el表达式
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2022-04-07 21:01:01
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el表达式可以获取request，session，application中的属性值
<body>
<%
pageContext.setAttribute("info1","page范围的值");
request.setAttribute("info1","request范围的值");
session.setAttribute("info1","session范围的值");
application.setAttribute("info1","application范围的值");
%>
<h1>${info1 }</h1>
<%-- <h1>${info2 }</h1>
<h1>${info3 }</h1>
<h1>${info4 }</h1> --%>
</body>el表达式接收请求参数
param 单个参数
paramvalues 一组参数
<body>
<form action="el2.jsp" method="post">
<input type="text" name="name"/>
<input type="submit" value="提交el2.jsp"/>
</form>
<a href="el2.jsp?age=12">提交el2.jsp</a>
<form action="el2.jsp" method="post">
<input type="checkbox" name="hobby" value="java语言"/>java语言
<input type="checkbox" name="hobby" value="C#语言"/>C#语言
<input type="checkbox" name="hobby" value="php语言"/>php语言
<input type="submit" value="提交el2.jsp"/>
</form>
</body>el2.jsp
<body>
<%
request.setCharacterEncoding("utf-8");
%>
<h1>姓名：${param.name }</h1>
<h1>年龄：${param.age }</h1>
<h1>爱好一：${paramValues.hobby[0] }</h1>
<h1>爱好二：${paramValues.hobby[1] }</h1>
<h1>爱好三：${paramValues.hobby[2] }</h1>
</body>对象操作
<%@ page import="com.model.People" %>
<body>
<%
People zhangsan=new People();
zhangsan.setId(1);
zhangsan.setName("张三");
zhangsan.setAge(20);
request.setAttribute("zhangsan",zhangsan);
%>
<h1>编号：${zhangsan.id }</h1>
<h1>姓名：${zhangsan.name }</h1>
<h1>年龄：${zhangsan.age }</h1>
</body>el获取数组中的元素
<body>
<%
List all=new LinkedList();
all.add(0,"元素一");
all.add(1,"元素二");
all.add(2,"元素三");
request.setAttribute("all",all);
%>
<h1>${all[0] }</h1>
<h1>${all[1] }</h1>
<h1>${all[2] }</h1>
</body>el运算符
<body>
<%
request.setAttribute("num1",10);
request.setAttribute("num2",3);
request.setAttribute("flag1",true);
request.setAttribute("flag2",false);
%>
<h1>算数运算符</h1>
<h2>num1=${num1 },num2=${num2 }</h2>
<h2>num1+num2=${num1+num2 }</h2>
<h2>num1-num2=${num1-num2 }</h2>
<h2>num1*num2=${num1*num2 }</h2>
<h2>num1/num2=${num1/num2 }</h2>
<h2>num1%num2=${num1%num2 }</h2>
<h2>num1*(num1-num2)=${num1*(num1-num2) }</h2>
<h1>关系运算符</h1>
<h2>flag1=${flag1 },flag2=${flag2 }</h2>
<h2>与操作flag1 && flage2：${flag1 && flage2 }</h2>
<h2>或操作flag1 || flage2：${flag1 || flage2 }</h2>
<h2>非操作!flag1：${!flag1}</h2>
<h1>三目运算符</h1>
<h2>三目操作：num1>num2：${num1>num2?"yes":"no" }</h2>
<h1>empty关键字</h1>
<h2>判断空操作：${empty num1 }</h2>
</body>
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