开发带标签体的标签实战

偏执的太偏执、 2021-07-24 19:59 366阅读 0赞

**一 开发自定义标签**

package lee;
    
    import javax.servlet.jsp.tagext.*;
    import javax.servlet.jsp.*;
    import java.io.*;
    import java.sql.*;
    import java.util.*;
    
    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);
            }
        }
    }

**二 建立TLD文件**

<?xml version="1.0" encoding="GBK"?>
    
    <taglib xmlns="http://xmlns.jcp.org/xml/ns/javaee"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
        http://xmlns.jcp.org/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
        version="2.1">
        <tlib-version>1.0</tlib-version>
        <short-name>mytaglib</short-name>
        
        <uri>http://www.crazyit.org/mytaglib</uri>
    
        
        <tag>
            
            <name>iterator</name>
            
            <tag-class>lee.IteratorTag</tag-class>
            
            <body-content>scriptless</body-content>
            
            <attribute>
                <name>collection</name>
                <required>true</required>
                <fragment>true</fragment>
            </attribute>
            
            <attribute>
                <name>item</name>
                <required>true</required>
                <fragment>true</fragment>
            </attribute>
        </tag>
     
    </taglib>

**三 使用标签**

<%@ page contentType="text/html; charset=GBK" language="java" errorPage="" %>
    <%@ page import="java.util.*"%>
    
    <%@ taglib uri="http://www.crazyit.org/mytaglib" prefix="mytag"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
        "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title> 带标签体的标签-迭代器标签 </title>
        <meta name="website" content="http://www.crazyit.org" />
    </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">
            
            <mytag:iterator collection="a" item="item">
            <tr>
                <td>${pageScope.item}</td>
            <tr>
            </mytag:iterator>
        </table>
    </body>
    </html>

**四 测试**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NoZW5ncWl1bWluZw_size_16_color_FFFFFF_t_70]: /images/20210724/097fde5025074a2795a4a52b2dd5e86d.png