EL测试

2021-08-11 11:09:35
421次极悦

index.jsp

<body>
<%
	request.setAttribute("name", "zhangsan");
	pageContext.setAttribute("name", "lisi");
%>
<h1> ${name}</h1>
<!-- name取值,会按以下顺序从小范围到大范围去查找 -->
<!-- 1.pageScope 2.requestScope 3.sessionScope 4.applicationScope
如果按照以下顺序都没有查找到,就返回空字符串 -->
------ ${h} -------
  <hr>
<!-- 可以通过域获取对应的值 -->
 ${requestScope.name}
 <hr> 
 <%
 	People people = new People("zhangsan");
 	pageContext.setAttribute("user1", people);
 %>
	 ${user1.name }
	 <hr>
<%
	People people2 = new People("zhangsan");
	People people3 = new People("lisi");
	List<People> list = new ArrayList<>();
	list.add(people2);
	list.add(people3);
	pageContext.setAttribute("list", list);
%>
  	${list[1].name}
  	<hr>  	  	
  	<%
  		People people4 = new People("zhangsan");
  		People people5 = new People("lisi");
  		HashMap<String,People> map = new HashMap<>();
  		map.put("1", people4);
  		map.put("2", people5);
  		pageContext.setAttribute("map", map);
  	%>
		${map['1'].name }	
	<%
		pageContext.setAttribute("a", 2);
		pageContext.setAttribute("b", 5);
		String zhangsan = null;
		pageContext.setAttribute("str", zhangsan);
	%>	
	<!-- EL支持算数运算符 -->
	${a+b} <!-- +-*/ -->
	<!-- EL支持比较运算符 -->
	${a>b} <!-- > < >= <= ==  -->
	<!-- El支持逻辑运算符 -->
	${a>1 && b<8}
	${a>1 and b<10} <!-- and or -->	
	${str == null}	
	${str eq "123"} <!-- str.euqals("123") -->
	<!-- 空判断 -->
	${empty str} <!-- if(str == null || str.equals("")) -->	
	<!-- 非空判断 -->
	${not empty str}
	<hr>
</body>

测试结果:

<body>
<form action="index2.jsp" method="post">
	name:<input type="text" name="username" /><br>
	password:<input type="text" name="password"/><br>
	favorite:<input type="checkbox" name="fav" value="abc"/>abc<br>
			<input type="checkbox" name="fav" value="qwe"/>qwe<br>
			<input type="submit" >
</form>
</body>

index2.jsp

<body>
	<!-- EL支持通过参数取值,格式:${param.参数名} -->
	<%
	  String[] favs = request.getParameterValues("fav");
		request.setCharacterEncoding("utf-8");
		response.setCharacterEncoding("utf-8");
	%>	
	name:${param.username}
	password:${param.password}
	<hr>
	<!-- ${paramValues.参数名[index]} 取得的是参数名一样的一组值 -->
	fav:${paramValues.fav[0]}
	<hr>
	<%
		Cookie cookie = new Cookie("user","zhangsan");
		response.addCookie(cookie);
	%>	
	<!-- ${cookie对象.cookie名.name}
		${cookie对象.cookie名.value} -->
	${cookie.user.name}
	${cookie.user.value}
	<hr>
	<!-- 从请求头获取数据 -->
	${header.Host}
	${headerValues.cookie[0]}
	<hr>
</body>

测试结果: