服务器启动的时候就会加载 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">例如 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-name>invoker</servlet-name></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <servlet-class></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> org.apache.catalina.servlets.InvokerServlet</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet-class></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <load-on-startup>2</load-on-startup></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </servlet></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">在上面的servlet注册标签中 , 除了servlet-name 和 servlet-calss 两个子标签外 , 还有一个 load-on-startup 标签 , 这个标签值为 0 – 6 , 数字越小优先级越高 , 配置的时候 , 那个数字越小 , 服务器启动的时候就先加载哪一个 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 6. </span><span style="font-family:黑体; word-wrap:break-word">错误页面替换</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们使用浏览器浏览页面的时候 , 会出现各种错误 , 为了使界面友好 , 我们使用一些出错页替换相应的错误码页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在WebRoot目录下创建一个error文件夹 , 在里面创建相应错误的Jsp页面 , 一般都用错误码.jsp 作为出错页面 , 例如错误404 相应的页面 404.jsp .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 然后在 web.xml 文档中加入以下标签 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <error-page></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <error-code>404</error-code></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <location>/error/404.jsp</location></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </error-page></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 当我们访问出现404错误之后 , 就会自动跳转到这个页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果我们使用html页面作为出错页面 , 但是IE浏览器会过滤html页面 , 需要在IE | Internet 选项中选中显示友好的错误信息 , 这样就能显示html出错页面了 , 正因为这样我们不适用html页面作为出错页面 , 我们使用jsp页面作为出错页面 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 7. </span><span style="font-family:黑体; word-wrap:break-word">缺省</span><span style="font-family:Arial; word-wrap:break-word">servlet</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果某个servlet的映射路径仅仅为一个正斜杠(/) , 那么这个Servlet就成为当前web应用程序的的缺省servlet .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 凡是在web.xml 文件中找不到匹配的<servlet-mapping>元素的url , 它们的访问请求都将交给缺省的servlet处理 , 也就是说 , 缺省Servlet处理用于处理其他servlet都不处理的访问请求 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 8. Servlet</span><span style="font-family:黑体; word-wrap:break-word">接口实现类</span><span style="font-family:Arial; word-wrap:break-word"> </span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(1)Servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">接口简介</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">A. SUN公司为Servlet接口定义了两个实现类 , GenericServlet 和 HttpServlet , GenericServlet 是 HttpServlet的父类 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> B. Servlet是一个接口 , 所有的servlet都必须实现这个接口 , 或者是实现这个Servlet接口的子类 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> C. GenericServlet类实现了Servlet接口 , 有一点要注意 , GenericServlet类不是Servlet的子类 , 它是Object的子类 .<span style="word-wrap:break-word">---?</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> D. HttpServlet类继承了GenericServlet类 , 是GenericServlet类的子类 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"> </span><span style="word-wrap:break-word; font-size:14pt">(2)Servlet</span></span><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:14pt">类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">A. 介绍</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个接口定义了一个Servlet , Servlet是一个在Web服务器上继承了这个功能的java类 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">B. 方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 1) <span style="word-wrap:break-word">init()方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Public void init(ServletConfig config) throws ServletException</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 被servlet容器调用 , 表名一个servlet被置入服务 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个方法是在浏览器访问servlet的java类之后 , 调用service()方法之前执行的 , 在服务器启动之后 , 该init()方法只调用一次 , 并且在调用service之前必须退出 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 2) <span style="word-wrap:break-word">service()方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Servlet容器调用这个方法 , 允许servlet响应请求 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 3) <span style="word-wrap:break-word">destroy()方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Servlet容器调用这个方法 , 将servlet从服务器中移出 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 4) <span style="word-wrap:break-word">getServletConfig()方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 返回一个ServletConfig对象 , 这个对象包括这个这个servlet的初始化和启动参数 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 5) <span style="word-wrap:break-word">getServletInfo()方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 返回这个servlet信息 , 例如作者 , 版本 , 版权等信息 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (3)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (3) GenericServlet实现类</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> (3) HttpServlet实现类</span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> </span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十四</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">四大作用域</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span></span><span style="font-family:Arial; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> 1. Context</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 一个应用(项目)拥有唯一的一个ServletContex对象 , 访问此应用的任何浏览器 , 共享一个ServletContex .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 一个应用是从服务器开启 , 到服务器关闭 , 指的是一个项目 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 获取方式 , servletConfig.getServletContex()方法 ,</span> </div> <span style="word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> 2. session</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 为每一个浏览器创建一个独有的会话 , 当前的用户访问任意的servlet都可以保存自己的数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 类 : HttpSession , 获取该类的方式 , httpServletRequest.getSession() .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 每一个HttpSession对象都有自己唯一的ID值 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> 3. request</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 用户请求Servlet , 当请求结束的时候request消失 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 类 HttpServletRequest .</span> </div> <span style="word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> 4. PageContext</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 5. </span><span style="font-family:黑体; word-wrap:break-word">相同点</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ServletContex , HttpSession , HttpServletRequest 三个类都有以下两种方法 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">setAttribute(key , value)</span> , 用于将数据存在此范围内 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">getAttribute(key)</span> , 用于将数据从某范围内取出 .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"> 6. </span><span style="font-family:黑体; word-wrap:break-word">比较</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ServletContex , HttpSession , HttpServletRequest , PageContext 作用范围依次减小 , 但它们没有包含关系 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ServletContex一个项目中有一个 , HttpSession 一个会话有一个 , HttpServletRequest 一次请求有一个 , PageContext 一个页面有一个 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十五</span><span style="font-family:Times New Roman; word-wrap:break-word"> jdbc</span><span style="font-family:宋体; word-wrap:break-word">入门</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1.jdbc</span><span style="font-family:黑体; word-wrap:break-word">概念</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Jdbc Java Database Connectivity .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这是Sun公司的对数据库进行操作的一套<span style="word-wrap:break-word">api</span> , 都是由<span style="word-wrap:break-word">接口</span>组成 , Sun公司没有实现 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这些接口都是由数据库厂商进行实现的 , 这些<span style="word-wrap:break-word">实现的类</span> , 我们称之为<span style="word-wrap:break-word">驱动</span> .