Listener refused the connection with the following error:

Exception in thread "main" java.sql.SQLException: Listener refused the connection with the following error:
ORA-12519, TNS:no appropriate service handler found
The Connection descriptor used by the client was:
username:1521:sid

以上错误的原因是：没有正常关闭Statement, ResultSet, Connection

添加关闭语句，则可