心得11--jsp自定义标签案例分析

1、演示传统自定义标签(jsp2.0以前的)

使用自定义标签控制页面内容(标签体)是否输出,利用doStartTag()的返回值控制

return this.SKIP_BODY; //忽略标签体

return this.EVAL_BODY_INCLUDE; //执行标签体

控制整个jsp的输出利用doEndTag()的返回值控制

return this.SKIP_PAGE;  //跳过页面标签后余下的jsp代码

return this.EVAL_PAGE; //继续执行余下jsp代码

自定义标签实现内容(标签体)循环输出利用Tag子接口Iteration中定义的doAfterBody()和返回值EVAL_BODY_AGAIN,SKIP_BODY实现

先覆盖doStartTag()方法,返回EVAL_BODY_INCLUDE

覆盖doAfterBody()

public int doAfterBody() throws JspException {
	times++;
	int result = this.EVAL_BODY_AGAIN;
	if(times>4){
		result = this.SKIP_BODY;
	}
	return result;
}

自定义标签修改内容(标签体)EVAL_BODY_BUFFERED;
标签处理类:
继承BodyTagSupport
覆盖doStartTag(),并返回EVAL_BODY_BUFFERED;
覆盖doEndTag()
public int doEndTag() throws JspException {
	BodyContent bc = this.getBodyContent();
	String c = bc.getString();
	c = c.toUpperCase();
	JspWriter out = this.pageContext.getOut();
	try {
		out.write(c);
	} catch (IOException e) {
		throw new RuntimeException(e);
	}
	return this.EVAL_PAGE;
}
2、需求:实现一个自定义标签功能:判断一个YYYY-MM-DD格式的日期修改为下面格式输出
年:YYYY
月:MM
日:DD
  分析:
自定义标签处理类(Demo5.java)

package com.csdn.web.tag;

import java.io.IOException;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.Tag;

public class Demo5 extends BodyTagSupport {
	
	@Override
	public int doEndTag() throws JspException {
		BodyContent bc = this.getBodyContent();
		String b = bc.getString();
		String[] data = b.split("-");
		JspWriter out = this.pageContext.getOut();
		try {
			out.println("年:"+data[0]+"<br>");
			out.println("月:"+data[1]+"<br>");
			out.println("日:"+data[2]+"<br>");
		} catch (IOException e) {
			e.printStackTrace();
		}
		return Tag.EVAL_PAGE;
	}
}


要转换的显示时间6.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib uri="/csdn" prefix="csdn"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>转换日期格式并输出</title>
  </head>
  
  <body>
    <csdn:demo5>2012-11-17</csdn:demo5>
  </body>
</html>

对应的标签模版csdn.tld

<?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">
	<tlib-version>1.0</tlib-version>
	<short-name>csdn</short-name>
	<uri>/csdn</uri>
	<tag>
		<name>demo5</name>
		<tag-class>com.csdn.web.tag.Demo5</tag-class>
		<body-content>JSP</body-content>
	</tag>
</taglib>


 

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