JSP标签的作用？如何定义？

参考答案

JSP标签的作用主要是将与 页面的显示和控制 相关的逻辑进行封装和重用。

参考示例

1. 首先编写java类，继承SimpleTagSupport类，并重写doTag()方法：

package web;

import java.io.IOException;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class HelloTag extends SimpleTagSupport {

    private String message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    @Override
    public void doTag() throws JspException, IOException {
        JspWriter out = this.getJspContext().getOut();
        out.println("<h1>Hello, " + message + "</h1>");
    }
}

2. 编写helloTag.tld文件，放入WEB-INF目录下

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE taglib PUBLIC 
  "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.2//EN" 
  "http://java.sun.com/dtd/web-jsptaglibrary_1_2.dtd" >
<taglib>
  <tlib-version>1.0</tlib-version>
  <jsp-version>1.2</jsp-version>
  <short-name>short-name</short-name>
  <uri>http://www.xingxue.com</uri>
  <tag>
    <name>helloTag</name>
    <tag-class>web.HelloTag</tag-class>
    <attribute>
        <name>message</name>
        <required>true</required>
        <rtexprvalue>true</rtexprvalue>
    </attribute>
    <body-content>empty</body-content>
  </tag>
</taglib>

3. 编写jsp，通过uri引用tag

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="m" uri="http://www.xingxue.com" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>标签示例</title>
</head>
<body>
    <m:helloTag message="Tom"/>
</body>
</html>

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