DbUtil

public class DbUtil {
	private static String url = "jdbc:mariadb://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC";
	private static String username = "test";
	private static String password = "test";

	public static Connection getConnection() {
		Connection conn = null;
		try {
			Class.forName("org.mariadb.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		try {
			conn = DriverManager.getConnection(url, username, password);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}

}

public class UserDao {

	//查询所有
	public List<User> findAll(){
		 //创建连接
        Connection conn = DbUtil.getConnection();
        //创建SQL执行工具
        QueryRunner queryRunner = new QueryRunner();
        List<User> list = null;
        try {
            //执行SQL查询，并获取结果
        	//BeanListHandler 映射多个对象
            list = queryRunner.query(conn, "select * from user", new BeanListHandler<>(User.class));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //关闭数据库连接
        DbUtils.closeQuietly(conn);
        return list;
	}

	//添加
	public void save(User user) {
		Connection conn = DbUtil.getConnection();
        //创建SQL执行工具
        QueryRunner queryRunner = new QueryRunner();
        int rows = 0;
        try {
            //执行SQL插入
        	//返回受影响有多少行
            rows = queryRunner.update(conn, "INSERT INTO user(name, age,imgurl) VALUES(?,?,?)",
            		new Object[] {user.getName(),user.getAge(),user.getImgurl()});
            //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //关闭数据库连接
        DbUtils.closeQuietly(conn);
	}

	//查找单个
	public User findOne(int id) {
		 //创建连接
        Connection conn = DbUtil.getConnection();
        //创建SQL执行工具
        QueryRunner queryRunner = new QueryRunner();
        User user = new User();
        try {
            //执行SQL查询，并获取结果   
        	//BeanHandler 映射成一个对象
        	user = queryRunner.query(conn, "select * from user where id=?", new BeanHandler<>(User.class),
        			new Object[] {id});
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //关闭数据库连接
        DbUtils.closeQuietly(conn);
        return user;
	}

	//修改
	public void update(User user) {
		Connection conn = DbUtil.getConnection();
        //创建SQL执行工具
        QueryRunner queryRunner = new QueryRunner();
        int rows = 0;
        try {
            //执行SQL插入
            rows = queryRunner.update(conn, "update user set name=?,age=?,imgurl=? where id=?",
            		new Object[] {user.getName(),user.getAge(),user.getImgurl(),user.getId()});
            //new Object[] {user.getName(),user.getAge(),user.getImgurl()} 设置参数
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //关闭数据库连接
        DbUtils.closeQuietly(conn);
	}

	//删除
	public void delete(int id) {
		Connection conn = DbUtil.getConnection();
        //创建SQL执行工具
        QueryRunner queryRunner = new QueryRunner();
        int rows = 0;
        try {
            //执行SQL插入
            rows = queryRunner.update(conn,"delete from user where id=?", new Object[] {id});
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //关闭数据库连接
        DbUtils.closeQuietly(conn);
	}
}