MVC腳手架（一）之javabean+jsp+servlet+jdbc

時間 2019-11-13

標籤 mvc 腳手架 javabean+jsp+servlet+jdbc javabean jsp servlet jdbc 欄目 Java 简体版

原文原文鏈接

前言javascript

這是一篇最第一版本的mvc設計模式的demo。弄明白這其中的邏輯，對後面掌握ssh,ssm等框架大有裨益。css

另外計算機系的同窗們也要爲畢設作準備了，但願能夠幫大家邁出本身作畢設的第一步（微笑臉.jgp）。html

特別提示：不要被文章篇幅嚇到（再次微笑臉.jpg）。文中貼出了部分過程圖片便於你們理解，而且代碼部分未摺疊，拿來即用！java

補充：因爲部分同窗在根聽說明搭建demo的過程當中會遇到一些問題，因此我把代碼在個人github上放了一份。你們能夠先下載再看下面的搭建過程，也能夠先本身動手搭建，遇到問題再對比異同，隨意咯~mysql

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

使用方法：github

　　1.新建一個名爲MyServlet的Dynamic Web Project，不論你使用的是idea，eclipse，仍是STS，均可以web

　　2.將github中的代碼下載sql

　　3.分別用從github中下載的代碼裏面的src目錄和webContent目錄，替換你新建的MyServlet項目中的src目錄和webContent目錄數據庫

　　4.修改helper.DbHelper中鏈接數據庫的用戶名和密碼

　　5.使用tomcat啓動項目，並經過 http://localhost:8080/MyServlet/list 訪問項目

下面進入詳細解說環節：

本篇採用javabean+jsp+servlet+jdbc，附源碼。

M = JavaBean：用於傳遞數據，擁有與數據相關的邏輯處理
V = JSP：從Model接收數據並生成HTML
C = Servlet：接收HTTP請求並控制Model和View

環境：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. 新建數據表

在mysql中新建一個名爲my-db的數據庫，並在其中新建一個user數據表，包含三個字段：id，name，age，如圖

ps：在這裏給各位同窗安利一個叫作Navicat的數據庫操做軟件，功能十分強大。有了它，能夠大幅減小在cmd中輸入creat table...之類的命令數量，推薦Navicat Premium。

注意：將id設爲自動遞增，不然後面新增會出錯。id設爲自增，新增時就只需關注user的其它屬性。

二. 新建web項目

1. eclipse新建一個名爲MyServlet的Dynamic Web Project

　　修改class的默認輸出目錄爲：WebContent/WEB-INF/classes

　　勾選自動生成web.xml

　　生成的項目在java EE透視圖中的結構以下，

2. 將鏈接mysql的驅動jar包（mysql-connector-java-5.1.7-bin.jar）copy到WEB-INF下的lib目錄下

3. 新建4個包，common存放實體類(User)，dao存放數據庫操做類(UserDao)，servlet存放控制類(addServlet,updateServlet,deleteServlet,listServlet)，helper存放開發幫助類(這裏是數據庫操做幫助類，封裝了數據庫鏈接部分代碼，避免大量重複代碼)

4. 新建類(最愉快的搬磚環節 -.-)，java類放在對應包中，jsp頁面放在WebContent目錄下，替換web.xml中內容，結構如圖

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 {
    /**
     * 查詢全部用戶信息
     * @return
     */
     public List<User> getAllUser(){  
            List<User> list = new ArrayList<User>();  
            Connection conn = DbHelper.getConnection();//鏈接數據庫
            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;  
        }
     
        /**
         * 添加用戶
         * @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;
        }
        
        /**
         * 修改用戶信息
         * @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;
        }
        
        /**
         * 刪除用戶
         * @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;
        }
        
        /**
         * 根據ID進行查詢用戶
         * @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";  //數據庫地址
    private static String userName = "root";  //數據庫用戶名
    private static String passWord = "123456";  //數據庫密碼
    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) {  //測試數據庫是否連通
        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();//建立user對象
        user.setName(name);
        user.setAge(age);
        UserDao dao = new UserDao();
        dao.addUser(user);//添加到數據庫中
        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"); // 刪除數據的ID，根據ID刪除
        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")
//上面註釋的是WebServlet3.0的使用方式，經過這樣的註解，不須要配置web.xml也可運行程序
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 {
    /**
     * 查詢到選中ID的值所對應的數據
     */
    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);
    }

    /**
     * 根據此ID對數據的值進行修改
     */
    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頁面放在WebContent目錄下

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>新增用戶</title>
<script type="text/javascript">  
    function check(form) {  
        with (form) {  
            if (name.value == "") {  
                alert("用戶名不能爲空");  
                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>添加用戶信息</h2>  
                <hr>  
            </td>  
        </tr>  
        <tr>  
            <td align="right">用戶名：</td>  
            <td><input type="text" name="name"></td>  
        </tr>  
        <tr>  
            <td align="right">年齡：</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>全部用戶</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">添加新用戶</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>全部用戶信息</h2>  
            </td>  
        </tr>  
        <tr align="center" bgcolor="#e1ffc1">  
            <td><b>ID</b></td>  
            <td><b>姓名</b></td>  
            <td><b>年齡</b></td>  
            <td colspan="2"><b>操做</b></td>  
        </tr>  
        <%  
            // 獲取用戶信息集合  
            List<User> list = (List<User>) request.getAttribute("userInfoList");  
            // 判斷是否有數據
            if (list == null || list.size() < 1) {  
        %>
                <tr bgcolor="white"><td colspan="5" ><h4 align="center">沒有數據</h4></td></tr>
        <%
            } else {  
                // 遍歷用戶集合中的數據  
                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()%>">刪除</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>修改用戶信息頁面</title>
</head>
<body>
    <div>
        <table>
            <thead><tr><td><h1>修改用戶信息</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>

替換web.xml中內容

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的註冊名稱，自定義。每一個servlet的name不同 -->
        <servlet-name>listServ</servlet-name>
        <!-- servlet的完整類名： 包名+類名；若是ctrl+鼠標左擊能 點開，說明成功-->
        <servlet-class>servlet.ListServlet</servlet-class>
    </servlet>
    <!-- servlet的映射配置 -->
    <servlet-mapping>
        <!-- servlet的註冊名稱，必定要和上面的內部名稱保持一致！！ -->
        <servlet-name>listServ</servlet-name>
        <!-- servlet的對外訪問路徑（訪問servlet的名稱） -->
        <url-pattern>/list</url-pattern>
    </servlet-mapping>
    <!-- ps:同一個servlet能夠配置多個servlet-mapping，舉個栗子 -->
    <servlet-mapping>
        <!-- 仍是上面的那個servlet -->
        <servlet-name>listServ</servlet-name>
        <!-- 除了/ListServlet,又配置了一個list2,經過這兩個路徑均可訪問listServ這個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>