EL表达式
*Expression Language 表达式语言，用于简化jsp页面中的Java语言
*主要功能:获取数据
*语法:{brands}意思是获取域中存储的key为brands的数据
*javaWeb中的四大域对象（el表达式会在这四个域中寻找，直到找到为止）
1.page：当前页面有效
2.request：当前的请求有效
3.session：当前的会话有效
4.application：当前应用有效
1.项目大致结构
准备三个类
1.pojo包下的 实体类 brand
2.web包下的servlet类 servlet-el
3.webapp包下的jsp文件 el-demo
1.pojo包下的 实体类 brand
package com.ithema.pojo;
/*
在实体类中，基本数据类型，建议使用其对应的包装类
*/
public class Brand {
//id主键
private Integer id;
//品牌名称
private String brandName;
//企业名称
private String companyName;
//排序字段
private Integer ordered;
//描述信息
private String description;
//状态 0：禁用 1：启用
private Integer status;
public Brand(Integer id, String brandName, String companyName, Integer ordered, String description,
Integer status) {
super();
this.id = id;
this.brandName = brandName;
this.companyName = companyName;
this.ordered = ordered;
this.description = description;
this.status = status;
}
public Brand() {
}
@Override
public String toString() {
return "Brand [id=" + id + ", brandName=" + brandName + ", companyName=" + companyName + ", ordered=" + ordered
+ ", description=" + description + ", status=" + status + "]";
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getBrandName() {
return brandName;
}
public void setBrandName(String brandName) {
this.brandName = brandName;
}
public String getCompanyName() {
return companyName;
}
public void setCompanyName(String companyName) {
this.companyName = companyName;
}
public Integer getOrdered() {
return ordered;
}
public void setOrdered(Integer ordered) {
this.ordered = ordered;
}
public String getDescription() {
return description;
}
public void getDescription(String description) {
this.description = description;
}
public Integer getStatus() {
return status;
}
public void setStatus(Integer status) {
this.status = status;
}
}2.web包下的servlet类 servlet-el
package com.ithema.web;
import com.ithema.pojo.Brand;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
@WebServlet("/demo1")
public class Servlet_el extends HttpServlet {
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.准备数据 现在是list集合，以后是数据库
List<Brand> brands= new ArrayList<Brand>();
brands.add(new Brand(1,"小米公司","小米科技有限公司",100,"为发烧而生",1));
//2.储存带request域中进行转发
request.setAttribute("brands",brands);
//3.进行请求转发
request.getRequestDispatcher("el-demo.jsp").forward(request,response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}
}
3.webapp包下的jsp文件 el-demo.jsp
<%--
Created by IntelliJ IDEA.
User: HP
Date: 2022/8/20
Time: 15:07
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>el表达式</title>
</head>
<body>
${brands}
</body>
</html>
4.浏览器中的效果
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