自定义EL表达式

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1、首先编写EL处理类 预定义为表达式的方法必须为 公共静态

package com.hkrt.demo;public class Util {public static int length(){return 100;}}

2、定义util.tld /WEB-INF/util.tld

<?xml version="1.0" encoding="UTF-8"?><taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3,org/2001/XMLSchema-instancce"xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/cml/ns/javaee/web-jsptaglibrary_2_1.xsd"><tlib-version>1.0</tlib-version><short-name>自定义EL</short-name><uri>http://www.icardpay.com/util</uri><function><description>Length</description><name>length</name><function-class>com.hkrt.demo.Util</function-class><function-signature>int length()</function-signature></function></taglib>

3、页面调用自定义EL

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%><%@taglib prefix="util" uri="/WEB-INF/util.tld"%><%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <base href="<%=basePath%>">        <title>My JSP 'index.jsp' starting page</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0">    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">-->  </head>    <body>    后面会输出自定义表达式的返回值 ${ util:length() }<br>  </body></html>