自定义EL标签

最新推荐文章于 2025-02-24 15:42:03 发布

转载最新推荐文章于 2025-02-24 15:42:03 发布 · 617 阅读

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本文介绍如何创建自定义的JSP标签，包括编写Java类、配置tld文件及在JSP页面中使用该标签的过程。通过示例展示了如何获取客户端IP地址。

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1、编写java类,该类继承TagSupport

MyTag.java

package com.servlet.util;
import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.TagSupport;

@SuppressWarnings("serial")
public class MyTag extends TagSupport {
	@Override
	public int doStartTag() throws JspException {
		HttpServletRequest request = (HttpServletRequest) this.pageContext.getRequest();
		JspWriter out = this.pageContext.getOut();
		
		String ip=request.getLocalAddr();
		try {
			out.print(ip);
		} catch (IOException e) {
			throw new RuntimeException();
		}
		return super.doStartTag();
	}
}

2、tld文件：tag.tld

<?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>itcast</short-name>
    <uri>/tag</uri>
    <tag>
        <name>viewIp</name>
        <tag-class>com.servlet.util.MyTag</tag-class>
        <body-content>empty</body-content>
    </tag>
</taglib>

3、jsp测试

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="t" uri="/tag"%>
<!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=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
	<t:viewIp/>
</body>
</html>