JDBC+Servlet+JSP整合开发之27.JSP自定义标签

�C简介
�C标签接口和类
�C标签的分类
�C标签实例
? HelloWorld 简单标签
?有属性的标签
?有标签体，有属性的标签
?嵌套标签
?循环标签

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? 简介
�C标签在JSP页面中被调用
�C标签对应一个Java 处理类，来处理标签逻辑
�C好处是，是页面中尽量少写代码

? 标签接口和类
�CJSP所有标签都实现了javax.servlet.jsp.JspTag接口
?这个接口有两个之间接口：
? SimpleTag
�CJSP 2.0 中新增的接口
? Tag
�C是一个经典的必须实现的接口
�C它有一个直接接口是IterationTag

? 标签的分类
�C不带属性和标签体的简单标签
�C不带标签体，但是有属性的标签
�C带标签体，且有属性的标签

? 标签实例
�CHelloWorld 简单标签
�C有属性的标签
�C有标签体，有属性的标签
�C嵌套标签
�C循环标签

先来看下如何实现简单的标签哈~

MyTag.java

此类实现了Tag接口

 

MyTag.tld

MyTag.jsp

测试：

下面我们继承TagSupport抽象类，这样更简单一些哈~

MyTag2.java

MyTag.tld

MyTag2.jsp

测试：

下面我们输出一个下拉列表哈~

MyTag3.java

MyTag.tld

MyTag.jsp

测试：

 

下面从数据库取出下拉列表内容，并将其定义为标签。

 

MyTag.tld

MyTag.jsp

MyTag4.java

PositionService.java

ConnectionUtil.java

package com.michael.tag;    

import java.sql.Connection;    
import java.sql.DriverManager;    
import java.util.Properties;    

public class ConnectionUtil {    

         /**    
         * @param args    
         */    
         public static void main(String[] args) {    
                ConnectionUtil cu = new ConnectionUtil();    
                System.out.println(cu.openConnection());    
        }    
         public Connection openConnection() {    
                String url = "";    
                String driver = "";    
                String user = "";    
                String password = "";    
                Properties prop = new Properties();    
                 try {    
                        prop.load( this.getClass().getClassLoader().getResourceAsStream( "DBConfig.properties"));    
                        driver = prop.getProperty( "driver");    
                        url = prop.getProperty( "url");    
                        user = prop.getProperty( "user");    
                        password = prop.getProperty( "password");    
                        Class.forName(driver);    
                        Connection conn = DriverManager.getConnection(    
                                        url, user, password);    
                         return conn;    
                } catch (Exception e) {    
                        e.printStackTrace();    
                }    
                 return null;    
        }    
         public Connection getConnection(String driver, String url, String user,    
                        String password) {    
                 // Class.forName()    
                 try {    
                        Class.forName(driver);    
                         // DriverManager get connection    
                        Connection conn = DriverManager.getConnection(url, user, password);    
                         return conn;    
                } catch (Exception e) {    
                        e.printStackTrace();    
                }    
                 return null;    
        }    

         public Connection getConnection() {    
                 // Class.forName()    
                 try {    
                        Class.forName( "com.mysql.jdbc.Driver");    
                         // DriverManager get connection    
                        Connection conn = DriverManager.getConnection(    
                                         "jdbc:mysql://localhost:3306/jsp_db", "root", "963963");    
                        return conn;    
                } catch (Exception e) {    
                        e.printStackTrace();    
                }    
                return null;    
        }    

}

Position.java

DBConfig.properties

测试：

数据库中有四条记录，我们看下能不能取出来哈~

下面我们在数据库中增加一条记录测试一下哈~

 

 

以上四个标签都是没有属性的，下面我们测试有属性的标签，传递一个参数，循环的输出哈~

MyTag5.java

MyTag.tld

MyTag.jsp

测试：

下面测试有标签体的标签，我们可以实现一个接口或者继承一个类哈~

先看实现接口的方法

MyTag6.java

package com.michael.tag;    

import java.io.IOException;    

import javax.servlet.jsp.JspException;    
import javax.servlet.jsp.PageContext;    
import javax.servlet.jsp.tagext.BodyContent;    
import javax.servlet.jsp.tagext.BodyTag;    
import javax.servlet.jsp.tagext.Tag;    

public class MyTag6 implements BodyTag{    
         private int count;    
         private BodyContent bodyContent;    
         public void setCount( int count) {    
                 this.count = count;    
        }    
         public void doInitBody() throws JspException {    
        }    

         public void setBodyContent(BodyContent bodyContent) {    
                 this.bodyContent = bodyContent;    
        }    

         public int doAfterBody() throws JspException {    
                 if(count>1){    
                        count--;    
                         return this.EVAL_BODY_AGAIN;    
                }    
                 return this.SKIP_BODY;    
        }    

         public int doEndTag() throws JspException {    
                 try {    
                         if(bodyContent!= null)    
                        bodyContent.print(bodyContent.getEnclosingWriter());    
                } catch (IOException e) {    
                        e.printStackTrace();    
                }    
                 return this.EVAL_PAGE;    
        }    

         public int doStartTag() throws JspException {    
                 if(count>0){    
                         return this.EVAL_BODY_INCLUDE;    
                }    
                 return this.SKIP_BODY;    
        }    

         public Tag getParent() {    
                 return null;    
        }    

         public void release() {    
        }    

         public void setPageContext(PageContext pageContext) {    
        }    

         public void setParent(Tag tag) {    
        }    
}

MyTag.tld

MyTag.jsp

测试：

下面我们实现抽象类来测试有标签体的标签哈~

MyTag7.java

MyTag.tld

MyTag.jsp

测试：

在JSP2.0中还有一个新特征，具有SimpleTag接口，还有针对这个接口的实现类，如果使用这个接口就更方法了哈~

MyTag8.java

MyTag.tld

MyTag.jsp

测试：

下面我们实现针对这个接口的抽象类

MyTag9.java

MyTag.tld

MyTag.jsp

测试：

 

 

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