JSP EL表达式

最新推荐文章于 2025-06-20 00:00:00 发布

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本文介绍了EL表达式的使用方法，包括基本运算符、数组访问及变量读取等，并提供了禁用EL表达式的两种配置方式。

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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>EL表达式的介绍</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">

  </head>
  
  <body>
    <% 
    	session.setAttribute("username" , "libinxuan"); 
    	String[] week = {"星期一","星期二","星期三","星期四","星期五","星期六","星期天"};
    	session.setAttribute("week", week);
    %>
    <table border="1">
    	<tr>
    		<td><b>运算符</b></td>
    		<td><b>EL 表达式</b></td>
    		<td><b>运算结果</b></td>
    	</tr>
    	<tr>
    		<td>加法</td>
    		<td>\${10+10}</td>
    		<td>${10+10}</td>
    	</tr>
    	<tr>
    		<td>比较</td>
    		<td>\${101 gt 10}</td>
    		<td>${101 > 10}</td>
    	</tr>
    	<tr>
    		<td>比较</td>
    		<td>\${10 == 10}</td>
    		<td>${10 == 10}</td>
    	</tr>
    	<tr>
    		<td>读取数组</td>
    		<td>\${sessionScope.username}</td>
    		<td>${sessionScope.username}</td>
    	</tr>
    	<tr>
    		<td>读取变量</td>
    		<td>\${sessionScope.week['1']}</td>
    		<td>${sessionScope.week['1']}</td>
    	</tr>
    </table>
  </body>
</html>

设置不使用EL表达式有两种方法：

jsp中修改%@page isELIgnored="true" %

web.xml修改

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	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-app_2_5.xsd">
  
  <jsp-config>
  	<jsp-property-group>
  		<url-pattern>*.jsp</url-pattern>
  		<el-ignored>true</el-ignored>
  	</jsp-property-group>
  </jsp-config>
  
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>