java(jsp)的自定义标签

java(jsp)的自定义标签

参考地址:http://dongguoh.iteye.com/blog/100782

TagSupport与BodyTagSupport的区别主要是标签处理类是否需要与标签体交互
用TagSupport实现的标签,都可以用BodyTagSupport来实现,因为BodyTagSupport继承了TagSupport。

doStartTag()方法是遇到标签开始时会呼叫的方法,其合法的返回值是EVAL_BODY_INCLUDE与SKIP_BODY,前者表示将显示标签间的文字,后者表示不显示标签间的文字;doEndTag()方法是在遇到标签结束时呼叫的方法,其合法的返回值是EVAL_PAGE 与 SKIP_PAGE,前者表示处理完标签后继续执行以下的JSP网页,后者是表示不处理接下来的JSP网页


首先是核心类,继承自BodyTagSupport类,:
ppackage cn.tag;

import java.io.IOException;
import java.util.Map;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyTagSupport;


public class TestTag extends BodyTagSupport {

	private static final long serialVersionUID = -5663050580910865400L;
	/**
	 * 可以在这里进行一些初始化的工作
	 */
	public int doStartTag() throws JspException {		 
		System.out.println("----doStartTag()----");
		JspWriter out = this.pageContext.getOut();
		try {
				out.println("before");
		} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
		}
		return this.EVAL_BODY_INCLUDE;
	 }
	 /**
	  * 核心处理标签的地方,业务逻辑在此实现,如:分页,根据参数返回给前台的值等等
	  */
	 public int doEndTag() throws JspException {
		 JspWriter out = this.pageContext.getOut(); 
		 System.out.println("----doEndTag()----"); 
		 
		 /**
		  * 获取参数
		  */
		 Map map=this.pageContext.getRequest().getParameterMap();
		 if(map==null){
			 System.out.println("map is null");
		 }else{
			 System.out.println("map not null");
			 System.out.println(map.size());
		 }
		 try {
			out.println("end");
		} catch (IOException e) {
			System.out.println(e.getMessage());
			e.printStackTrace();
		}
	     return super.doEndTag();
	 }
}


定义testTag.tld,貌似有些项是必需的,如下所示:
<?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>测试</description> 
  <tlib-version>1.1</tlib-version>
  <short-name>tt</short-name>  
  <uri>/testTag</uri>
   <tag>
		<name>test</name>
		<tag-class>cn.tag.TestTag</tag-class>
		<body-content>JSP</body-content>
	</tag>
</taglib>


测试页面,关键是要引入testTag.tld文件:
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="/WEB-INF/testTag.tld" prefix="tags"%> 
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'test.jsp' starting page</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>   	
    <tags:test >测试</tags:test>
  </body>
</html>


显示结果:

控制台:
----doStartTag()----
----doEndTag()----
map not null

页面:
before 测试end 

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