</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2.jdbc</span><span style="font-family:黑体; word-wrap:break-word">步骤详解</span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(1). </span><span style="font-family:宋体; word-wrap:break-word">注册驱动</span></span></span></span> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">DriverManger类介绍 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">DriverManger使java.sql包下的类 , 作用使管理jdbc驱动用的 , 下面用到了DriverManger类的集中方法 , 其中 registerDriver()为注册驱动程序 , getConnection()为获得数据库连接 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">DriverManager.registerDriver( new com.mysql.jdbc.Driver() ) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面的语句会导致驱动加载两次 , com.mysql.jdbc.Driver 中由一个静态的代码块 , 该代码块中的语句是<span style="word-wrap:break-word">java.sql.DriverManager.registerDriver(new Driver());</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在com.mysql.jdbc.Driver()中的静态代码块就将该驱动注册了 , 我们只需要加载这个类就可以了 , 不用在外部在使用一次 DriverManager.registerDriver(new com.mysql.jdbc.Driver())了 , 这样在静态代码块中加载了一次驱动 , 在外部我们又执行了一次加载 , 这样驱动就加载了两次了 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们只需要使类加载就可以了 , 我们使用 Class.forName(“com.mysql.jdbc.Driver”); 就可以实现驱动的注册了 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(2)</span><span style="font-family:宋体; word-wrap:break-word">创建数据库的连接</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connection conn = DriverManager.getConnection(url , user , password) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面是获得数据库连接的语句 , Connecttion对象就是数据库的连接 , 我们使用java.sql.DriverManger下的getConnection()方法可以获取数据库连接 , 传入的三个值都是字符串形式的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">1)url : 是数据库的地址 ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 格式范例 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">jdbc:mysql://localhost:3306/test?参数名1=参数值1&参数名2=参数值2</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">url个字段介绍 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> jdbc : 主协议</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> mysql : 子协议</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> localhost : 主机名 , 可以为ip地址</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 3306 : 数据库的端口号</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Test : 数据库名称</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 参数名和参数值常为数据库的用户名 , 密码或者编码类型 , 常用的参数示例 user=root&password=root&characterEncoding=UTF-8</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">2)user :</span> 是数据库的用户名</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">3)password :</span> 数据库的密码</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果在url中带了用户名和密码的参数 , 可以不写 user和password .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getConnection()可以传入两种参数 , 一个是 url , user, password 三个参数 ; 另一种是传入一个带用户名和密码的uri .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = DriverManger.getManager(“jdbc:mysql://localhost:3306/test” , root , root) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = DriverManger.getManager(“jdbc:mysql://localhost:3306/test?user=root&password=root”);</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(3)</span><span style="font-family:宋体; word-wrap:break-word">几个重要的类及其主要方法</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1)Connecttion</span><span style="font-family:黑体; word-wrap:break-word">类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 作用 : Connecttion对象用于表示对某个数据库的连接 , 所有的对数据库的操作都需要Connecttion对象来完成 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> createStatement() 创建向数据库发送sql语句的数据库对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> <span style="word-wrap:break-word">prepareStatement(sql) </span> <span style="color:#000000; word-wrap:break-word">创建向数据库发送预编译sql的PrepareStatement对象 ;</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2)Statement</span><span style="font-family:黑体; word-wrap:break-word">类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 作用 : 用于向数据库发送sql语句并返回生成的结果对象.</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Execute(String sql) 用于向数据库发送任意sql语句 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> executeQuery(String sql) 用于向数据库中发送查询sql语句 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> executeUpdate(String sql) 用于向数据库总发送增删改sql语句;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面的三个方法返回的都是ResultSet对象 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">3)PreparedStatement</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 作用 : 表示预编译的sql语句对象 , 也有Statement对象的三个方法 , 方法遇上面的Statement对象方法基本相同 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">4)ResultSet</span><span style="font-family:黑体; word-wrap:break-word">类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 作用 : 这个类的对象用于封装查询到的结果集 , 这个结果与我们看到的dos窗口查询到的结果一样 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 指针一开始指向的位置是第一行 , 就是表头 , 第一行只是列名 , 没有数据 , 取出数据要从第二行开始 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Next() : 指针指向下一行 , 如果没有下一行就返回false , 如果有就返回true ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">get()方法 </span>, 当我们将指针指向一行的时候 ,可以获取当前行某列的数据 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getBoolean()方法 , 获得数据库中的bit类型的数据 , 返回类型为boolean ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getByte()方法 , 获得数据库中的tinyint类型的数据 , 返回类型为byte ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getShort()方法 , 获得数据库中的smallint类型的数据 , 返回类型为short ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getInt()方法 , 获得数据库中的int类型的数据 , 返回类型为int ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getLong()方法 , 获得数据库中的bigint类型的数据 , 返回类型为long ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getString()方法 , 获得数据库中的char , varchar , longvarchar类型的数据 , 返回类型为String ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getClob()方法 , 获得数据库中的clob类型的数据 , 返回类型为clob ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getBlob()方法 , 获得数据库中的blob类型的数据 , 返回类型为blob ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getDate()方法 , 获得数据库中的date类型的数据 , 返回类型为java.sql.Date ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getTime()方法 , 获得数据库中的time类型的数据 , 返回类型为java.sql.Time ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getTimeStamp()方法 , 获得数据库中的timestamp类型的数据 , 返回类型为java.sql.Timestamp ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 其中可以将列的信息当作参数传入上面的get方法中 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> get(int index) 获得第几列的数据, 列数从1开始 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> get(String columnName) 根据列名获得 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> previous() : 指针移到上一行 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> absolute(int index) : 移到指定行 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> beforeFirst() : 移动到ResultSet的最前面 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> afterLast() : 移动到ResultSet的最后面 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">用上面三个类处理对数据库的各种操作以及获得的结果 .</span></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(4)</span><span style="font-family:宋体; word-wrap:break-word">释放数据库资源</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面用于数据库连接和操作以及结果处理创建的对象必须要释放掉 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 需要释放的对象 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Connecttion对象 conn , 这个对象必须释放掉 , 因为数据库有并发连接数 , 如果一个连接没有释放 , 就会被占用这个连接 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Statement 对象 stmt ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet 对象 rs ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面的三个对象都需要释放掉 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 将释放对象的语句放在finally语句中</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> 语释放语句技巧 , 先判断是否为空 , 如果不为空我们就将其关闭 , 如果出现异常 , 打印之 , 执行完之后将conn=null ;</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> If(conn != null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Conn.close()</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(SQlException e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> E.printStackTrace();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> If(stmt != null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt.close()</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(SQlException e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> E.printStackTrace();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">stmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> If(rs != null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs.close()</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(SQlException e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> E.printStackTrace();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">下面是</span><span style="font-family:Times New Roman; word-wrap:break-word">jdbc</span><span style="font-family:宋体; word-wrap:break-word">案例</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">十六</span><span style="font-family:Times New Roman; word-wrap:break-word"> JDBC</span><span style="font-family:宋体; word-wrap:break-word">案例介绍</span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1.</span><span style="font-family:黑体; word-wrap:break-word">需求</span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">实现一个简单的员工信息管理系统 , 并实现对其的增删改查</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">id varchar(40)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">name varchar(20) </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">gender varchar(4)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">birthday date</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">idcard varchar(20)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">degree vachar(20)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">entrydate date</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">position varchar(40)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">department varchar(20)</span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2.