MVC脚手架（一）之javabean+jsp+servlet+jdbc

前言

这是一篇最初版本的mvc设计模式的demo。弄明白这其中的逻辑，对后面掌握ssh,ssm等框架大有裨益。

另外计算机系的同学们也要为毕设做准备了，希望可以帮你们迈出自己做毕设的第一步（微笑脸.jgp）。

特别提示：不要被文章篇幅吓到（再次微笑脸.jpg）。文中贴出了部分过程图片便于大家理解，并且代码部分未折叠，拿来即用！

补充：由于部分同学在根据说明搭建demo的过程中会遇到一些问题，所以我把代码在我的github上放了一份。大家可以先下载再看下面的搭建过程，也可以先自己动手搭建，遇到问题再对比异同，随意咯~

github地址：https://github.com/QubingHuo/javabean-jsp-servlet-jdbc

使用方法：

　　1.新建一个名为MyServlet的Dynamic Web Project，不论你使用的是idea，eclipse，还是STS，都可以

　　2.将github中的代码下载

　　3.分别用从github中下载的代码里面的src目录和webContent目录，替换你新建的MyServlet项目中的src目录和webContent目录

　　4.修改helper.DbHelper中连接数据库的用户名和密码

　　5.使用tomcat启动项目，并通过 http://localhost:8080/MyServlet/list 访问项目

下面进入详细解说环节：

本篇采用javabean+jsp+servlet+jdbc，附源码。

M = JavaBean：用于传递数据，拥有与数据相关的逻辑处理
V = JSP：从Model接收数据并生成HTML
C = Servlet：接收HTTP请求并控制Model和View

环境：win7 64位，jdk1.8，tomcat7，mysql 5.5

工具：eclipse，Navicat premium

jar包：mysql-connector-java-5.1.13-bin.jar

一. 新建数据表

在mysql中新建一个名为my-db的数据库，并在其中新建一个user数据表，包含三个字段：id，name，age，如图

ps：在这里给各位同学安利一个叫做Navicat的数据库操作软件，功能十分强大。有了它，可以大幅减少在cmd中输入creat table...之类的命令数量，推荐Navicat Premium。

注意：将id设为自动递增，否则后面新增会出错。id设为自增，新增时就只需关注user的其它属性。

二. 新建web项目

1. eclipse新建一个名为MyServlet的Dynamic Web Project

　　修改class的默认输出目录为：WebContent/WEB-INF/classes

　　勾选自动生成web.xml

　　生成的项目在java EE透视图中的结构如下，

2. 将连接mysql的驱动jar包（mysql-connector-java-5.1.7-bin.jar）copy到WEB-INF下的lib目录下

3. 新建4个包，common存放实体类(User)，dao存放数据库操作类(UserDao)，servlet存放控制类(addServlet,updateServlet,deleteServlet,listServlet)，helper存放开发帮助类(这里是数据库操作帮助类，封装了数据库连接部分代码，避免大量重复代码)

4. 新建类(最愉快的搬砖环节 -.-)，java类放在对应包中，jsp页面放在WebContent目录下，替换web.xml中内容，结构如图

User.java

package common;

public class User {
    private Integer id;
    private String name;
    private Integer age;
    
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
}

UserDao.java

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import common.User;
import helper.DbHelper;

public class UserDao {
    /**
     * 查询所有用户信息
     * @return
     */
     public List<User> getAllUser(){  
            List<User> list = new ArrayList<User>();  
            Connection conn = DbHelper.getConnection();//连接数据库
            String sql  = "select * from user";  
            try {
                PreparedStatement pst = conn.prepareStatement(sql);
                ResultSet rst = pst.executeQuery();
                while (rst.next()) {
                    User user = new User();
                    user.setId(rst.getInt("id"));  
                    user.setName(rst.getString("name"));
                    user.setAge(rst.getInt("age"));
                    list.add(user);
                }
                rst.close();  
                pst.close();  
            } catch (SQLException e) {
                e.printStackTrace();  
            }
            return list;  
        }
     
        /**
         * 添加用户
         * @param user
         * @return
         */
        public boolean addUser(User user){ 
            String sql = "INSERT INTO `user`(`name`,`age`) VALUES (?,?)";  
            Connection conn = DbHelper.getConnection();
            try {
                PreparedStatement pst = conn.prepareStatement(sql);
                pst.setString(1, user.getName());
                pst.setInt(2, user.getAge());
                int count = pst.executeUpdate();
                pst.close();
                return count>0?true:false; 
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return false;
        }
        
        /**
         * 修改用户信息
         * @param user
         * @return
         */
        public boolean updateUser(User user){  
            String sql = "UPDATE `user` SET `name`=?,`age`=? WHERE `id` = ?"; 
            Connection conn = DbHelper.getConnection();
            try {
                PreparedStatement pst = conn.prepareStatement(sql);
                pst.setString(1, user.getName());
                pst.setInt(2, user.getAge());
                pst.setInt(3, user.getId());  
                int count = pst.executeUpdate();
                pst.close(); 
                return count>0?true:false;  
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return false;
        }
        
