在MVC中应用表达式

定义VO类

package com.ming.vo;

// vo类
public class Dept {
    private int deptno;
    private String dname;
    private String ioc;

    public int getDeptno() {
        return deptno;
    }

    public String getDname() {
        return dname;
    }

    public String getIoc() {
        return ioc;
    }

    public void setDeptno(int deptno) {
        this.deptno = deptno;
    }

    public void setDname(String dname) {
        this.dname = dname;
    }

    public void setIoc(String ioc) {
        this.ioc = ioc;
    }
}

定义servlet

package com.ming.servlet;


import com.ming.vo.Dept;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class ElListServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        List<Dept> all = new ArrayList<Dept>();
        Dept dept = null;
        dept = new Dept();
        dept.setIoc("ming");
        dept.setDname("ming");
        dept.setDeptno(2);
        // 数组中加入
        all.add(dept);
        // 再次进行引用, 由数组持有该对象的引用
        dept = new Dept();
        dept.setDname("ming");
        dept.setDeptno(3);
        dept.setIoc("xiao");
        all.add(dept);
        // 属性中传入
        req.setAttribute("alldept", all);
        // 服务端跳转
        req.getRequestDispatcher("dept_list.jsp").forward(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

书写jsp 接收传值

<%@ page import="java.util.List" %>
<%@ page import="java.util.Iterator" %>
<%@ page isELIgnored="false"%>
<%@ page import="com.ming.vo.Dept" %><%--
  Created by IntelliJ IDEA.
  User: ming
  Date: 19-3-18
  Time: 下午11:48
  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>
<%
   List all = (List)request.getAttribute("alldept");
   Iterator iterator = all.iterator();
   while(iterator.hasNext()){
       pageContext.setAttribute("dept", (Dept)iterator.next());
       %>
            ${dept.deptno}
            ${dept.dname}
            ${dept.ioc}
        <%
   }

%>

</body>
</html>

配置文件如下

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
  <display-name>Archetype Created Web Application</display-name>
  <servlet>
    <servlet-name>ElistServlet</servlet-name>
    <servlet-class>com.ming.servlet.ElListServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>ElistServlet</servlet-name>
    <url-pattern>/ElistServlet</url-pattern>
  </servlet-mapping>
</web-app>

解决jsp不显示

增加了个maven依赖

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>fgdfbg</groupId>
  <artifactId>gfnhfgnfj</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>gfnhfgnfj Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.15</version>
    </dependency>
    <dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.4</version>
    </dependency>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.0</version>
      <scope>provided</scope>
    </dependency>
    <dependency>
      <groupId>tomcat</groupId>
      <artifactId>servlet</artifactId>
      <version>4.0.6</version>
    </dependency>
  </dependencies>

  <build>
    <finalName>gfnhfgnfj</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>