诺禾：在jsp里面如何不写java代码展示数据(EL表达式的使用)

Z时代
2024-01-10
分类：综合

在jsp里面如何不写java代码展示数据(EL表达式的使用)

EL如果没有获取到值会显示空字符串而不是显示null
在jsp里面如何不写java代码展示数据(EL表达式的使用)

在jsp里面如何不写java代码展示数据(EL表达式的使用)

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>el的隐式对象</title>
</head>
<body>
${pageContext.request}<br>
<h4>在jsp页面动态获取虚拟目录</h4>
${pageContext.request.contextPath}<br>
</body>
</html>

package cn.itcast.domain;

import java.text.SimpleDateFormat;
import java.util.Date;

public class User {
   private String name;
   private int age;
   private Date birthday;
   /*
   * 逻辑视图
   */
   public String getBirStr() {
       if(birthday!=null) {
           //1.格式化日期对象
           SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
           //2.返回字符串即可
           return sdf.format(birthday);
       }else {
           return "";
       }
   }


   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }
   public int getAge() {
       return age;
   }
   public void setAge(int age) {
       this.age = age;
   }
   public Date getBirthday() {
       return birthday;
   }
   public void setBirthday(Date birthday) {
       this.birthday = birthday;
   }

}

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>el2获取域中的数据</title>
</head>
<body>
   <%
       //在域中存储数据
       request.setAttribute("name", "张三");
       session.setAttribute("age", "23");

   %>
   <h3>el获取值</h3>
   ${requestScope.name};
   ${sessionScope.age};
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="cn.itcast.domain.User" %>
<%@ page import="java.util.*" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
   <%
       User user=new User();
       user.setName("张三");
       user.setAge(23);
       user.setBirthday(new Date());
       request.setAttribute("u", user);

       List list=new ArrayList();
       list.add("aaa");
       list.add("bbb");
       list.add(user);

       request.setAttribute("list", list);

       Map map=new HashMap();
       map.put("sname","李四");
       map.put("gender","男");
       map.put("user",user);


   %>
<h3>el获取对象中的值</h3>
${requestScope.u };<br>
<%--
通过的是对象的属性来获取
setter或getter方法，去掉set或get,再将剩余部分，首字母变为小写。
setName-->Name-->name
--%>
${requestScope.u.name };<br>
${requestScope.u.age};<br>
${requestScope.u.birthday };<br>
${requestScope.u.birthday.month };<br>
${u.birStr}<br>
<h3>el获取List的值</h3>
${list};<br>
${list[0]};<br>
${list[1]};<br>
${list[2].name};<br>
<h3>el获取Map的值</h3>
${map.gender};<br>
${map["gender"]};<br>

${map.user.name};<br>