javaweb之自定义标签库——if标签

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我是靠谱客的博主炙热夏天，最近开发中收集的这篇文章主要介绍javaweb之自定义标签库——if标签，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="/example" prefix="c" %>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>开发if标签（是否执行标签体内容案例）</title>
  </head>
  
  <body>
  	<%--模拟servlet的代码 --%>
  	<% 
  		request.getSession().setAttribute("user", "aaa");
  	%>
  	
	<c:if test="${user==null }">
    	aaaaaa
    </c:if>
    
    <c:if test="${user!=null }">
    	bbbbbb
    </c:if>
  </body>
</html>

package cn.itcast.web.tag.example;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
//开发if标签
public class IfTag extends SimpleTagSupport {
	private boolean test;

	public void setTest(boolean test) {
		this.test = test;
	}
	
	//如果test是true输出标签体
	@Override
	public void doTag() throws JspException, IOException {
		if(test) {
			this.getJspBody().invoke(null);
		}
	}
	
}

<?xml version="1.0" encoding="UTF-8" ?>

<taglib 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-jsptaglibrary_2_0.xsd"
    version="2.0">
    <description>A tag library exercising SimpleTag handlers.</description>
    <tlib-version>1.0</tlib-version>
    <short-name>example</short-name><!-- 描述文件的名称 -->
    <uri>/example</uri><!-- 描述文件的uri -->
    
    
    <tag>
        <name>referer</name>
        <tag-class>cn.itcast.web.tag.example.RefererTag</tag-class>
        <body-content>empty</body-content>
        <attribute>
        	<name>site</name>
        	<required>true</required>
        	<rtexprvalue>true</rtexprvalue>
        </attribute>
        
        <attribute>
        	<name>page</name>
        	<required>true</required>
        	<rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
    
    <tag>
        <name>if</name>
        <tag-class>cn.itcast.web.tag.example.IfTag</tag-class>
        <body-content>scriptless</body-content>
        <attribute>
        	<name>test</name>
        	<required>true</required>
        	<rtexprvalue>true</rtexprvalue>
        </attribute>
    </tag>
   
</taglib>