JSTL 自定义标签

编写描述标签的tld文件，把这个文件放到web-inf/目录下，才能在jsp页面上调用自定义的标签

package test.yz;
 
import java.io.IOException;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspContext;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.JspTag;
import javax.servlet.jsp.tagext.SimpleTag;
 
public class Handsome implements SimpleTag {
 
    private PageContext pageContext;
 
    @Override
    public void doTag() throws JspException, IOException {
        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
        JspWriter out = pageContext.getOut();
        out.print(" handsome boy");
        System.out.println(" handsome boy");
    }
 
    @Override
    public JspTag getParent() {
        return null;
    }
 
    @Override
    public void setJspBody(JspFragment arg0) {
 
    }
 
    @Override
    public void setJspContext(JspContext jspContext) {
        pageContext = (PageContext)jspContext;
 
    }
 
    @Override
    public void setParent(JspTag arg0) {
 
    }
 
}

package test.yz;
 
import java.io.IOException;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspContext;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.JspFragment;
import javax.servlet.jsp.tagext.JspTag;
import javax.servlet.jsp.tagext.SimpleTag;
 
public class SumTag implements SimpleTag {
 
    private PageContext pageContext;
    private int num1;
    private int num2;
 
    public void setNum1(int num1) {
        this.num1 = num1;
    }
 
    public void setNum2(int num2) {
        this.num2 = num2;
    }
 
    @Override
    public void doTag() throws JspException, IOException {
        // TODO Auto-generated method stub
        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
        JspWriter out = pageContext.getOut();
        out.print(num1+num2);
    }
 
    @Override
    public JspTag getParent() {
        // TODO Auto-generated method stub
        return null;
    }
 
    @Override
    public void setJspBody(JspFragment arg0) {
        // TODO Auto-generated method stub
 
    }
 
    @Override
    public void setJspContext(JspContext arg0) {
 
        pageContext = (PageContext)arg0;
 
    }
 
    @Override
    public void setParent(JspTag arg0) {
        // TODO Auto-generated method stub
 
    }
 
}

<?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>JSTL 1.0 core library</description>
    <display-name>JSTL core</display-name>
    <tlib-version>1.0</tlib-version>
    <short-name>lf</short-name> <!-- 默认的前缀名 -->
    <uri>http://java.lf.com/handsome</uri> <!-- 指定访问路径 -->
 
      <tag>
          <name>hs</name> <!-- 标签名 -->
          <tag-class>test.yz.Handsome</tag-class><!-- 自定义类的全称 -->
          <body-content>empty</body-content>
      </tag>
 
      <!-- 配置属性标签 -->
      <tag>
          <name>sum</name>
          <tag-class>test.yz.SumTag</tag-class>
          <body-content>scriptless</body-content>
 
          <attribute>
              <name>num1</name>
              <required>true</required>
              <rtexprvalue>true</rtexprvalue> <!-- true的话jsp中该属性只可以为表达式，false只能为静态值 -->
              <type>java.lang.Integer</type> <!-- 指明参数的类型 -->
          </attribute>
 
          <attribute>
              <name>num2</name>
              <required>true</required>
              <rtexprvalue>true</rtexprvalue> <!-- true的话jsp中该属性只可以为表达式，false只能为静态值 -->
              <type>java.lang.Integer</type> <!-- 指明参数的类型 -->
          </attribute>
      </tag>
 
</taglib>  

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="lf" uri="http://java.lf.com/handsome" %>
 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
 
    <title>test</title>
 
  </head>
 
  <body>
 
      <!-- 测试自定义标签 -->
     <h1><lf:hs/></h1>
 
     <lf:sum num2="2" num1="3"></lf:sum>
 
  </body>
 
</html>