snaker-core/src/main/java/org/snaker/engine/access/jdbc/JdbcHelper.java
public static Connection getConnection(DataSource ds) throws SQLException {
    	//通过ThreadLocale中获取Connection，如果为空，则通过dataSource返回新的连接对象
    	Connection conn = (Connection)TransactionObjectHolder.get();
    	if(conn != null) return conn;
		if(ds != null) return ds.getConnection();
		return getDataSource().getConnection();
    }
public static Connection getConnection(DataSource ds) throws SQLException {
    	//通过ThreadLocale中获取Connection，如果为空，则通过dataSource返回新的连接对象
    	Connection conn = (Connection)TransactionObjectHolder.get();
    	if(conn != null) return conn;
		if(ds != null) return ds.getConnection();
		return getDataSource().getConnection();
    }
返回数据库连接对象
@return
@throws SQLException