简化的JSP自定义标签

    JSP2.0的自定义标签更加简单,无需重写繁琐的doStrartTag和doEndTag等方法,即使是带标签体的标签,也与不带标签体的标签处理方法完全相同,无须重写doAfterBody等方法,通常只需重写doTag方法。

    案例说明:功能迭代其标签和简单标签

1.书写标签处理类

   

package mytag;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

/**
 * 简单标签类
 */	
public class HelloWorldSimpleTag extends SimpleTagSupport{
	@Override
	public void doTag() throws JspException, IOException {
		getJspContext().getOut().write("HelloWorldSimpleTag");
	}
}





package mytag;

import java.io.IOException;
import java.util.Collection;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.SimpleTagSupport;
/**
 *	简单标签处理类,继承SimpleTagSupport
 */
public class MyIteatorTag extends SimpleTagSupport {
	//标签属性
	private String bean;

	public String getBean() {
		return bean;
	}

	public void setBean(String bean) {
		this.bean = bean;
	}
	
	//标签的处理方法,简单标签处理类,只需要重写doTag方法
	@Override
	public void doTag() throws JspException, IOException {
		//从page scope中获取名为bean的集合属性
		Collection<String> itemList = (Collection<String>)getJspContext().getAttribute(bean);
		//遍历集合
		for(String s:itemList){
			//将集合的元素设置到page范围
			getJspContext().setAttribute("item", s);
			getJspBody().invoke(null);
		}
	}
}

 

2.创建TLD

 

<?xml version="1.0" encoding="GBK"?>
<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">
    <!-- 标签版本 -->
    <tlib-version>1.0</tlib-version>
    <!-- 标签名称 -->
    <short-name>MyIteatorTag</short-name>
    <!-- 定义第一个个标签 -->
    <tag>
    	<!-- 定义标签名称 -->
    	<name>helloWorld</name>
    	<!-- 定义标签的处理类 -->
    	<tag-class>mytag.HelloWorldSimpleTag</tag-class>
    	<!-- 定义标签体类空 -->
    	<body-content>empty</body-content>
    </tag>  
    <!-- 定义第二个标签 -->
    <tag>
    	<!-- 定义标签名称 -->
    	<name>iterator</name>
    	<!-- 定义标签处理类 -->
    	<tag-class>mytag.MyIteatorTag</tag-class>
    	<!-- 定义标签体,该标签体是不允许脚本的标签 -->
    	<body-content>scriptless</body-content>
    	<!-- 定义标签属性 -->
    	<attribute>
    		<name>bean</name>
    		<required>true</required>
    		<rtexprvalue>true</rtexprvalue>
    	</attribute>
    </tag>
</taglib>

 

3.配置WEB.XML (可省略)

  

<web-app version="2.5" 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-app_2_5.xsd">
	<jsp-config>
		<taglib>
			<taglib-uri>/iterator</taglib-uri>
			<taglib-location>/WEB-INF/MyiteratorTag.tld</taglib-location>
		</taglib>
	</jsp-config>
	<welcome-file-list>
		<welcome-file>index.jsp</welcome-file>
	</welcome-file-list>
</web-app>

 

4.JSP调用

 

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@ taglib uri="/iterator" prefix="iterss" %> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>表达式语言-逻辑运算符</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>
  <body>
	<iterss:helloWorld/>
	<%
		//创建输出对象
			List<String> a = new ArrayList<String>();
			a.add("a");
			a.add("b");
			a.add("c");
			//将a放入 page 范围内
			pageContext.setAttribute("a", a);
	%>
	<iterss:iterator bean="a">
		${item }
	</iterss:iterator>
  </body>
</html>

 

 

 

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