</span><span style="font-family:黑体; word-wrap:break-word">步骤简介</span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(1)</span><span style="font-family:宋体; word-wrap:break-word">模式选择</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> java开发两种模式 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> jsp+javabean 只适合小型应用 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> servlet + jsp + javabean mvc模式 jsp 用来显示 , 其中禁止调用方法 , 调用的方法都放在servlet中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这里我们选择mvc模型 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(2)</span><span style="font-family:宋体; word-wrap:break-word">搭建开发环境</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 1) 建工程建包</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 2) 导入相关jar包</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> BeanUtils先关jar包 commons-beanutils-1.8.0.jar 和 commons-logging.jar</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> jstl标签库 (这个包是自带的)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> mysql 相关jar包 mysql-connector-java-5.0.8-bin.jar</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 将上面的三个包复制到WEB-INF下面的lib文件夹下 , MyEclipse会自动将路径加到工程上 . 这个lib文件夹是工程自带的 . </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 3)创建数据库和表</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word">create database day12_employee;</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> use day12_employee;</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> create table employee</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> (</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> id varchar(40) primary key,</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> name varchar(20),</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> gender varchar(6),</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> birthday date,</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> idcard varchar(20),</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> degree varchar(20),</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> entrydate date,</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> department varchar(20),</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> position varchar(40)</span></span> </div> <div style="word-wrap:break-word"> <span style="font-family:Times New Roman; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> );</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(3)</span><span style="font-family:宋体; word-wrap:break-word">设计</span><span style="font-family:Times New Roman; word-wrap:break-word">bean</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> employee.java</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(4)</span><span style="font-family:宋体; word-wrap:break-word">实现</span><span style="font-family:Times New Roman; word-wrap:break-word">dao</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(5)</span><span style="font-family:宋体; word-wrap:break-word">实现</span><span style="font-family:Times New Roman; word-wrap:break-word">service</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">简单的原封不动的调用dao中的方法</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(6)</span><span style="font-family:宋体; word-wrap:break-word">实现</span><span style="font-family:Times New Roman; word-wrap:break-word">web</span><span style="font-family:宋体; word-wrap:break-word">层</span><span style="font-family:Times New Roman; word-wrap:break-word"> .</span></span></span><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">3</span><span style="font-family:黑体; word-wrap:break-word">按照步骤进行详解</span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(1)</span><span style="font-family:宋体; word-wrap:break-word">设计</span><span style="font-family:Times New Roman; word-wrap:break-word">javabean</span></span></span></span> <div style="word-wrap:break-word"> 创建一个cn.itcast.myemp.domain 包 , 我们在后面包名统一前面加上 cn.itcast.myemp ; </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1)employee</span><span style="font-family:黑体; word-wrap:break-word">实体类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">将上面的九个字段一一实现 , 获得getter setter方法即可 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String id; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String name; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String gender; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String idcard; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String degree; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String department; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> String position; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> Date birthday; </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> Date entrydate; </div> <div style="word-wrap:break-word"></div> <div style="word-wrap:break-word"> 注意这个Date导入的是 java.util.Date包 </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2)Page</span><span style="font-family:黑体; word-wrap:break-word">实体类</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private</span> <span style="word-wrap:break-word">List</span> pageData; // 分页显示的数据 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> pageNum; // 当前页码 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> totalRecord; // 总记录数 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> totalPageNum; // 总页数 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> firstPageNum; // 起始页码 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> lastPageNum; // 结束页码 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 设置上面的一系列私有变量 , 获得getter和setter方法 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(2)</span><span style="font-family:宋体; word-wrap:break-word">创建配置文件</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在src下创建一个jdbc.properties 的文件</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 输入以下数据</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> driverClass=</span>com.mysql.jdbc.Driver </div> <div style="word-wrap:break-word"> uri=jdbc:mysql://localhost:3306/emp </div> <div style="word-wrap:break-word"> user=root </div> <div style="word-wrap:break-word"> password=root </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 上面的四行是数据库连接相关的数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个配置文件的四个键值对是jdbc的四要素 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(3)</span><span style="font-family:宋体; word-wrap:break-word">实现工具类</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1)WebUtils</span><span style="font-family:黑体; word-wrap:break-word">工具类</span><span style="font-family:Arial; word-wrap:break-word"> </span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">request2Bean()</span><span style="font-family:宋体; word-wrap:break-word">方法的概述</span><span style="font-family:Times New Roman; word-wrap:break-word"> :</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 先创建一个实体类对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 注册转换器 , 如果我们需要自动转换类型就需要这一步 , 在调用BeanUtils.setProperty()方法的时候会自动调用</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 获得request中的参数名枚举 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 遍历枚举 , 获得参数名和参数值 , 然后调用 BeanUtils.setProperty()方法 , 将参数值按照参数名封装到bean实体类中 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 返回封装好的bean实体类 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">注册日期转换器</span><span style="font-family:Times New Roman; word-wrap:break-word"> :</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 先创建一个日期转换器对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 设置这个转换器对象的格式 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 注册这个转换器 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> a. </span><span style="font-family:宋体; word-wrap:break-word">先私有化构造函数</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> private WebUtils(){}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 然后创建两个方法 request2Bean()方法和 forward()方法 , 一个是用来将表单提交数据封装到javabean中 , 第二个是转发全据消息页面 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> b. </span><span style="font-family:宋体; word-wrap:break-word">创建</span><span style="font-family:Times New Roman; word-wrap:break-word">request2Bean()</span><span style="font-family:宋体; word-wrap:break-word">方法</span><span style="font-family:Times New Roman; word-wrap:break-word"> :</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public static <T> T request2Bean(HttpServletRequest request , Class<T> beanClass ){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> //先创建一个bean对象 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> T bean = beanClass.newInstance();</span> </div> <div style="word-wrap:break-word"> //封装一个uuid作为其id , 这里是为了使id不会重复 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> BeanUtils.setProperty(bean , “id” , UUID.radomUUID().toString());</span> </div> <div style="word-wrap:break-word"> //注册转换器 , 这个转换器可以在调用BeranUtils.setProperty()方法的时候 , 自动调用 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> DateConvert convert = new DateConvert();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> convert.setPattern(“yyyy-MM-dd”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ConvertUtils.register(convert , Date.class) </span>//由字符串转换为date的时候调用这个方法 . </div> <div style="word-wrap:break-word"> //获得request中的参数名枚举 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Enumeration e = request.getParameterNames();</span> </div> <div style="word-wrap:break-word"> //便利枚举 , 并调用request.getParameter()方法得到参数值 , 再将参数封装到bean中 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> while(e.hasMoreElement){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String name = (String)e.nextElement();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String value = request.getParameter(name);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> BeanUtils.setProperty(bean , name , value);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> //将bean返回 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return bean ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> throw new RuntimeException(e);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> c. </span><span style="font-family:宋体; word-wrap:break-word">转发全据消息页面方法</span><span style="font-family:Times New Roman; word-wrap:break-word"> :</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> <span style="word-wrap:break-word">注意转发的时候的路径是绝对地址 , 从应用的根目录开始 , / 表示应用的根目录 , 页面是在根目录下的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public static void forward(HttpServletRequest request , HttpServletResponse response , String message) throws ServletException , IOException{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> request.setAttribute(“message” , message);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> request.getRequestDispatcher(“/WEB-INF/pages/message.jsp”).forward(request , response);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">WebUtils</span><span style="font-family:宋体; word-wrap:break-word">工具类是否可用</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 验证request2Bean()方法可行性 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> a. 一个jsp页面不能跳转到另一个jsp页面 , 如果想要跳转 , 必须使用一个UiServlet进行跳转 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> b. 在首页中创建一个链接 , 直接链接到 “${pageContext.request.contextPath}/servlet/UiWebUtilsTest” ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> el表达式不用导入标签库就可以使用 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">servlet/UiWebUtilsTest是一个中转页面 , 在这个页面中只有一句</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">request.getRequestDispatcher(“/WEB-INF/pages/webutilstest.jsp”).forward(request , response)语句 , 直接跳转到测试页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 创建一个Person类 , 有三个属性 name , birtjday , age ; 从表单提交这三个属性 , 其中birthday是Date类型的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. wenutilstest.jsp表单页 , 提交上面三个属性到WebUtilsTest页面 , 调用WebUtils.request2questBean()方法 , 看是否能将表单中的数据封装到Person实体类中 , 包括日期属性 , 如果成功 , 就说明验证成功了 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">验证全局消息转发页面可行性 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> a. 在上面的servlet/WebUtilsTest中调用forward()方法 ,传入request , response , “验证全局消息页面” , 如果最后提交完表单后 , 自动跳转到这个页面 , 说明验证成功</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2)JdbcUtils</span><span style="font-family:黑体; word-wrap:break-word">工具类</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:red; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">从配置文件中获取</span></span><span style="color:red; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">jdbc</span></span><span style="color:red; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">四要素步骤</span></span><span style="color:red; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> :</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 设置静态代码块 , 在该类加载的时候就获取四要素 , 只获取依次就可以 , 以后就没必要调用了 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 创建Properties类的对象 , 用来接受配置文件中的数据 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 使用 JdbcUtils.class.getClassLoader.getResourceAsStream(“”)方法将配置文件传入输入流中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 关联Properties对象和输入流</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 从Properties对象中取数据 , 并进行操作 , 加载驱动也是在这一步完成的 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:red; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:10.5pt">释放资源方法</span></span></span> :</span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 一个if语句是一组 , 一共yao释放三个对象 , 这三个方法都是差不多的 , 只是变量不同 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 在每个if语句中 , 先判断变量是否为空 , 如果不为空就关闭 , 然后为了以防万一在将其指向null .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:red; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="word-wrap:break-word; font-size:10.5pt">导包问题</span></span></span> :</span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 注意 , 这个方法中的 Connection , PreparedStatement , ResultSet 类导入的包均为java.sql包下的 , 不是mysql下的 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">a. </span><span style="font-family:宋体; word-wrap:break-word">先私有化构造函数</span><span style="font-family:Times New Roman; word-wrap:break-word"> , </span><span style="font-family:宋体; word-wrap:break-word">工具类不允许创建对象</span><span style="font-family:Times New Roman; word-wrap:break-word"> .</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">private JdbcUtils(){}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">b. </span><span style="font-family:宋体; word-wrap:break-word">设置全局变量</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">将数据库路径 uri , 账号 uer , 密码 password 设置为类的全局变量 . 因为这些变量是在静态代码块中读取到的 , 然后在下面的数据库连接方法中还要使用 , 因此要设置为全局变量 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">static{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">c. </span><span style="font-family:宋体; word-wrap:break-word">设置静态代码块</span><span style="font-family:Times New Roman; word-wrap:break-word"> , </span><span style="font-family:宋体; word-wrap:break-word">处理四要素</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">设置一个静态代码块 , 在静态代码块中读取配置文件 , 注册驱动 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">Properties</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span>类表示了一个持久的属性集。<span style="font-family:宋体; word-wrap:break-word">Properties</span><span style="font-family:Times New Roman; word-wrap:break-word"> </span>可保存在流中或从流中加载。属性列表中每个键及其对应值都是一个字符串。</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> static{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //读取配置问文件 , 获取四要素</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Properties props = new Properties(); //创建一个Properties对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //将jdbc.Properties文件读取到输入流中</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> InputStream in = JdbcUtils.class.getClassLoader().getRespurceAsStream(“jdbc.Properties”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //相当于将文件与props对象关联 , 将文件中的键值对存到props对象中</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">props.load(in);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">//取出驱动名字 , 加载驱动</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">String driverClassName = props.getProperty(“DriverClass”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">Class.classForName(driverClassName);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">//取出数据库路径</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">uri = props.getProperty(“uri”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">//取出数据库的用户名</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">user = props.getProperty(“user”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">//取出数据库密码</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">password = props.getProperty(“password”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> throw new</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">d.</span><span style="font-family:宋体; word-wrap:break-word">创建连接方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"></span>注意这里的<span style="font-family:Times New Roman; word-wrap:break-word">Connection</span>需要导入的包是<span style="font-family:Times New Roman; word-wrap:break-word"> java.sql.Connection .</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public static Connection getConnection() throws SQLException{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return DriverManger.getConnection(uri , user , password);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">e.