Servlet: Servlet+JDBC应用

Servlet+JDBC应用

　　<1> 在Servlet中可以使用JDBC技术访问数据库，常见功能如下：

　　　　　　查询DB数据，然后生成显示页面，例如：列表显示功能

　　　　　　接收请求参数，然后对DB操作，例如：注册、登录、修改密码等功能

 

　　<2> 为了方便重用和便于维护等目的，经常会采用DAO（Data Access Object）模式对数据库操作进行 独立封装

　　

 

 

　　<3> DAO工厂(工厂模式)

　　　　工厂类：封装了对象的创建细节，为调用者提供符合要求的对象

 

<4> demo01

Dao / UserDao.java

package com.lagou.demo01.dao;

import com.lagou.demo01.model.User;
import com.lagou.demo01.util.DbUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class UserDao {

    public int createUser(User user) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        try {
            // 1.获取连接
            connection = DbUtil.getConnection();
            // 2.准备sql语句
            String sql = "insert into t_user values(null, ?, ?)";
            // 3.获取PrepareStatement类型的引用
            preparedStatement = connection.prepareStatement(sql);
            // 4.向问号所占的位置设置数据
            preparedStatement.setString(1, user.getUserName());
            preparedStatement.setString(2, user.getPassword());
            // 5.执行sql语句
            int row = preparedStatement.executeUpdate();
            return row; // 执行成功
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            // 6.关闭资源
            try {
                DbUtil.closeConnection(connection, preparedStatement);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return 0; // 执行失败
    }
}

 

Model / User.java

package com.lagou.demo01.model;

public class User {
    private int id;
    private String userName;
    private String password;

    public User() {
    }

    public User(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

 

Servlet / RegisterServlet.java

package com.lagou.demo01.servlet;

import com.lagou.demo01.dao.UserDao;
import com.lagou.demo01.model.User;

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.io.PrintWriter;

public class RegisterServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 1.获取请求对象中保存的用户名和密码信息
        String userName = request.getParameter("userName");
        System.out.println("获取到的用户名为：" + userName);
        String password = request.getParameter("password");
        System.out.println("获取到的密码为：" + password);
        // 2.将接受到的用户名和密码信息打包成用户对象交给DAO层进行处理
        User user = new User(userName, password);
        UserDao userDao = new UserDao();
        int res = userDao.createUser(user);
        // 3.将处理结果响应到浏览器
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        if (1 == res) {
            System.out.println("注册成功！");
            writer.write("<h1>注册成功！</h1>");
        } else {
            writer.write("<h1>注册失败！</h1>");
        }
        writer.close();
    }

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

 

Test / DBUtilTest.java

package com.lagou.demo01.test;

import com.lagou.demo01.util.DbUtil;

import java.sql.Connection;
import java.sql.SQLException;

public class DbUtilTest {

    public static void main(String[] args) {

        Connection connection = null;
        try {
            connection = DbUtil.getConnection();
            System.out.println("连接数据库成功！");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            /*try {
                DbUtil.closeConnection(connection);
            } catch (SQLException e) {
                e.printStackTrace();
            }*/
        }
    }
}

 

Util / DBUtil.java

package com.lagou.demo01.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DbUtil {
    private static String jdbcName;   // 用于描述驱动信息
    private static String dbUrl;      // 用于描述URL信息
    private static String dbUserName; // 用户描述用户名信息
    private static String dbPassword; // 用户描述密码信息

    // 进行静态成员的初始化操作
    static {
        jdbcName = "com.mysql.jdbc.Driver";
        dbUrl = "jdbc:mysql://localhost:3306/db_web";
        dbUserName = "root";
        dbPassword = "123456";
        try {
            Class.forName(jdbcName);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取连接
     * @return
     * @throws SQLException
     */
    public static Connection getConnection() throws SQLException {
        Connection con = DriverManager.getConnection(dbUrl, dbUserName, dbPassword);
        return con;
    }

    /**
     * 关闭连接
     * @param con
     * @throws SQLException
     */
    public static void closeConnection(Connection con, PreparedStatement psts) throws SQLException {
        if (null != con) {
            con.close();
        }
        if (null != psts) {
            psts.close();
        }
    }
}

 

Web / index.jsp

<%--
  Created by IntelliJ IDEA.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  $END$
  </body>
</html>

 

Web / register.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>实现简单的注册功能</title>
</head>
<body>
<form action="register" method="post">
    用户名：<input type="text" name="userName"/><br/>
    密&nbsp;&nbsp;&nbsp;&nbsp;码：<input type="text" name="password"/><br/>
    <input type="submit" value="注册"/>
</form>
</body>
</html>