步骤：
1.编写一个实现Tag接口的java类（标签处理类），派生自SimpleTagSupport，重写doTag()方法。getJspBody(),getJspContext(),invoke(null)
2.编写标签库描述符（tld）文件，在tld文件中对标签处理类进行描述。
3.调用
实例一：重复显示标签收中的内容
1.建类
package maya; import java.io.IOException; import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.*; public class TestTag extends SimpleTagSupport { private int count; public void setCount(int count){ this.count = count; } @Override public void doTag() throws JspException, IOException { JspFragment frag = this.getJspBody(); for(int i=0;i<count;i++){ frag.invoke(null); } } }
2.配置.tld
<?xml version="1.0" encoding="UTF-8"?> <taglib 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-jsptaglibrary_2_1.xsd" version="2.1"> <description>我自定义的标签</description> <display-name>XXX自定义标签</display-name> <tlib-version>1.0</tlib-version> <short-name>m</short-name> <uri>http://www.itnba.com/maya/myjstl</uri> <tag> <description> .....待写 </description> <name>show</name> <tag-class>maya.TestTag</tag-class> <body-content>scriptless</body-content> <attribute> <description> ...... </description> <name>count</name> <required>true</required><!--是否提交之前填写输入字段--> <rtexprvalue>false</rtexprvalue><!-- 是否可用jsp表达式 --> </attribute> </tag> </taglib>
3.在jsp中调用
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <%@ taglib prefix="m" uri="http://www.itnba.com/maya/myjstl" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Insert title here</title> </head> <body> <m:show count="3">//count在本例中属于必填字段 hello<br> </m:show> </body> </html>
运行结果：
hello
hello
hello
实例二：为标签中的内容加其它额外的属性或文字。
1.建类
package maya; import java.io.IOException; import javax.servlet.jsp.JspException; import javax.servlet.jsp.tagext.*; public class TestTag extends SimpleTagSupport { private String outerTagName="p"; public void setOuterTagName(String outerTagName) { this.outerTagName = outerTagName; } private int count; public void setCount(int count){ this.count = count; } @Override public void doTag() throws JspException, IOException { JspFragment frag = this.getJspBody(); this.getJspContext().getOut().write("<"+outerTagName+">");//括号里面可以改成任意文字，即为标签中的内容加其它额外的文字。例如：getJspContext().getOut().write("asdf") for(int i=0;i<count;i++){ frag.invoke(null); } this.getJspContext().getOut().write("</"+outerTagName+">"); } }
2.配置.tld
<?xml version="1.0" encoding="UTF-8"?> <taglib 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-jsptaglibrary_2_1.xsd" version="2.1"> <description>我自定义的标签</description> <display-name>XXX自定义标签</display-name> <tlib-version>1.0</tlib-version> <short-name>m</short-name> <uri>http://www.itnba.com/maya/myjstl</uri> <tag> <description> .....待写 </description> <name>show</name> <tag-class>maya.TestTag</tag-class> <body-content>scriptless</body-content> <attribute> <description> ...... </description> <name>outerTagName</name> <required>false</required><!--是否提交之前填写输入字段--> <rtexprvalue>false</rtexprvalue><!-- 是否可用jsp表达式 --> </attribute> <attribute> <description> ...... </description> <name>count</name> <required>true</required> <rtexprvalue>false</rtexprvalue> </attribute> </tag> </taglib>
3.在jsp中调用
<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%> <%@ taglib prefix="m" uri="http://www.itnba.com/maya/myjstl" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>Insert title here</title> </head> <body> <m:show count="3" outerTagName="h1"> hello<br> </m:show> </body> </html>
运行结果：