Java 中封装JDBC连接到JDBCUtils工具类的详解

//这是一个工具类，完成mysql的连接和关闭资源
public class JDBCUtils {
    //定义相关的属性(4个),因为只需要一份，因此我们做成static
    private static String user;//用户名
    private static String password;//密码
    private static String url; //url
    private static String driver;//驱动名
    //初始化相关属性值，放到静态代码块中完成
    static {
        try {
            Properties properties = new Properties();
            properties.load(new FileInputStream("src\\mysql.properties"));
            //读取相关的属性值
            user = properties.getProperty("user");
            password = properties.getProperty("password");
            url = properties.getProperty("url");
            driver = properties.getProperty("driver");
        } catch (IOException e) {
            //在实际开发中，我们可以这样处理
            //1.将编译异常转成，运行异常
            //2.这时调用者，可以选择捕获该异常，也可以选择默认处理该异常，比较方便
            throw new RuntimeException(e);
        }
    }
    //连接方法，返回Connection
    public static Connection getConnection() {
        try {
            Class.forName(driver);
            return DriverManager.getConnection(url, user, password);
        } catch (Exception e) {
            //1.将编译异常转成，运行异常
            //2.这时调用者，可以选择捕获该异常，也可以选择默认处理该异常，比较方便
            throw new RuntimeException(e);
        }
    }
    //关闭相关资源
    /*
        1.resultSet 结果集
        2.prepareStatement 或者 Statement
        3.connection
        4.如果需要关闭资源，就传入对象，否则传入null
     */
    public static void close(ResultSet set, Statement statement, Connection connection) {
        try {
            //判断是否为null
            if (set != null) {
                set.close();
            }
            if (statement != null) {
                statement.close();
            }
            if (connection != null) {
                connection.close();
            }
        } catch (SQLException e) {
            //将编译异常，转换为运行异常抛出
            throw new RuntimeException(e);
        }
    }
}

public class JDBCUtils_Use {
    //使用JDBCUtils 进行DML操作(insert update delete)
    @Test
    public void testDML() {
        //1.得到连接
        Connection connection = null;
        //2.组织一个sql
        //更新记录
//        String sql = "UPDATE actor SET NAME=? WHERE id=?";
        //删除记录
        String sql = "DELETE FROM actor WHERE id=?";
        //添加记录
//        String sql = "INSERT INTO actor VALUES(?,?,?,?,?)";
        PreparedStatement preparedStatement = null;
        //创建PrepareStatement对象
        try {
            connection = JDBCUtils.getConnection();
            preparedStatement = connection.prepareStatement(sql);
            //添加记录
//            preparedStatement.setInt(1, 3);
//            preparedStatement.setString(2, "周润发");
//            preparedStatement.setString(3, "男");
//            preparedStatement.setString(4, "1999-01-10");
//            preparedStatement.setString(5, "1234567890");
            //修改记录
//            preparedStatement.setString(1, "周星驰");
//            preparedStatement.setInt(2, 1);
            //删除记录
            preparedStatement.setInt(1, 1);
            int rows = preparedStatement.executeUpdate();
            System.out.println(rows > 0 ? "执行成功" : "执行失败");
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //关闭资源
            JDBCUtils.close(null, preparedStatement, connection);
        }
    }
    @Test
    public void testSelect() {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;
        try {
            //1.得到连接
            connection = JDBCUtils.getConnection();
            String sql = "SELECT id,name,borndate FROM ACTOR WHERE id = ?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setInt(1, 2);
            //执行得到结果集
            resultSet = preparedStatement.executeQuery();
            while (resultSet.next()) {
                String name = resultSet.getString("name");
                int id = resultSet.getInt("id");
                Date borndate = resultSet.getDate("borndate");
                System.out.println(id + "\t" + name + "\t" + borndate);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCUtils.close(resultSet, preparedStatement, connection);
        }
    }
}

执行成功
2 王宝强 1980-01-03