javaee学习之路(十四)JSP编程实例
例1、输出当前时间值。
1.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>jsp入门案例（输出时间）</title>
</head>
<body>
当前时间值是：
<% Date date=new Date(); out.write(date.toLocaleString()); %>
</body>
</html>找到tomcat服务器当中对应的Servlet文件C:\tomcat\work\Catalina\localhost\day08\org\apache\jsp\ _1_jsp.java
……
out.write("\r\n");
out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
out.write("<html>\r\n");
out.write(" <head>\r\n");
out.write(" <title>jsp入门案例（输出时间）</title> \r\n");
out.write("</head>\r\n");
out.write("<body>\r\n");
out.write("当前时间值是：\r\n");
out.write(" ");
Date date=new Date();
out.write(date.toLocaleString());
out.write("\r\n");
out.write(" </body>\r\n");
out.write("</html>\r\n");<% %>之间的内容被原封不动地嵌套在了servlet当中
例2、Page指令之errorPage，怎样处理JSP当中的异常—实际开发当中案例1。
Step1、1.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>jsp入门案例（输出时间）</title>
</head>
<body>
<% int x=1/0; out.print(x); %>
</body>
</html>Step2、web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<error-page>
<exception-type>java.lang.ArithmeticException</exception-type>
<location>/errors/error.jsp</location>
</error-page>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>Step3、error.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'error.jsp' starting page</title>
</head>
<body>
对不起，出错了！！！ <br>
</body>
</html>例3、Page指令之errorPage，怎样处理JSP当中的异常—实际开发当中案例1
Step1、
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<error-page>
<exception-type>java.lang.ArithmeticException</exception-type>
<location>/errors/error.jsp</location>
</error-page>
<error-page>
<error-code>404</error-code>
<location>/errors/404.jsp</location>
</error-page>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>Step2、404.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP '404.jsp' starting page</title>
</head>
<body>
对不起，您访问的资源不存在！！！ <br>
</body>
</html>Step3、在IE中键入htpp://localhost:8080/day08/fandong
例3、JSP乱码问题。
在Eclipse当中只需要这只PageEncoding就行了
例4、include指令实例代码
Step1、在WebRoot目录之下建立目录public,在其中放入head.jsp和foot.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>head.jsp</title>
</head>
<body>
这是页头！！！ <br>
</body>
</html><%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>foot.jsp</title>
</head>
<body>
这是页脚！！！ <br>
</body>
</html>Step2、在WebRoot目录下创建页面2.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>include指令(静态包涵)</title>
</head>
<body>
<%@include file="/public/head.jsp"%>
aaaa<br>
<%@include file="/public/foot.jsp"%>
</body>
</html>Step3、在ie中键入: http://localhost:8080/day08/2.jsp可得
这是页头！！！
aaaa
这是页脚！！！1、 在实际开发当中通常将head.jsp和foot.jsp等被包涵的文件写为一下格式:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
这是页头！！！<br> (即只留下声明和与当中的内容即可)
2、include指令（静态包涵，编译时包含，被包涵的JSP文件与包涵的Jsp文件一起编译成一个servlet）
3、动态包涵：3.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>动态包涵(这种情况是运行时包含)</title>
</head>
<body>
<% request.getRequestDispatcher("/public/head.jsp").include(request,response); %>
<% response.getWriter().write("aaaaaaaaaaa <br>"); %>
<% request.getRequestDispatcher("/public/foot.jsp").include(request,response); %>
</body>
</html>在实际开发当中尽量用静态包含！！！！！
例5、out隐式对象
问题演示：4.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP '4.jsp' starting page</title>
</head>
<body>
Aaaaaaa//编译之后用out输出
<% out.write("hahahahahha"); response.getWriter().write("wuuwuwuwuuwu"); %>
</body>
</html>在IE中键入:http://localhost:8080/day08/4.jsp可以看到：
wuuwuwuwuuwu aaaaaaaa hahahahahha
问题在于并没有出想ha在前wu在后的情况,原因:out有缓存
例6、PageContext对象访问其他域对象(4.jsp)
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>pageContext对象访问其他域</title>
</head>
<body>
<% request.setAttribute("data","fandong"); String data=(String)pageContext.getAttribute("data",PageContext.REQUEST_SCOPE); out.write(data); %>
</body>
</html>在IE中可以得到:fandong
例7、pageContext域对象之findAttribute方法之应用。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>pageContext对象访问其他域</title>
</head>
<body>
<% request.setAttribute("data","fandong"); String data=(String)pageContext.getAttribute("data",PageContext.REQUEST_SCOPE); out.write(data+"<br/>"); String data2=(String)pageContext.findAttribute("data"); out.write(data2); %>
</body>
</html>在IE中可以得到:fandong
fandong
例8、标签的作用
Step1、5.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>JSP常用标签</title>
</head>
<body>
<% String x="12"; %>
<jsp:forward page="/servlet/ServletDemo1">
<jsp:param value="<%= x %>" name="password"/>
<jsp:param value="fandong" name="username"/>
</jsp:forward>
</body>
</html>Step2、ServletDemo1.java
package cn.itcast.web.servlet;
import *;
public class ServletDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String username=request.getParameter("username");
System.out.println(username);
String x = (String)request.getParameter("password");
System.out.println(x);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}Step3、在IE中键入：htpp://localhost:8080/day08/5.jsp可以看到：fandong 12
例9、应用实例之一。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>jsp:usebean</title>
</head>
<body>
<%--创建一个Person对象,这个对象的名字叫做person,(如果在page域中有了一个Person就直接拿过来用，不另外创建)--%>
<%-- useBean标签的标签提只在useBean标签实例化bean时才执行--%>
<jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page">
Fandong!!!!
