JSP标签库实战-优快云博客

传统标签库，也就是JSP1.0的时候，主要有Tag,BodyTag, IterationTag，这三个接口，分别实现不同的功能。

1.可以实现控制是否显示标签体里面的内容

首先必须写一个类实现Tag接口，代码如下

package com.bird.web.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * 控制标签是否显示
 * @author Bird
 *
 */
public class TagDemo1 extends TagSupport{

	private static final long serialVersionUID = 1L;

	@Override
	public int doStartTag() throws JspException {
		return Tag.SKIP_BODY;
	}
	
	
}

然后将标签的声明写入到tld文件中

<?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>Bird</short-name>
    <uri>http://www.bird.net</uri>
    
    
    <tag>
        <name>viewIP</name>
		<tag-class>com.bird.web.tag.ViewIPTag</tag-class>
		<body-content>empty</body-content>
    </tag>
    
    
    <tag>
        <name>tagDemo1</name>
		<tag-class>com.bird.web.tag.TagDemo1</tag-class>
		<body-content>JSP</body-content>
    </tag>
    
    <tag>
        <name>tagDemo2</name>
		<tag-class>com.bird.web.tag.TagDemo2</tag-class>
		<body-content>empty</body-content>
    </tag>
    
    <tag>
        <name>tagDemo3</name>
		<tag-class>com.bird.web.tag.TagDemo3</tag-class>
		<body-content>JSP</body-content>
    </tag>
    
    
     <tag>
        <name>tagDemo4</name>
		<tag-class>com.bird.web.tag.TagDemo4</tag-class>
		<body-content>JSP</body-content>
    </tag>
    </taglib>

然后就可以在JSP页面中使用这个标签了

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri="http://www.bird.net" prefix="bird"%>
<bird:tagDemo2/>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>用标签控制整个JSP是否输出</title>
    
  </head>
  
  <body>
  aaaaaaaaaaaaaaaaaa
  </body>
</html>

2.使用标签控制JSP页面下面的内容是否继续执行

package com.bird.web.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * 控制下面的页面是否继续执行
 * @author Bird
 *
 */
public class TagDemo2 extends TagSupport {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Override
	public int doEndTag() throws JspException {
		return Tag.EVAL_PAGE;
	}

	
	
}

然后使用这个标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri="http://www.bird.net" prefix="bird"%>

<bird:tagDemo2/>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>用标签控制整个JSP是否输出</title>
    
  </head>
  
  <body>
  aaaaaaaaaaaaaaaaaa
  </body>
</html>

3.使用标签控制标签体里面的内容执行多次

package com.bird.web.tag;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.IterationTag;
import javax.servlet.jsp.tagext.Tag;
import javax.servlet.jsp.tagext.TagSupport;

/**
 * 控制标签体里面的内容执行多次
 * @author Bird
 *
 */
public class TagDemo3 extends TagSupport{

	private static final long serialVersionUID = 1L;
	
	private int count = 5;
	@Override
	public int doAfterBody() throws JspException {
		count--;
		if(count > 0)
			return IterationTag.EVAL_BODY_AGAIN;
		else
			return IterationTag.SKIP_BODY;
	}
	@Override
	public int doStartTag() throws JspException {
		return Tag.EVAL_BODY_INCLUDE;
	}	
	
	
	
	
	
	
		
}

然后使用这个标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri="http://www.bird.net" prefix="bird"%>


<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>控制某一部分内容重复执行</title>
    
  </head>
  
  <body>
  <bird:tagDemo3>
  			小白<br/>
  </bird:tagDemo3>
  </body>
</html>

4.修改JSP页面的内容再输出

package com.bird.web.tag;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTag;
import javax.servlet.jsp.tagext.BodyTagSupport;
import javax.servlet.jsp.tagext.Tag;

/**
 * 修改标签体内容
 * @author Bird
 *
 */
public class TagDemo4 extends BodyTagSupport{

	private static final long serialVersionUID = 1L;

	@Override
	public int doStartTag() throws JspException {
		return BodyTag.EVAL_BODY_BUFFERED;
	}

	@Override
	public int doEndTag() throws JspException {
		BodyContent bc = this.getBodyContent();
		String content = bc.getString();
		content = content.toUpperCase();
		
		try {
			this.pageContext.getOut().write(content);
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
		
		return Tag.EVAL_PAGE;
	}
	
	
	
	
}

最后使用这个标签

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<%@taglib uri="http://www.bird.net" prefix="bird"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>使用标签修改标签体里面的内容</title>
    
  </head>
  
  <body>
  <bird:tagDemo4>
  			aaa
  </bird:tagDemo4>
  </body>
</html>

传统标签库功能实例