</span><span style="font-family:宋体; word-wrap:break-word">释放资源方法</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public static void release(Connecttion conn , Statement stmt , ResultSet rs){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(conn != null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn.close();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.printStackTrace ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(stmt != null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt.close();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.printStackTrace ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">stmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(rs!= null){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs.close();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.printStackTrace ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> }</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(4)</span><span style="font-family:宋体; word-wrap:break-word">实现</span><span style="font-family:Times New Roman; word-wrap:break-word">Dao</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1)</span><span style="font-family:黑体; word-wrap:break-word">获得所有的员工</span></span></span><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">流程介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象放到方法的全局变量中 , 并赋值null , 这是因为在try finally两个区域都要用到这些对象 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得连接 , 调用 JdbcUtils.getConnection()来获得 , 得到conn对象;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用conn.PreparedStatement(sql语句字符串)方法获得 stmt对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 发送sql语句 , 调用stmt.executeQuery()方法 , 得到rs对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 处理rs对象中的数据 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">异常处理</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在Dao中出现的异常 , 我们都将其抓起来 , 然后转为一个运行时异常抛出 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 先写一个异常 ,然后会报错 , 我们就ctrl+1 处理错误 , 创建这个异常 , 然后就将异常制定创建在Exception包中 , 继承RuntimeException , 并且继承所有的方法 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public List getAll(){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //由于有try catch 语句 , 这些变量除了在try中使用以外 , 还要在finally中使用 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement stmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection(); //获得连接</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //预编译sql语句</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “select * from employees” ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //发送sql语句</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs = stmt.executeQuery();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //处理结果集 , 我们将取出的数据封装在employee对象中 , 将employee对象都放在list中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> List list = new ArrayList();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //遍历rs</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> while(rs.next()){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee e = new Employee(); //创建一个employee对象 , 用来封装结果</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setBirthday(rs.getDate(“birthday”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setEntryDate(rs.getDate(“entrydate”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setdegree(rs.getString(“degree”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setDepartment(rs.getString(“department”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setGender(rs.getString(“gender”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setId(rs.getString(“id”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setIdcard(rs.getString(“idcard”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setName(rs.getString(“name”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setPosition(rs.getString(“position”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> list.add(e); //将封装好的对象加入到list中</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">return list; //将list返回</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release(conn , stmt , rs);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2)</span><span style="font-family:黑体; word-wrap:break-word">根据</span><span style="font-family:Arial; word-wrap:break-word">id</span><span style="font-family:黑体; word-wrap:break-word">查找</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">流程介绍</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象设置为方法的全局变量 , 因为在try 和 finally区域中要使用这些变量 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得连接 , 调用JdbcUtils.getConnection()方法 , 得到Connecttion对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用conn.preparedStatement(sql语句)方法 , 预编译sql语句 , 得到PreparedStatement对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 发送sql语句 , 调用 stmt.executeQuery()方法 , 执行sql语句 , 返回ResultSet对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 处理结果集 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public Employee find(String id){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement stmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection(); //获得连接</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //预编译sql语句</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “select * from employees where id=?” ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //替换占位符</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt.setString(1,id);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //发送sql语句</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs = stmt.executeQuery();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //遍历rs</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> while(rs.next()){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee e = new Employee(); //创建一个employee对象 , 用来封装结果</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setBirthday(rs.getDate(“birthday”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setEntryDate(rs.getDate(“entrydate”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setdegree(rs.getString(“degree”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setDepartment(rs.getString(“department”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setGender(rs.getString(“gender”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setId(rs.getString(“id”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setIdcard(rs.getString(“idcard”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setName(rs.getString(“name”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setPosition(rs.getString(“position”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return e ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">return null; //将list返回</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release(conn , stmt , rs);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">3)</span><span style="font-family:黑体; word-wrap:break-word">添加</span><span style="font-family:Arial; word-wrap:break-word">employee</span><span style="font-family:黑体; word-wrap:break-word">对象到数据库</span></span></span><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">流程介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象设置为方法的全局变量 , 因为在try 和 finally 两个区域都用到了这三个对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得连接 , 调用 JdbcUtils.getConnection()方法 , 得到conn ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用conn.PreparedStatement(sql语句)方法 ,得到PreparedStatement对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 替换占位符</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 发送sql语句 , 调用stmt.executeUpdate()方法 , 得到一个int型数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">关于替换占位符</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 先进行预编译 , 先执行conn.preparedStatement(sql)方法 , 将sql语句与pstmt关联起来 , 我们才能使用PreparedStatement类下的替换占位符方法 ,</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">如果是字符串形式 , 我们可以使用setString(1 , “张三”) , 如果是日期形式 , 我们可以使用 setDate(1 , java.sql.Date对象) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 替换占位符的方法一般是 : set被替换的类型(占位符的索引 , 被替换的实体) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 如果被替换的是字符串 ,那么被替换的类型就是String , 方法就是 setString() ; 如果被替换的是日期 , 被替换的类型就是Date类型 , 不过这个Date是java.sql.Date , 一定要区分java.utils.Date , 方法就是setDate() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 关于替换Date的处理 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们使用setDate(index , new java.sql.Date(dateStamp)); 新建一个sql的Date对象 , 在构造函数中传入一个时间戳 , 时间戳就是从1970年到现在的毫秒数 ,在本程序中 , 我们是这样处理的 , 先取出utils的Date , 然后获得时间戳 , 再将时间戳传入sql的Date构造函数 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> setDate(index , new java.sql.Date(bean.getDate().getTime()));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public boolean save(employee bean){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement pstmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获得连接 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//预编译sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “insert into employees (id,name,gender,birthday,idcard,degree,entrydate,department,position) values(?,?,?,?,?,?,?,?,?)”