Java中JDBC的使用教程详解

<!--Mysql数据库驱动-->
<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.27</version>
</dependency>

//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 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "root");
//4.定义sql语句
String sql = "update account set balance = 500 where id = 1";
//5.获取执行sql的对象 Statement
Statement stmt = conn.createStatement();
//6.执行sql
int count = stmt.executeUpdate(sql);
//7.处理结果
System.out.println(count);
//8.释放资源
stmt.close();
conn.close();

static {
    try {
        java.sql.DriverManager.registerDriver(new Driver());
    } catch (SQLException E) {
        throw new RuntimeException("Can't register driver!");
    }
}

Statement stmt = null;
Connection conn = null;
try {
    //1. 注册驱动
    Class.forName("com.mysql.jdbc.Driver");
    //2. 定义sql
    String sql = "insert into account values(null,'王五',3000)";
    //3.获取Connection对象conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
    //4.获取执行sql的对象 Statement
    stmt = conn.createStatement();
    //5.执行sql
    int count = stmt.executeUpdate(sql);//影响的行数
    //6.处理结果
    System.out.println(count);
    if(count > 0){
        System.out.println("添加成功！");
    }else{
        System.out.println("添加失败！");
    } 
} catch (ClassNotFoundException e) {
    e.printStackTrace();
} catch (SQLException e) {
    e.printStackTrace();
}finally {
    //stmt.close();
    //7. 释放资源
    //避免空指针异常
    if(stmt != null){
        try {
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    if(conn != null){
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

//循环判断游标是否是最后一行末尾。
while(rs.next()){
    //获取数据
    //6.2 获取数据
    int id = rs.getInt(1);
    String name = rs.getString("name");
    double balance = rs.getDouble(3);
    
    System.out.println(id + "---" + name + "---" + balance);
}

public class JDBCUtils {
	private static String url;
	private static String user;
	private static String password;
	private static String driver;
	
	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();
			System.out.println(path);///D:/ideaProjects/itcast/out/production/day04_jdbc/jdbc.properties
			//2. 加载文件
		   // pro.load(new FileReader("D:\\IdeaProjects\\itcast\\day04_jdbc\\src\\jdbc.properties"));
			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();
		}
	}


	
	public static Connection getConnection() throws SQLException {

		return DriverManager.getConnection(url, user, password);
	}

	
	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();
			}
		}
	}


	
	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();
			}
		}
	}

}

CREATE TABLE USER(
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(32),
	PASSWORD VARCHAR(32)

);

INSERT INTO USER VALUES(NULL,'zhangsan','123');
INSERT INTO USER VALUES(NULL,'lisi','234');

public class JDBCDemo9 {

	public static void main(String[] args) {
		//1.键盘录入，接受用户名和密码
		Scanner sc = new Scanner(System.in);
		System.out.println("请输入用户名：");
		String username = sc.nextLine();
		System.out.println("请输入密码：");
		String password = sc.nextLine();
		//2.调用方法
		boolean flag = new JDBCDemo9().login(username, password);
		//3.判断结果，输出不同语句
		if(flag){
			//登录成功
			System.out.println("登录成功！");
		}else{
			System.out.println("用户名或密码错误！");
		}


	}



	
	public boolean login(String username ,String password){
		if(username == null || password == null){
			return false;
		}
		//连接数据库判断是否登录成功
		Connection conn = null;
		Statement stmt =  null;
		ResultSet rs = null;
		//1.获取连接
		try {
			conn =  JDBCUtils.getConnection();
			//2.定义sql
			String sql = "select from user where username = '"+username+"' and password = '"+password+"' ";
			//3.获取执行sql的对象
			stmt = conn.createStatement();
			//4.执行查询
			rs = stmt.executeQuery(sql);
			//5.判断
		   /if(rs.next()){//如果有下一行，则返回true
				return true;
			}else{
				return false;
			}*/
		   return rs.next();//如果有下一行，则返回true

		} catch (SQLException e) {
			e.printStackTrace();
		}finally {
			JDBCUtils.close(rs,stmt,conn);
		}


		return false;
	}
}

public class JDBCDemo10 {

	public static void main(String[] args) {
		Connection conn = null;
		PreparedStatement pstmt1 = null;
		PreparedStatement pstmt2 = null;

		try {
			//1.获取连接
			conn = JDBCUtils.getConnection();
			//开启事务
			conn.setAutoCommit(false);

			//2.定义sql
			//2.1 张三 - 500
			String sql1 = "update account set balance = balance - ? where id = ?";
			//2.2 李四 + 500
			String sql2 = "update account set balance = balance + ? where id = ?";
			//3.获取执行sql对象
			pstmt1 = conn.prepareStatement(sql1);
			pstmt2 = conn.prepareStatement(sql2);
			//4. 设置参数
			pstmt1.setDouble(1,500);
			pstmt1.setInt(2,1);

			pstmt2.setDouble(1,500);
			pstmt2.setInt(2,2);
			//5.执行sql
			pstmt1.executeUpdate();
			// 手动制造异常
			int i = 3/0;

			pstmt2.executeUpdate();
			//提交事务
			conn.commit();
		} catch (Exception e) {
			//事务回滚
			try {
				if(conn != null) {
					conn.rollback();
				}
			} catch (SQLException e1) {
				e1.printStackTrace();
			}
			e.printStackTrace();
		}finally {
			JDBCUtils.close(pstmt1,conn);
			JDBCUtils.close(pstmt2,null);
		}


	}

}