        /**
         * 删除用户
         * @param id
         * @return
         */
        public boolean deleteUser(int id){  
            String sql = "delete from user where id = ?"; 
            Connection conn = DbHelper.getConnection();
            try {
                PreparedStatement pst = conn.prepareStatement(sql);
                pst.setInt(1, id);
                int count = pst.executeUpdate();
                pst.close();
                return count>0?true:false;  
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return false;
        }
        
        /**
         * 根据ID进行查询用户
         * @param id
         * @return
         */
        public User selectUserById(int id){  
            Connection conn = DbHelper.getConnection();
            String sql  = "select * from user where id = "+id;
            User user = null;
            try {
                PreparedStatement pst = conn.prepareStatement(sql);
                ResultSet rst = pst.executeQuery();
                while (rst.next()) {
                    user = new User();
                    user.setId(rst.getInt("id"));
                    user.setName(rst.getString("name"));
                    user.setAge(rst.getInt("age"));
                }
                rst.close();
                pst.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return user;  
        }
}

DbHelper.java

package helper;

import java.sql.Connection;
import java.sql.DriverManager;

public class DbHelper {
    private static String url = "jdbc:mysql://localhost:3306/my-db";  //数据库地址
    private static String userName = "root";  //数据库用户名
    private static String passWord = "123456";  //数据库密码
    private static Connection conn = null;
    
    private DbHelper(){
        
    }
    
    public static Connection getConnection(){
        if(null == conn){
            try {
                Class.forName("com.mysql.jdbc.Driver");
                conn = DriverManager.getConnection(url, userName, passWord);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        return conn;
    }
    
    public static void main(String[] args) {  //测试数据库是否连通
        System.out.println(getConnection());
    }
}

AddServlet.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import common.User;
import dao.UserDao;

public class AddServlet extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String name = req.getParameter("name");
        Integer age = Integer.valueOf(req.getParameter("age"));
        User user = new User();//创建user对象
        user.setName(name);
        user.setAge(age);
        UserDao dao = new UserDao();
        dao.addUser(user);//添加到数据库中
        req.getRequestDispatcher("list").forward(req, resp);
    }
}

DeleteServlet.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.UserDao;

public class DeleteServlet extends HttpServlet{
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String idStr = req.getParameter("id"); // 删除数据的ID，根据ID删除
        if (idStr != null && !idStr.equals("")) {
            int id = Integer.valueOf(idStr);
            UserDao dao = new UserDao();
            dao.deleteUser(id);
        }
        req.getRequestDispatcher("list").forward(req, resp);
    }
}

ListServlet.java

package servlet;

import java.io.IOException;
import java.util.List;

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 common.User;
import dao.UserDao;

//@WebServlet("/list")
//上面注释的是WebServlet3.0的使用方式，通过这样的注解，不需要配置web.xml也可运行程序
public class ListServlet extends HttpServlet {

    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        UserDao dao = new UserDao();
        List<User> list = dao.getAllUser();
        req.setAttribute("userInfoList", list);
        req.getRequestDispatcher("list.jsp").forward(req, resp);
        
    }

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

UpdateServlet.java

package servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import common.User;
import dao.UserDao;

public class UpdateServlet extends HttpServlet {
    /**
     * 查询到选中ID的值所对应的数据
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
        String idStr = req.getParameter("id");
        if (idStr != null && !idStr.equals("")) {
            int id = Integer.valueOf(idStr);
            UserDao dao = new UserDao();
            User user = dao.selectUserById(id);
            req.setAttribute("user", user);
        }
        req.getRequestDispatcher("update.jsp").forward(req, resp);
    }

    /**
     * 根据此ID对数据的值进行修改
     */
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
        String idStr = req.getParameter("id");
        if (idStr != null && !idStr.equals("")) {
            int id = Integer.valueOf(idStr);
            String name = req.getParameter("name");
            Integer age = Integer.valueOf(req.getParameter("age"));
            User user = new User();
            user.setId(id);
            user.setName(name);
            user.setAge(age);
            UserDao dao = new UserDao();
            dao.updateUser(user);
        }
        req.getRequestDispatcher("list").forward(req, resp);
    }
}

jsp页面放在WebContent目录下

add.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>新增用户</title>
<script type="text/javascript">  
    function check(form) {  
        with (form) {  
            if (name.value == "") {  
                alert("用户名不能为空");  
                return false;  
            }  
        }  
    }  
</script>
</head>
<body>
<form action="add" method="post" onsubmit="check(this)">  
    <table align="center" width="450">  
        <tr>  
            <td align="center" colspan="2">  
                <h2>添加用户信息</h2>  
                <hr>  
            </td>  
        </tr>  
        <tr>  
            <td align="right">用户名：</td>  
            <td><input type="text" name="name"></td>  
        </tr>  
        <tr>  
            <td align="right">年龄：</td>  
            <td><input type="text" name="age"></td>  
        </tr>  
        <tr>  
            <td align="center" colspan="2">
                <input type="submit" value="添　加">  
            </td>  
        </tr>  
    </table>  
</form>  
</body>
</html>

list.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"  
    pageEncoding="utf-8"%>  
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  
<%@page import="java.util.List"%>  
<%@page import="common.User"%>  
<html>  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">  
<title>所有用户</title>  
<style type="text/css">  
td {  
    font-size: 12px;  
}  
h2 {  
    margin: 0px  
}  
</style>  
<script type="text/javascript">  
   