</jsp:useBean>
<%=person.getName() %>
</body>
</html> 上面的过程中，当浏览器第一次访问1.jsp时，useBean标签会实例化Person对象，此时标签之间的Fandong!!!!会执行下去，会在浏览其中显示，但是，当第二次访问1.jsp时就不会执行了，因为已经在page域当中创建了persion的对象了！
例10、2.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>jsp:setProperty标签</title>
</head>
<body>
<jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"/>
<%--手工为bean赋值 --%>
<jsp:setProperty name="person" property="name" value="xxx"/>
<%--赋当前时间值给属性birthday --%>
<jsp:setProperty name="person" property="birthday" value="<%=new Date()%>"/>
<%=person.getName() %><br/>
<%=person.getBirthday() %><br/>
<%--用请求参数给bean的属性赋值 --%>
<jsp:setProperty property="name" name="person" param="name"/>
<jsp:setProperty property="age" name="person" param="age"/>
<%=person.getName() %><br/>
<%=person.getAge() %><br/>
</body>
</html> 在IE中键入http://localhost:8080/day09/2.jsp?name=fandong&age=12可以得到结果:
xxx
Sat Sep 15 17:52:51 CST 2012
fandong
12
例11、为所有参数赋值。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>jsp:setProperty标签</title>
</head>
<body>
<jsp:useBean id="person" class="cn.itcast.domain.Person" scope="page"/>
<%--用所有的请求参数为bean赋值 --%>
<jsp:setProperty property="*" name="person"/>
<%=person.getName()%>
上面这一句代码等同于<jsp:getProperty name=”person” ptoperty=”name”/>
<%=person.getAge()%>
</body>
</html> 在IE中键入http://localhost:8080/day09/2.jsp?name=fandong&age=12可以得到结果:
fandong
12
（注意IE栏中带过来的参数名称应该与bean中的属性名一样）
说明：在servlet当中自动将”12”转为了整形。这个标签支持8中数据类型的转换（把客户机提交的字符串转为8中基本数据类型赋值到jean当中）。
例13、使用Jsp+javabean编写一个计算器页面，javaBean具有firstNum、secondNum、result、operator属性，并提供一个calculate方法.
补充:实现各种数的精确运算：
package cn.itcast.domain;
import java.math.BigDecimal;
public class Demo1 {
public static void main(String[] args){
BigDecimal a=new BigDecimal("0.1");
BigDecimal b=new BigDecimal("0.006");
BigDecimal c=new BigDecimal("0.3");
System.out.println(a.add(b).toString());
System.out.println(a.multiply(b).toString());
System.out.println(a.divide(c, 10,BigDecimal.ROUND_HALF_UP));
//表示保留小数点后面10位
}
}输出结果为:
0.106
0.0006
0.3333333333
Step1、calculator.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>计算器</title>
</head>
<body style="text-align: center">
<jsp:useBean id="calculatorBean" class="cn.itcast.domain.CalculatorBean"></jsp:useBean>
<jsp:setProperty property="*" name="calculatorBean"/>
<% try{ calculatorBean.calculator(); }catch(Exception e) { out.write(e.getMessage());//把异常给用户友好提示 } %>
<br/>--------------------------------------------------------<br/>
计算结果是:
<jsp:getProperty property="firstNum" name="calculatorBean"/>
<jsp:getProperty property="operator" name="calculatorBean"/>
<jsp:getProperty property="secondNum" name="calculatorBean"/>
=
<jsp:getProperty property="result" name="calculatorBean"/>
<br/>--------------------------------------------------------<br/>
<form action="/day09/calculator.jsp" method="post">
<table width="40%" border="1">
<tr>
<td colspan="2">简单的计算器</td>
</tr>
<tr>
<td>第一个参数</td>
<td>
<input type="text" name="firstNum"/>
</td>
</tr>
<tr>
<td>运算符</td>
<td>
<select name="operator">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
</td>
</tr>
<tr>
<td>第二个参数</td>
<td><input type="text" name="secondNum"/> </td>
</tr>
<tr>
<td colspan="2">
<input type="submit" value="计算"/>
</td>
</tr>
</table>
</form>
</body>
</html>Step2、CalculatorBean.java
package cn.itcast.domain;
import java.math.BigDecimal;
//封转计算器数据的bean
public class CalculatorBean {
private String firstNum="0";
private String secondNum="0";
private char operator='+';
private String result;
public String getFirstNum() {
return firstNum;
}
public void setFirstNum(String firstNum) {
this.firstNum = firstNum;
}
public String getSecondNum() {
return secondNum;
}
public void setSecondNum(String secondNum) {
this.secondNum = secondNum;
}
public char getOperator() {
return operator;
}
public void setOperator(char operator) {
this.operator = operator;
}
public String getResult() {
return result;
}