</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//替换占位符 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.preparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(1 , bean.getId());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(2 , bean.getName());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(3 ,bean.getGenter());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setDate(4 , new java.sql.Date(bean.getDate().getTime()));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(5 , bean.getIdcard());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(6 , bean.getDegree());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setDate(7 , new java.sql.Date(bean.getEntrydate().getTime()));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(8 , bean.getDepartment());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(9 , bean.getPosition());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//发送sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int num = stmt.executeUpdate();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(num > 0)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return true ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return false;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">4)</span><span style="font-family:黑体; word-wrap:break-word">修改数据库中的</span><span style="font-family:Arial; word-wrap:break-word">employee</span><span style="font-family:黑体; word-wrap:break-word">数据</span></span></span><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">流程介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet ,三个类的对象 conn , pstmt , rs的声明提为该方法的全局变量 , 因为在try和finally两个区域中都要用到这三个对象 , 在try中是对数据库操作的需要 , 在finally中是在释放资源的时候 , 将这三个对象全部释放 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得数据库连接 , 调用JdbcUtils.getConnection()方法 , 获得conn对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用conn.PreparedStatement(sql)方法 , 获得PreparedStatement对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 替换占位符</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 发送sql语句 , 返回是否成功修改得到一个布尔值 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public boolean update(employee bean){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement pstmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获得连接 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//预编译sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “update employees set name , gender=? , birthday=? , idcard=? , degree=? , entrydate=? , department =?, position where id =?”;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//替换占位符 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.preparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(1 , bean.getName());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(2 ,bean.getGenter());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setDate(3 , new java.sql.Date(bean.getDate().getTime()));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(4 , bean.getIdcard());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(5 , bean.getDegree());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setDate(6 , new java.sql.Date(bean.getEntrydate().getTime()));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(7 , bean.getDepartment());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(8 , bean.getPosition());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(9 , bean.getId());</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//发送sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int num = stmt.executeUpdate();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(num > 0)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return true ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return false;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">5)</span><span style="font-family:黑体; word-wrap:break-word">删除一个员工</span></span></span><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">流程介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象设置为方法的全局变量</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得数据库连接 , 调用JdbcUtils.getConnection()方法 , 获得conn ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql , conn.PreparedStatement(sql) , 得到pstmt对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 替换占位符</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 发送sql语句 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public boolean update(int id){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement pstmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获得连接 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//预编译sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “delete from employees where id =?”;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//替换占位符 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.preparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt.setString(1 , id);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//发送sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int num = stmt.executeUpdate();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(num > 0)</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return true ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return false;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">6)</span><span style="font-family:黑体; word-wrap:break-word">查询记录数</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">流程介绍</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象设置为方法的全局变量 , 在try中需要这3个变量进行数据库操作 , 在finally中需要将这三个变量释放掉 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 得到数据库连接 , 调用JdbcUtils.getConnection()方法 , 得到conn对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用 conn.PreparedStatement(sql)方法 , 得到 pstmt对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 发送sql语句 , 调用pstmt.executeQuery()方法 , 得到rs对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 处理结果集</span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">注意</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">凡是查询返回的都是rs对象 , 增删改返回的都是int对象 .</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> 获得查询的数据 , 以dos窗口中的列名为准 , 例如这次查询 count(*) , 我们最后从rs中获取的时候也是用</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word">rs.getString(“count(*)”)方法 .</span></span> </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> </span></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">代码</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public int getotalRecord(){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement pstmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//获得连接 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//预编译sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “select count(*) from employees”;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> pstmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//发送sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs = stmt.executeQuery();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //处理结果集</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(rs.next()){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return getInt(“count(*)”);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">return 0;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">7)</span><span style="font-family:黑体; word-wrap:break-word">查询分页显示数据</span></span></span><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">流程介绍</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 将Connecttion , PreparedStatement , ResultSet 对象设置为方法的全局变量 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 获得连接 , 调用JdbcUtils.getConnection()方法 , 得到conn对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 预编译sql语句 , 调用conn.PreparedStatement(sql)方法 ,得到pstmt对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 发送sql语句 , 调用 pstmt.executeQuery()方法 ,得到rs对象 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 处理结果集 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public List getPageData(int start , int len){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//由于有try catch 语句 , 这些变量除了在try中使用以外 , 还要在finally中使用 . </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Connecttion conn = null;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> PreparedStatement stmt = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> ResultSet rs = null ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> try{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> conn = JdbcUtils.getConnection(); //获得连接</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//预编译sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> String sql = “select * from employees limite ?,?” ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt = conn.PreparedStatement(sql);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//替换占位符 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt.setInt(1, start);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> stmt.setInt(2, len);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//发送sql语句 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> rs = stmt.executeQuery();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//处理结果集 , 我们将取出的数据封装在employee对象中 , 将employee对象都放在list中 . </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> List list = new ArrayList();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//遍历rs </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> while(rs.next()){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee e = new Employee(); </span>//创建一个employee对象 , 用来封装结果 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setBirthday(rs.getDate(“birthday”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setEntryDate(rs.getDate(“entrydate”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setdegree(rs.getString(“degree”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setDepartment(rs.getString(“department”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setGender(rs.getString(“gender”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setId(rs.getString(“id”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setIdcard(rs.getString(“idcard”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setName(rs.getString(“name”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> e.setPosition(rs.getString(“position”));</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> list.add(e); </span>//将封装好的对象加入到list中 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">return list; </span>//将list返回 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}catch(Exception e){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> throw</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}finally{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> JdbcUtils.release(conn , stmt , rs);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">8)</span><span style="font-family:黑体; word-wrap:break-word">验证是否可用</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> a. </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">findAll()</span><span style="font-family:宋体; word-wrap:break-word">和</span><span style="font-family:Times New Roman; word-wrap:break-word">JdbcUtils()</span><span style="font-family:宋体; word-wrap:break-word">方法</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> 第一种方法</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 在首页中链接到servlet/UiWebUitlsTest页面中去 , 我们在这个页面测试这个方法 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 在servlet/UiWebUitlsTest中调用JdbcUtils.findAll()方法 , 将返回的list打印出来 , 这种方法不好 , 验证起来很麻烦 , 我们只需要看看getAll()方法能不能将数据全部取出 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word">第二种方法(推荐)</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">我们创建一个主函数类Test类 , 在主函数中调用getAll()方法 , 这样有很明显的提示 , 在这里出现了两个错误 , 第一个是将jdbc.properties配置文件中的url写错了 , 写成uri , 在这里注意 , 另外将sql语句中的表名写错了 , 改完这两个错误 , 成功将方法返回的list打印出来 , 并且能在list中查看相关的变量 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> b. </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">getById()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在Test中输入下面的代码 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee bean = </span> <span style="word-wrap:break-word">dao</span>.getById("1"); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println("test--> getById() : " + bean); </div> <div style="word-wrap:break-word"> 执行 , 如果能打印出取出的代码 , 就说明该方法可行 </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> c. </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">insert()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在Test中输入以下代码 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee bean2 = </span> <span style="word-wrap:break-word">new</span> Employee(); </div> <div style="word-wrap:break-word"> bean2.setId("2"); </div> <div style="word-wrap:break-word"> bean2. <span style="word-wrap:break-word">setBirthday</span>( <span style="word-wrap:break-word">new</span> Date()); </div> <div style="word-wrap:break-word"> bean2.setEntrydate( <span style="word-wrap:break-word">new</span> Date()); </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">boolean</span> b = <span style="word-wrap:break-word">dao</span>.insert(bean2); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println("test--> insert() : " + b); </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这里只有id是必须的 , 不过在这里必须写上日期 , 我们在替换占位符的时候 , 使用的 new java.sql.Date(bean.getBirtiday().getTime())方法 , 如果我们不输入日期 , 那么就会出现空指针调用 , 抛出空指针异常 , 因此我们将两个日期加上去 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个方法我们不用的时候 , 将其注释掉 , 因为这个每次执行都要修改以下传入的参数 , 我们插入了id为1 ,下一次就不能再插入1 了 , 因为id是主键, 如果插入逐渐重复就会出现异常 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> d. </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">update()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> </span></span>//测试EmployeeDao类中的update()方法是否可用 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Employee bean3 = </span> <span style="word-wrap:break-word">new</span> Employee(); </div> <div style="word-wrap:break-word"> bean3.setId("000fb8a5-7d13-460f-9ffb-f17cd8aa59b6"); </div> <div style="word-wrap:break-word"> bean3.setBirthday( <span style="word-wrap:break-word">new</span> Date()); </div> <div style="word-wrap:break-word"> bean3.setEntrydate( <span style="word-wrap:break-word">new</span> Date()); </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">boolean</span> b1 = <span style="word-wrap:break-word">dao</span>.update(bean3); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println("test--> update() : " + b1); </div> <div style="word-wrap:break-word"> 使用上面的方法来验证是否更新成功 . </div> <span style="word-wrap:break-word"><span style="color:black; word-wrap:break-word"><span style="word-wrap:break-word; font-size:10pt"><span style="font-family:Times New Roman; word-wrap:break-word"> e. </span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">delete()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//测试EmployeeDao类中的delete()方法是否可用 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">boolean</span> b2 = <span style="word-wrap:break-word">dao</span>.delete("2"); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println("test--> delete() : " + b2); </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word"> f.</span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">getTotalRecord()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//测试EmployeeDao类中的getTotalRecord()方法是否可用 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">int</span> totalRecord = <span style="word-wrap:break-word">dao</span>.getTotalRecord(); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println(totalRecord); </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"> g.<span style="font-family:Times New Roman; word-wrap:break-word"> </span><span style="font-family:宋体; word-wrap:break-word">验证</span><span style="font-family:Times New Roman; word-wrap:break-word">getPageData()</span><span style="font-family:宋体; word-wrap:break-word">方法是否可用</span></span></span></span> <div style="word-wrap:break-word"> //测试EmployeeDao类中的getPageData()方法是否可用 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">List</span> pageData = <span style="word-wrap:break-word">dao</span>.getPageData(1, 5); </div> <div style="word-wrap:break-word"> System. <span style="word-wrap:break-word">out</span>.println(pageData); </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(5)</span><span style="font-family:宋体; word-wrap:break-word">实现</span><span style="font-family:Times New Roman; word-wrap:break-word">service</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> service是业务逻辑层 , 这层代码起着承上启下的作用 , web层调用service , service调用dao层的方法和成员 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在service中 , 代码很简单 ,我们只需要创建一个私有的EmployeeDao成员变量 , 通过这个私有的对象调用EmployeeDao中的方法 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 代码 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public class service{</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//创建一个EmployeeDao实体类 , 我们通过这个实体类调用EmployeeDao中操作数据库的方法 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> private EmployeeDao dao = new EmployeeDao();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span>//得到所有员工信息 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public List getAll(){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return dao.getAll();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> //根据id查找员工信息 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public Employee getById(String id){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return dao.getById(id) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> //插入员工信息 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public boolean insert(Employee bean){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return dao.insert(bean);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> //修改员工信息 