</script>  
</head>  
<body>  
    <h2 align="center">  
        <a href="add.jsp">添加新用户</a>  
    </h2> 
    <br>
    <table align="center" width="450" border="1" height="180"  
        bordercolor="white" bgcolor="black" cellpadding="1" cellspacing="1">  
        <tr bgcolor="white">  
            <td align="center" colspan="7">  
                <h2>所有用户信息</h2>  
            </td>  
        </tr>  
        <tr align="center" bgcolor="#e1ffc1">  
            <td><b>ID</b></td>  
            <td><b>姓名</b></td>  
            <td><b>年龄</b></td>  
            <td colspan="2"><b>操作</b></td>  
        </tr>  
        <%  
            // 获取用户信息集合  
            List<User> list = (List<User>) request.getAttribute("userInfoList");  
            // 判断是否有数据
            if (list == null || list.size() < 1) {  
        %>
                <tr bgcolor="white"><td colspan="5" ><h4 align="center">没有数据</h4></td></tr>
        <%
            } else {  
                // 遍历用户集合中的数据  
                for (User user : list) {  
        %>  
        <tr align="center"  bgcolor="white">  
            <td><%=user.getId()%></td>  
            <td><%=user.getName()%></td>  
            <td><%=user.getAge()%></td>  
            <td >  
               <a href="update?id=<%=user.getId()%>">修改</a>
                 
            </td>  
            <td>  
                <a href="delete?id=<%=user.getId()%>">删除</a>  
            </td>  
        </tr>  
        <%  
            }  
            }  
        %>  
    </table>  
</body>  
</html>

update.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@page import="common.User"%> 
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>修改用户信息页面</title>
</head>
<body>
    <div>
        <table>
            <thead><tr><td><h1>修改用户信息</h1></td></tr></thead>
            <tbody>
                <form action="update" method="post">
                <tr>
                    <td>ID：</td>
                    <td><input type="text" name="id" value="${user.id}"
                        readonly="readonly" /></td>
                </tr>
                <tr>
                    <td>name：</td>
                    <td><input type="text" name="name" value="${user.name}" /></td>
                </tr>
                <tr>
                    <td>age：</td>
                    <td><input type="text" name="age" value="${user.age}" /></td>
                </tr>
                <tr>
                    <td><input class="btn" type="submit" value="提交" /> <input
                        class="btn" type="reset" value="重置" /></td>
                </tr>
            </tbody>
            </form>
        </table>
    </div>
</body>
</html>

替换web.xml中内容

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>MyServlet</display-name>
     <servlet>
        <!-- servlet的注册名称，自定义。每个servlet的name不一样 -->
        <servlet-name>listServ</servlet-name>
        <!-- servlet的完整类名： 包名+类名；如果ctrl+鼠标左击能 点开，说明成功-->
        <servlet-class>servlet.ListServlet</servlet-class>
    </servlet>
    <!-- servlet的映射配置 -->
    <servlet-mapping>
        <!-- servlet的注册名称，一定要和上面的内部名称保持一致！！ -->
        <servlet-name>listServ</servlet-name>
        <!-- servlet的对外访问路径（访问servlet的名称） -->
        <url-pattern>/list</url-pattern>
    </servlet-mapping>
    <!-- ps:同一个servlet可以配置多个servlet-mapping，举个栗子 -->
    <servlet-mapping>
        <!-- 还是上面的那个servlet -->
        <servlet-name>listServ</servlet-name>
        <!-- 除了/ListServlet,又配置了一个list2,通过这两个路径都可访问listServ这个servlet -->
        <url-pattern>/list2</url-pattern>
    </servlet-mapping>
    
     <servlet>
        <servlet-name>addServ</servlet-name>
        <servlet-class>servlet.AddServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>addServ</servlet-name>
        <url-pattern>/add</url-pattern>
    </servlet-mapping>
    
     <servlet>
        <servlet-name>updateServ</servlet-name>
        <servlet-class>servlet.UpdateServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>updateServ</servlet-name>
        <url-pattern>/update</url-pattern>
    </servlet-mapping>
    
     <servlet>
        <servlet-name>delServ</servlet-name>
        <servlet-class>servlet.DeleteServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>delServ</servlet-name>
        <url-pattern>/delete</url-pattern>
    </servlet-mapping>
</web-app>