code: protected void checkTransactionSupported(Connection conn) throws SQLException, DbRuntimeException {
  		if (null == isSupportTransaction) {
  			isSupportTransaction = conn.getMetaData().supportsTransactions();
  		}
  		if (false == isSupportTransaction) {
  			throw new DbRuntimeException("Transaction not supported for current database!");
  		}
  	}
docs: 检查数据库是否支持事务，此项检查同一个数据源只检查一次，如果不支持抛出DbRuntimeException异常
  
  @param conn Connection
  @throws SQLException 获取元数据信息失败
  @throws DbRuntimeException 不支持事务