吴裕雄--天生自然JAVA开发JSP-Servlet学习笔记：自定义标签-编写带标签体的标签

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 */
package lee;

import javax.servlet.jsp.tagext.*;
import javax.servlet.jsp.*;
import java.io.*;
import java.sql.*;
import java.util.*;

/**
 *
 * @author Administrator
 */
public class IteratorTag extends SimpleTagSupport {
    // 标签属性，用于指定需要被迭代的集合

    private String collection;
    // 标签属性，指定迭代集合元素，为集合元素指定的名称
    private String item;

    // collection的setter和getter方法
    public void setCollection(String collection) {
        this.collection = collection;
    }

    public String getCollection() {
        return this.collection;
    }
    // item的setter和getter方法

    public void setItem(String item) {
        this.item = item;
    }

    public String getItem() {
        return this.item;
    }
    // 标签的处理方法，标签处理类只需要重写doTag()方法

    public void doTag() throws JspException, IOException {
        // 从page scope中获取名为collection的集合
        Collection itemList = (Collection) getJspContext().
                getAttribute(collection);
        // 遍历集合
        for (Object s : itemList) {
            // 将集合的元素设置到page范围内
            getJspContext().setAttribute(item, s);
            // 输出标签体
            getJspBody().invoke(null);
        }
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd">
    <tlib-version>1.0</tlib-version>
    <short-name>mytaglib</short-name>
    <uri>/WEB-INF/tlds/mytaglib</uri>
    <!-- A validator verifies that the tags are used correctly at JSP
          translation time. Validator entries look like this: 
       <validator>
           <validator-class>com.mycompany.TagLibValidator</validator-class>
           <init-param>
              <param-name>parameter</param-name>
              <param-value>value</param-value>
           </init-param>
       </validator>
    -->
    <!-- A tag library can register Servlet Context event listeners in
         case it needs to react to such events. Listener entries look
         like this: 
      <listener>
          <listener-class>com.mycompany.TagLibListener</listener-class> 
      </listener>
    -->
    <!-- 定义第一个标签 -->
    <!-- 定义第一个标签 -->
    <tag>
        <!-- 定义标签名 -->
        <name>helloWorld</name>
        <!-- 定义标签处理类 -->
        <tag-class>lee.HelloWorldTag</tag-class>
        <!-- 定义标签体为空 -->
        <body-content>empty</body-content>
    </tag>

    <!-- 定义第二个标签 -->
    <tag>
        <!-- 定义标签名 -->
        <name>query</name>
        <!-- 定义标签处理类 -->
        <tag-class>lee.QueryTag</tag-class>
        <!-- 定义标签体为空 -->
        <body-content>empty</body-content>
        <!-- 配置标签属性:driver -->
        <attribute>
            <name>driver</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 配置标签属性:url -->
        <attribute>
            <name>url</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 配置标签属性:user -->
        <attribute>
            <name>user</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 配置标签属性:pass -->
        <attribute>
            <name>pass</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 配置标签属性:sql -->
        <attribute>
            <name>sql</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
    </tag>

    <!-- 定义第三个标签 -->
    <tag>
        <!-- 定义标签名 -->
        <name>iterator</name>
        <!-- 定义标签处理类 -->
        <tag-class>lee.IteratorTag</tag-class>
        <!-- 定义标签体不允许出现JSP脚本 -->
        <body-content>scriptless</body-content>
        <!-- 配置标签属性:collection -->
        <attribute>
            <name>collection</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
        <!-- 配置标签属性:item -->
        <attribute>
            <name>item</name> 
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
    </tag>
    <tag>
        <!-- 定义标签名 -->
        <name>fragment</name>
        <!-- 定义标签处理类 -->
        <tag-class>lee.FragmentTag</tag-class>
        <!-- 指定该标签不支持标签体 -->
        <body-content>empty</body-content>
        <!-- 定义标签属性：fragment -->
        <attribute>
            <name>fragment</name>
            <required>true</required>
            <fragment>true</fragment>
        </attribute>
    </tag>
    <!-- 定义接受动态属性的标签 -->
    <tag>
        <name>dynaAttr</name>
        <tag-class>lee.DynaAttributesTag</tag-class>
        <body-content>empty</body-content>
        <!-- 指定支持动态属性 -->
        <dynamic-attributes>true</dynamic-attributes>
    </tag>
</taglib>

<%-- 
    Document   : iteratorTag
    Created on : 2020-5-4, 23:29:17
    Author     : Administrator
--%>

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
<%@ page import="java.util.*"%>
<%@ taglib uri= "/WEB-INF/tlds/mytaglib" prefix="mytag"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title> 带标签体的标签-迭代器标签 </title>
    </head>
    <body>
        <h2>带标签体的标签-迭代器标签</h2><hr/>
        <%
            //创建一个List对象
            List<String> a = new ArrayList<String>();
            a.add("疯狂Java");
            a.add("www.crazyit.org");
            a.add("www.fkit.org");
            //将List对象放入page范围内
            pageContext.setAttribute("a", a);
        %>
        <table border="1" bgcolor="#aaaadd" width="300">
            <!-- 使用迭代器标签，对a集合进行迭代 -->
            <mytag:iterator collection="a" item="item">
                <tr>
                    <td>${pageScope.item}</td>
                <tr>
            </mytag:iterator>
        </table>
    </body>
</html>