Java-JDBC详解

//注册与给定的驱动程序 DriverManager
static void registerDriver(Driver driver) ;
//写代码使用 
Class.forName("com.mysql.jdbc.Driver");

//获取数据库连接对象Connection
Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/db3","root","root");

public static void main(String[]args)throwsException{
  //1.导入驱动jar包
  //2.注册驱动
  Class.forName("com.mysql.jdbc.Driver");
  //3.获取数据库连接对象Connection
  Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/db3","root","root");
  //4.定义SQL
  Stringsql="update emp set salary=8001 WHERE id=1001;";
  //5.执行SQL语句对象Statement
  Statementstmt=conn.createStatement();
  //6.执行SQL，接收返回结果
  intcount=stmt.executeUpdate(sql);
  //7.处理结果
  System.out.println(count);
  //8.释放资源
  stmt.close();
  conn.close();
}

import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;
/**
 * JDBC工具类
 */
public class JDBCUtils {
    private static String url;
    private static String user;
    private static String password;
    private static String driver;
    /**
     * 文件的读取，只需要读取一次即可拿到这些值。使用静态代码块
     */
    static{
        //读取资源文件，获取值。
        try {
            //1. 创建Properties集合类。
            Properties pro = new Properties();
            //获取src路径下的文件的方式--->ClassLoader 类加载器
            ClassLoader classLoader = JDBCUtils.class.getClassLoader();
            URL res  = classLoader.getResource("jdbc.properties");
            String path = res.getPath();
            //2. 加载文件
            pro.load(new FileReader(path));
            //3. 获取数据，赋值
            url = pro.getProperty("url");
            user = pro.getProperty("user");
            password = pro.getProperty("password");
            driver = pro.getProperty("driver");
            //4. 注册驱动
            Class.forName(driver);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    /**
     * 获取连接
     * @return 连接对象
     */
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, user, password);
    }
    /**
     * 释放资源
     * @param stmt
     * @param conn
     */
    public static void close(Statement stmt,Connection conn){
        if( stmt != null){
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if( conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     * 释放资源
     * @param stmt
     * @param conn
     */
    public static void close(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();
            }
        }
    }
}

public class DemoLogin {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入账号：");
        String userName = sc.nextLine();
        System.out.println("请输入密码：");
        String password = sc.nextLine();
        boolean flag = new DemoLogin().login2(userName, password);
        if (flag) {
            System.out.println("登录成功！");
        } else {
            System.out.println("账号或密码错误！");
        }
    }
    public boolean login(String name, String password) {
        //账号密码正确性校验
        if (name == null || password == null) {
            return false;
        }
        Connection conn = null;
        Statement statement = null;
        ResultSet resultSet = null;
        try {
            conn = JDBCUtils.getConn();
            statement = conn.createStatement();
            String sql = "SELECT*FROM login WHERE username='" + name + "'andpassword='" + password + "';";
            System.out.println(sql);
            resultSet = statement.executeQuery(sql);
            return resultSet.next();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            JDBCUtils.close(conn, statement, resultSet);
        }
        return false;
    }
    //使用PreparedStatement传参
    public boolean login2(String name, String password) {
        //账号密码正确性校验
        if (name == null || password == null) {
            return false;
        }
        Connection conn = null;
        PreparedStatement statement = null;
        ResultSet resultSet = null;
        try {
            conn = JDBCUtils.getConn();
            String sql = "SELECT*FROM login WHERE username=? and password=?;";
            //预编译SQL
            statement = conn.prepareStatement(sql);
            System.out.println(sql);
            //给参数赋值
            statement.setString(1, name);
            statement.setString(2, password);
            //执行查询
            resultSet = statement.executeQuery();
            return resultSet.next();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            JDBCUtils.close(conn, statement, resultSet);
        }
        return false;
    }
}