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public boolean update(Employee bean){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return dao.update(bean);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> //删除员工信息 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">public boolean delete(String id){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> return dao.delete(id);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(6)</span><span style="font-family:宋体; word-wrap:break-word">几个页面链接</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 我们使用浏览器首先登陆的是首页 , 我们通过首页跳转到UiServlet , 在通过UiServlet跳转到其它页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 首页中所有的跳转都是跳转向UiServlet中 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 在index.jsp首页中设置两个链接 , 分别连接到查看所有的员工页 , 和添加员工页 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">首页中的代码</span> :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <a href = “${pageContext.request.contextPath}/servlet/UiGetAllServlet”>查看所有的员工 </a></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <a href = “${pageContext.request.contextPath}/servlet/UiAddServlet”>添加员工 </a></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 通过上面的链接能到相关的UiServlet页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">UiGetAllServlet页面代码</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个页面中我们调用service中的getAll()方法 , 将获得的List对象存入request中 . 跳转代码如下 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> request.getRequestDispather(“/WEB-INF/pages/getalldata.jsp”).forward(request , response);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 通过执行上面的语句 , 可以直接跳转到查看所有员工页面 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> <span style="word-wrap:break-word">UiAddServlet页面代码</span></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这个是一个纯跳转页面 , 只实现跳转功能 . 代码如下 :</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> request.getRequestDispather(“/WEB-INF/pages/add.jsp”).forward(request , response);</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"><span style="word-wrap:break-word"> 页面连接做完之后 ,我们就能够登陆首页 , 进行相应的页面跳转了 .</span></span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Times New Roman; word-wrap:break-word">(7) </span><span style="font-family:宋体; word-wrap:break-word">分页实现</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">1)</span><span style="font-family:黑体; word-wrap:break-word">分页需求</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">由于数据库中的数据量过大 , 在一个页面显示所有的数据用户体验不够好 , 因此我们使用了分页 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 实现上图所示的需求 , 我们来逐条分析 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 除了上面的图片之外 , 我们还需要有显示的数据 , 这里每页显示10条信息 , 显示的数据都放在一个List中 , 显然我们需要一个List变量 , pageData来存放要显示的数据 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 显示当前的页数 , 当前第几页 , 我们根据页数来从数据库中查询相关信息 , 这个用一个String变量pageNum来表示 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 总记录数 , 我们使用count(*)可以得到 , String totalRecord ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 总页数 , 总记录数除以每页显示的数据条数count , 注意这里的算法 totalPageNum = ( totalRecord + (count - 1) )/count ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 起始页码 , 总共显示10页的编号 , 一般来说 , 起始页码就是当前页减去5 , 如果当前页小于5 , 那就显示1-10 编号 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">f. 终止页码 , 当前页加上4 , 如果当前页是大于totalPageNum-4 , 那么就显示 totalPageNum-9 – totalPageNum编号 ;</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">2)</span><span style="font-family:黑体; word-wrap:break-word">创建</span><span style="font-family:Arial; word-wrap:break-word">page</span><span style="font-family:黑体; word-wrap:break-word">实体类</span><span style="font-family:Arial; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> </span> <span style="word-wrap:break-word">private</span> <span style="word-wrap:break-word">List</span> pageData; // 分页显示的数据 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> pageNum; // 当前页码 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> totalRecord; // 总记录数 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> totalPageNum; // 总页数 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> firstPageNum; // 起始页码 </div> <div style="word-wrap:break-word"> <span style="word-wrap:break-word">private int</span> lastPageNum; // 结束页码 </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 获得其getter和setter方法 .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:Arial; word-wrap:break-word">3)</span><span style="font-family:黑体; word-wrap:break-word">分页</span><span style="font-family:Arial; word-wrap:break-word">service</span><span style="font-family:黑体; word-wrap:break-word">实现</span></span></span><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">底层</span><span style="font-family:Times New Roman; word-wrap:break-word">dao</span><span style="font-family:宋体; word-wrap:break-word">实现</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">分页的底层是基于EmployeeDao的getTotaoRecord()方法和getPageDate()方法实现的 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 其中getTotaoRecord()方法是获得数据库中该表的总记录数 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> getPageDate()方法是获得从一个起始位置 , 制定长度的记录数 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"></span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> 这里主要解析service实现 , 分页的service主要是封装page .</span> </div> <span style="word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word">流程介绍</span><span style="font-family:Times New Roman; word-wrap:break-word"></span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">a. 创建Page对象 , 这个对象是要返回的 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">b. 设置count , 这个很重要 , 表示每页显示数据条数 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">c. 查询总记录数 , 创建一个EmployeeDao对象 , 通过这个对象调用getTotaoRecord()方法 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">d. 计算总页数 , 使用 ( TotalRecord + ( count - 1 ) ) / count 方法 .</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">e. 查询分页显示的数据 , 开始位置是 ( PageNum – 1 ) * count , 长度为count ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">f. 计算起始页码和结束页码 , 起始页码为当前页-5 , 终止页码为当前页+4 , 如果当前页是前5页 , 那么显示前10页页码 , 如果当前页是后4页 , 那么显示后10页页码 , 如果页面不足10页 , 那就第一页是当前页 , 最后一页是终止页 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">g. PageNum是通过参数传递进来的 , 将上面的所有的数据封装起来返回 .</span> </div> <span style="word-wrap:break-word"><span style="font-family:宋体; word-wrap:break-word"><span style="font-size:24px; word-wrap:break-word"><span style="color:#000000; word-wrap:break-word">代码</span></span></span></span> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> public Page getPage( int pageNum ){</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //创建Page对象</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> Page page = new Page();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //设置count</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int count = 10 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //创建EmployeeDao对象 , 使用该对象操作数据库</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> EmployeeDao dao = new EmployeeDao() ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //查询总记录数</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int totalRecord = dao.getTotaoRecord();</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //计算总页数</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int totalPageNum = ( totalPageNum + ( count - 1 ) ) / count ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //查询分页显示数据</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int start = ( pageNum – 1 ) * 10 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int len = count ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> List list = getPageDate( start , len ) ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //计算页码显示起始页和终止页</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int firstPage = pageNum - 5 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> int lastPage = pageNum + 4 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> //将三种特殊情况筛选出来</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> if(firstPage < 1){ //这种情况是当前页是前5页的情况</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> firstPage = 1 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> lastPage = 10 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">if(lastPage > pageNum){ //这种情况是当前页是后四页的情况</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> firstPage = totalPageNum -9 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> lastPage = totalPageNum ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">}</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word">if(totalPageNum < 10){ //这种情况是总页数不足10页的情况</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> firstPage = 1 ;</span> </div> <div style="word-wrap:break-word"> <span style="color:#000000; word-wrap:break-word"> lastPage = totalPageNum ;</span> 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