<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<%@page import="java.util.HashMap"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
request.setAttribute("somemap", new HashMap());
%>
<c:remove var="somemap" />
${ somemap == null ? ‘somemap 已经被删除‘ : ‘somemap 没有被删除‘ }
</body>
</html>
原文：http://www.cnblogs.com/Nickzerui/p/4546734.html