JDBC基础----用户登录案例

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概念：JDBC（java database connectivity），就是一种API，提供了规范，定义了接口和类，用于方便操作不同数据库

掌握JDBC的基础就在于四个类

1. DriverManager                        驱动类2. Connection                           连接类3. PreparedStatement                    语句类4. ResultSet                            结果类

驱动类：因为市面上有很多的数据库产品，那么相应的就会有许多的驱动，这些都是由数据库厂商提供的
连接类：这是数据库与程序之间的桥梁
语句类：用于编写各种SQL语句来操作数据库
结果类：自然是用来接收返回的数据的

其中重点的方法：

//1. 加载mysql驱动类Class.forName("com.mysql.jdbc.Driver");//2. 获得连接对象/**'jdbc:mysql://'   为连接mysql固定写法'localhost:3306/' 表示为连接本机IP的mysql的默认3306端口'test'            要连接的数据库名                 */String url = "jdbc:mysql://localhost:3306/test"; String user = "abc";String password = "123";Connection conn = DriverManager.getConnection(url, user, password);//3. 准备SQL语句/**sql中的*号可以使用setString()方法被替换成条件被执行*/String sql = "SELECT * FROM user WHERE name = ? AND pwd = ?";PreparedStatement ps = conn.prepareStatement(sql);ps.setString(1, name);ps.setString(2, pwd);//4. 处理结果ResultSet rs = ps.executeQuery(); //执行查询语句，接收返回结果while(rs.next()) { 一笔一笔循环取值，若没有值，返回false    String s = rs.getString(1);  //取出当前行中第一个字段     Int i = rs.getInt(2);  //取出当前行中第二个字段    ...}//5. 别忘了关闭资源rs.close();ps.close();conn.close();

贴上代码

package util;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.ResourceBundle;public class DBUtils {    private static String driveClass;    private static String url;    private static String user;    private static String password;    static {        url = "jdbc:mysql:///test?useSSL=false";        user = "abc";        password = "123";        try {            Class.forName("com.mysql.jdbc.Driver");        } catch(ClassNotFoundException e) {            e.printStackTrace();        }    }    //得到连接    public static Connection getConnection() throws SQLException{        return DriverManager.getConnection(url, user, password);        }    //关闭资源    public static void closeAll(ResultSet rs, Statement stmt, Connection conn) {        if(rs != null) {            try {                rs.close();            } catch(SQLException e) {                e.printStackTrace();            }        }        if(stmt != null) {            try {                stmt.close();            } catch(SQLException e) {                e.printStackTrace();            }        }        if(conn != null) {            try {                conn.close();            } catch(SQLException e) {                e.printStackTrace();            }        }    }}

package service;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;import entity.User;import util.DBUtils;public class DoLogin {    public User findUser(String name, String password) {        Connection conn = null;        PreparedStatement ps = null;        ResultSet rs = null;        User u = null;        try {            conn = DBUtils.getConnection();            String sql = "SELECT * FROM user WHERE name = ? AND pwd = ?";            ps = conn.prepareStatement(sql);            ps.setString(1, name);            ps.setString(2,pwd);            rs = ps.executeQuery();            if(rs.next()) {                u = new User();                u.setName(rs.getString(1));                u.setPassword(rs.getString(2));            }        } catch(SQLException e) {            e.printStackTrace();        } finally {            DBUtils.closeAll(rs, ps, conn);        }        return u;    }}

package client;import java.util.Scanner;import entity.User;import service.DoLogin;public class Login {    public static void main(String[] args) {        // TODO Auto-generated method stub        System.out.println("请输入用户名");        Scanner scan = new Scanner(System.in);        String name = scan.nextLine();        System.out.println("请输入密码");        String password = scan.nextLine();        DoLogin dl = new DoLogin();        User u = dl.findUser(name, password);        if(u != null) {            System.out.println("欢迎登陆" + " " + u.getName());        } else {            System.out.println("用户名或者密码有误");        }    }}

package entity;public class User {    private String name;    private String password;    public User() {    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public String getPassword() {        return password;    }    public void setPassword(String password) {        this.password = password;    }    @Override    public String toString() {        return "User [name=" + name + ", password=" + password + "]";    }}

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