JDBC的一些API

文章目录

JDBCUtils
数据库连接池
Apache—DBUtils
BasicDAO

JDBC就是Java做了一套关于数据库操作的接口，交给由不同的数据库产商去具体实现。这样，无论是那种类型的数据库，我们导入相应的 jar包，只操作这一套接口就可以实现功能。
下面我做了一张JDBC常用API的思维导图：

------- 2023.1.15加更

JDBCUtils

以上是JDBC的一些常用API，但是连接数据库依然很繁琐。连接数据库和关闭资源是必须的操作，我们可以写一个JDBCUtils，封装连接资源和关闭资源。

public class JDBCutils {public static String user;public static String password;public static String url;public static String driver;static {try {Properties properties = new Properties();properties.load(new FileInputStream("D:\\code\\JDBC\\src\\mysql.properties"));user = properties.getProperty("user");password = properties.getProperty("password");url = properties.getProperty("url");driver = properties.getProperty("driver");} catch (IOException e) {throw new RuntimeException(e);}}public static Connection getConnection(){try {return DriverManager.getConnection(url,user,password);} catch (SQLException e) {throw new RuntimeException(e);}}public static void close(ResultSet set, Statement statement,Connection connection){try {if (set != null){set.close();}if (statement != null){statement.close();}if (connection != null){connection.close();}} catch (SQLException e) {throw new RuntimeException(e);}}
}

这样获取连接和关闭资源我们就不用每次都写一大推重复的代码了，调用这个工具类传参数就可以了。
批处理
需要处理大量的sql语句时，我们可以采取批处理的方式，即，把sql语句打个包，发到数据库执行时让其一次性执行多条。而不是收一条处理一条，再收一条再处理一条。这样提高了效率：

 public void tran() throws SQLException {Connection connection = JDBCutils.getConnection();String sql = "insert into account01 values (null,?,?)";PreparedStatement preparedStatement = connection.prepareStatement(sql);try {System.out.println("开始执行");long start = System.currentTimeMillis();for (int i = 0; i < 5000; i++) {preparedStatement.setString(1,"jack" + i);preparedStatement.setString(2,"666");preparedStatement.addBatch();if ((i + 1) % 1000 == 0){preparedStatement.executeBatch();preparedStatement.clearBatch();}}long end = System.currentTimeMillis();System.out.println("批处理耗时：" + (end - start));} catch (SQLException e) {throw new RuntimeException(e);}finally {JDBCutils.close(null, preparedStatement,connection );}}

数据库连接池

频繁连接、断开数据库性能较低，而且访问量突增的情况下会使得数据库瘫痪，因此引入了数据库连接池技术。连接池作为一个缓冲，既提高了效率，又保护了数据库安全。德鲁伊连接池目前性能最好，应用广泛。

public class JDBCUtilsByDruid {private static DataSource ds;static {Properties properties = new Properties();try {properties.load(new FileInputStream("D:\\code\\JDBC\\src\\druid.properties"));ds = DruidDataSourceFactory.createDataSource(properties);} catch (Exception e) {throw new RuntimeException(e);}}public static Connection getConnection() throws SQLException {return ds.getConnection();}public static void close(ResultSet resultSet, Statement statement, Connection connection) {try {if (resultSet !=null){resultSet.close();}if (statement != null){statement.close();}if (connection != null){connection.close();}} catch (SQLException e) {throw new RuntimeException(e);}}
}

Apache—DBUtils

关闭connection连接后，结果集resultSet也不能再使用了。但是，一直不关连接会浪费资源，因此需要把结果集封装到集合中去。

 public ArrayList<Actor> testArraylist(){Connection connection = null;String aql = "select * from actor where id >= ?";
//        String aql = "select  *from actor";PreparedStatement preparedStatement = null;ResultSet resultSet = null;ArrayList<Actor> list = new ArrayList<>();try {connection = JDBCUtilsByDruid.getConnection();preparedStatement = connection.prepareStatement(aql);preparedStatement.setInt(1,1);resultSet = preparedStatement.executeQuery();while (resultSet.next()) {int id =resultSet.getInt("id");String name = resultSet.getString("name");String sex = resultSet.getString("sex");String brithday = resultSet.getString("brithday");String phone = resultSet.getString("phone");list.add(new Actor(id,name,sex,brithday,phone));}System.out.println("list = " + list);} catch (SQLException e) {throw new RuntimeException(e);} finally {JDBCUtilsByDruid.close(resultSet,preparedStatement,connection);}return list;}

以上是韩老师教我们自己动手封装的办法，相当于是说一下原理和思路。而Apache—DBUtils则提供了一系列办法，我们导入jar包直接调用即可。简化了JDBC开发。开发中我们使用druid和commons.dbutils进行JDBC开发。

BasicDAO

在进一步的使用中，我们封装了BasicDAO类，引入泛型和可变参数进一步提高了通用性和效率。实例见在下的另外一篇文章，满汉楼项目。

public class BasicDAO<T> {private QueryRunner qr = new QueryRunner();public int update(String sql, Object... parameters) {Connection connection = null;try {connection = JDBCUtilsByDruid.getConnection();int update = qr.update(connection, sql, parameters);return update;} catch (SQLException e) {throw new RuntimeException(e);} finally {JDBCUtilsByDruid.close(null,null,connection);}}public List<T> quertMutli(String sql,Class<T> clazz,Object... parameters){return null;}public T quertSingle(String sql,Class<T> clazz,Object... parameters){Connection connection = null;try {connection = JDBCUtilsByDruid.getConnection();return qr.query(connection,sql,new BeanHandler<T>(clazz),parameters);} catch (SQLException e) {throw new RuntimeException(e);} finally {JDBCUtilsByDruid.close(null,null,connection);}}
}