DBUtil工具

DBUtil:
DBUtils 是一个jdbc的工具，使用的范围内非常广，主要是为了简化jdbc的代码
核心类：QueryRunner; ResultSetHandler
核心方法：

• update();用来执行DDL（DDL：create alert,drop;）;
• query();用来执行DML（DML:insert update delete;）；
• batch(); 用来执行批处理；
• 调用本方法之前，需要先创建对象，代码如下：

QueryRunner qr = new QueryRunner(JDBCUtils.getDataSource());

DBUtil工具类的创建:

//创建一个接口以实现查询功能
interface IRowMapper{
	void rowMapper(ResultSet res);
}

public class DBUtil {
	//因为加载驱动的代码只需要执行一次即可，没必要重复执行，所以封装到静态代码块中
	static {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	//将建立连接的代码抽取出来，提高代码的复用性
	private static Connection getConnection() {
		try {
			return DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "0314");
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return null;
	}
	//实现查询功能
	public static void select(String sql, IRowMapper rowMapper) {
		Connection connection = null;
		Statement statement = null;
		ResultSet result = null;
		try {
			connection = getConnection();
			statement = connection.createStatement();
			result = statement.executeQuery(sql);
			rowMapper.rowMapper(result);
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			close(result, statement, connection);
		}
	}
	//实现增删改功能
	public static boolean update(String sql) {
		
		Connection connection = null;
		Statement statement = null;
		try {
			connection = getConnection();
			statement = connection.createStatement();
			return statement.executeUpdate(sql) > 0;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			close(statement, connection);
		}
		return false;
	}
	//将关闭资源代码抽取出来，提高代码的复用性
	private static void close(Statement statement, Connection connection) {
		try {
			if (statement != null) {
				statement.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		try {
			if (connection != null) {
				connection.close();
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	//close方法的重载
	private static void close(ResultSet result, Statement statement, Connection connection) {
		try {
			if (result != null) {
				result.close();
			}
			result = null;
		} catch (SQLException e) {
			e.printStackTrace();
		}
		close(statement, connection);
	}
}

DBUtil工具类的使用:

public class Select {
	
	public static void main(String[] args){
		String sql = "select * from user_info";
		class RowMapper implements IRowMapper{
			@Override
			public void rowMapper(ResultSet res) {
				try {
					while (res.next()) {
						String student_id = res.getString("id");
						String userName = res.getString("user_name");
						String password = res.getString("password");
						System.out.println(student_id+" ,"+userName+" ,"+password);
					}
				} catch (SQLException e) {
					e.printStackTrace();
				}
			}		
		}
		IRowMapper rowMapper = new RowMapper();
		DBUtil.select(sql, rowMapper);
	}
}

使用DBUtil工具类实现删除功能:

public class Update {

	public static void main(String[] args) {

			String sql = "delete from user_info";
			if (DBUtil.update(sql)) {
				System.out.println("YSE");
			}else {
				System.out.println("NO");
			}
		}
}