public void setResult(String result) {
this.result = result;
}
public void calculator(){
BigDecimal first=new BigDecimal(this.firstNum);
BigDecimal second=new BigDecimal(this.secondNum);
switch (this.operator) {
case '+':{
this.result=first.add(second).toString();
break;}
case '-':{
this.result=first.subtract(second).toString();
break;}
case '*':{
this.result=first.multiply(second).toString();
break;}
case '/':{
if(second.doubleValue()==0){
throw new RuntimeException("被除数不能为0");
}
this.result=first.divide(second,10,BigDecimal.ROUND_HALF_UP).toString();
break;}
default:{
throw new RuntimeException("运算符错误!");
}
}
}
}
例14、EL表达式例程。（3.jsp）
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>EL表达式例程</title>
</head>
<body>
<% String data="fandong"; request.setAttribute("data",data); %>
${data}<%--相当于pageContext.findAttribute(“data”);--%>
</body>
</html>在IE中键入:http:localhost:8080/day09/3.jsp便可以看到：
fandong
例15、EL表达式快速入门。
Step1、Person.java
package cn.itcast.domain;
import java.util.Date;
public class Person {
private String name;
private Address address;
public Person() {
super();
}
public Person(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}Step2、Address.java
package cn.itcast.domain;
public class Address {
private String city;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
}Step3、3.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%%@page import="cn.itcast.domain.Person"%%>
<%@page import="cn.itcast.domain.Address"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>EL表达式例程</title>
</head>
<body>
<% String data="fandong"; request.setAttribute("data",data); %>
${data}<%--相当于pageContext.findAttribute(“data”);--%>
<br>
<% Person p=new Person(); p.setName("denghongmei!"); request.setAttribute("person",p); %>
${person.name}
<br>
<% Person p1=new Person(); Address a=new Address(); a.setCity("上海"); p1.setAddress(a); request.setAttribute("p1",p1); %>
${p1.address.city}
<br>
<%-- p1上面的request设置的属性名称，而后面的为bean封装的属性--%>
<%--EL表达式读取集合当中的内容--%>
<% List list=new ArrayList(); list.add(new Person("aaa")); list.add(new Person("bbb")); list.add(new Person("ccc")); request.setAttribute("list",list); %>
${list[0].name}
<br>
<% Map map=new HashMap(); map.put("aa",new Person("aaaa")); map.put("bb",new Person("bbbb")); map.put("cc",new Person("cccc")); map.put("dd",new Person("dddd")); map.put("1111",new Person("eeee")); request.setAttribute("map123",map); %>
${map123.bb.name}
<br>
<%--用${map123.1111.name}取不出来数据的,这是要用[]来取 --%>
${map123['1111'].name}
<br>
<%--得到当前web应用的名称,用在超链接等地方 --%>
${pageContext.request.contextPath}
<br>
<a href="${pageContext.request.contextPath}/index.jsp">点击</a>
</body>
</html>例16、使用jstl和EL完成集合的迭代。
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@page import="cn.itcast.domain.Person"%>
<%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<%--上面一行的作用是导入标签库,上面的uri怎么来的? 在eclipse左侧目录点击day09项目->Reference Libraries->standard.jar->META-INF->c.tld->找到映射的<uri>http://java.sun.com/jsp/jstl/core</uri>--%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>使用jstl+EL完成集合迭代</title>
</head>
<body>
<% List list=new ArrayList(); list.add(new Person("aaa")); list.add(new Person("bbb")); list.add(new Person("ccc")); request.setAttribute("list",list); %>
<c:forEach var="person" items="${list }">
<%--将迭代的每个元素放在person变量当中 --%>
${person.name }<br/>
</c:forEach>
<br>
<% Map map=new HashMap(); map.put("aa",new Person("aaaa")); map.put("bb",new Person("bbbb")); map.put("cc",new Person("cccc")); map.put("dd",new Person("dddd")); map.put("1111",new Person("eeee")); request.setAttribute("map123",map); %>
<c:forEach var="entry" items="${map123}">
<%--对map的迭代实际上是对map.entrySet返回的set<Map.entry>结合进行迭代 --%>
${entry.key} : ${entry.value.name} <br/>
<%--判断标签 --%>
</c:forEach>
<c:if test="${user!=null}">
欢迎您:${user.username}
</c:if>
<c:if test="${user==null}">
用户名：<input type="text"/>
密码：<input type="password"/>
</c:if>
</body>
</html>