EL_获取域中存储的值和EL_获取域中存储的值_对象值

EL_获取域中存储的值

获取值
- el表达式只能从与域对象中获取值
- 语法：-${与名称.键名}：从指定域中获取指定键的值
  - 域名称：
    - pageScope -----> pageContext
    - requestScope -----> request
    - sessionScope -----> session
    - applicationScope -----> application (ServletContext)
      - 举例：在request域中存储了name=张三
      - 获取：$
  - ${键名}：标识依次从最小的域中查找是否有该键对应的值，直到找到为止

<%--
  Created by IntelliJ IDEA.
  User: lihaiyang
  Date: 2022/8/16
  Time: 14:02
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <%
        //在域中存储数据
        request.setAttribute("name1","张三");

        session.setAttribute("name2","李四");

        pageContext.setAttribute("name3","王五");

        application.setAttribute("name4","赵六");
    %>

    requestScope-->${requestScope.get("name1")}<br>
    sessionScope-->${sessionScope.get("name2")}<br>
    pageContext-->${pageContext.getAttribute("name3")}<br>
    pageScope-->${pageScope.get("name3")}<br>
    applicationScope-->${applicationScope.get("name4")}<br>

    requestScope-->${requestScope.name1}<br>
    sessionScope-->${sessionScope.name2}<br>
    pageScope-->${pageScope.name3}<br>
    applicationScope-->${applicationScope.name4}<br>
</body>
</html>

EL_获取域中存储的值_对象值

对象：

<%@ page import="com.ailyt.domain.User" %>
<%@ page import="java.util.Date" %><%--
  Created by IntelliJ IDEA.
  User: lihaiyang
  Date: 2022/8/16
  Time: 14:02
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

    <%
        User user = new User();
        user.setName("张三");
        user.setAge(21);
        user.setBirthday(new Date());

        request.setAttribute("u",user);
    %>
    <br><br><br>
    ${u.name}<br><br><br>
    ${u.age}<br><br><br>
    ${u.birthday}<br><br><br>
    ${u.toString()}<br><br><br>

    <hr>

    ${requestScope.get("u")}<br><br><br>
    ${requestScope.u}<br><br><br>
    ${requestScope.u.name}<br><br><br>
    ${requestScope.u.age}<br><br><br>
    ${requestScope.u.birthday}<br><br><br>

    <hr>

    ${requestScope.get("u").name}<br><br><br>
    ${requestScope.get("u").age}<br><br><br>
    ${requestScope.get("u").birthday}<br><br><br>


</body>
</html>