Java Web之EL

时间：2024-09-07 19:33:26

Java Web之EL

<%--

  Created by IntelliJ IDEA.

  User: Vae

  Date: 2019/1/2

  Time: 12:19

  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>

<p>许嵩许嵩</p>

<%

    //JSP的四大作用域

    pageContext.setAttribute("msg","pageContext");

    request.setAttribute("msg","request");

    session.setAttribute("msg","session");

    application.setAttribute("msg","application");

%>

<h3>获取每一个作用域中的值</h3>

pageContext:<%=pageContext.getAttribute("msg")%><br>

request:<%=request.getAttribute("msg")%><br>

session:<%=session.getAttribute("msg")%><br>

application:<%=application.getAttribute("msg")%><br>

<hr>

<h3>pageContext的findAttribute方法(只有pageContext才有)</h3>

<%=pageContext.findAttribute("msg")%><br>

<%=pageContext.findAttribute("msg")==null?"":pageContext.findAttribute("msg")%><br>

${msg}<br>

</body>

</html>

Java Web之EL

EL  ${msg} 是从作用域从小往大找的，也可以设置为只从某个作用域查询

<!--EL的四大作用域对象-->

${pageScope.msg}<br>

${requestScope.msg}<br>

${sessionScope.msg}<br>

${applicationScope.msg}<br>

EL获取Java Bean数据

新建一个包，新建一个Servlet类和Person类

package main.com.vae.EL;

import lombok.Getter;

import lombok.Setter;

import java.util.Arrays;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

@Setter@Getter

public class Person {

    private String name="许嵩";

    private Integer age=32;

    private String[] hobbys={"音乐","遛狗","D"};

    private List<String> list=Arrays.asList("list1","list2");

    private Map<String,Object> map=new HashMap<String,Object>(){

        {

            this.put("6","青年晚报");

            this.put("7","寻宝游戏");

            this.put("www.vae.com","Vae+");

        }

    };

}
package main.com.vae.EL;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet("/el")

public class ELServlet extends HttpServlet {

    @Override

    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        Person person=new Person();

        req.setAttribute("person",person);

        req.getRequestDispatcher("/jspDemo/EL/el.jsp").forward(req,resp);

    }

}

再建一个jsp叫el

Java Web之EL

<%--

  Created by IntelliJ IDEA.

  User: Vae

  Date: 2019/1/9

  Time: 13:41

  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>

<h3>Person对象的信息</h3><br>

name:${person.name}-->${person.getName()}-->${person["name"]}<br>

age:${person.age}<br>

hobbys:${person.hobbys[0]}-->${person.hobbys[1]}<br>

list:${person.list[0]}-->${person.list[1]}<br>

map:${person.map["6"]}-->${person.map["www.vae.com"]}<br>

</body>

</html>

结果：

Java Web之EL

像map里面的 www.vae.com 这个显然就不能使用 person.map.www.vae.com来调用了，不认识的，只能使用[""]来调用了。

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