传统标签库功能实例

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>

posted on 2012-01-26 20:51 sp2012 阅读(268) 评论(0) 编辑收藏举报