Java Connection Pooling

Question

I searched for connection pooling and read about it. If I understand it correctly, a connection pool is like a collection of open connections. If a connection is established or created it should be added to the connection pool, and if that connection is closed it should be removed in connection pool; while it is open I can use it again and again.

While reading these tutorials and explanations about connection pooling I have some questions:

1. Can a pool of connections only be used on a certain computer? Like ComputerA cannot share its connection pool with ComputerB?

2. Where should connection.close() be placed?

Is it correct to use a connection ONLY when selecting/loading record? After I got the returned records/data I close the connection at finally statement. Same as adding, editing and deleting records. And while it is processing I place a progress bar so the user will have to wait for it to be completed and to do some process again, which means I will only open connection one at a time.

Thanks for the explanation. :)

Answer 1

Note: I assume we're talking about the java.sql.Connection interface.

Can a pool of connections only be used on a certain computer? Like ComputerA cannot share its connection pool with ComputerB?

A connection exists between a running application and a database. Naturally, two different machines can't share the same running application, so they can't share connections with a database.

Where should connection.close() be placed?

You should always make sure to call close() on a Connection instance after using it (typically in a finally block). If pooling is being used, this will actually return the connection to the pool behind the scenes. Reference: Closing JDBC Connections in Pool

Is it correct to use a connection ONLY when selecting/loading record? After I got the returned records/data I close the connection at finally statement.

Yes, that's correct. You don't want to manually hang on to a Connection reference - use it to execute SQL/DML and then check it back into the pool by calling close() in the finally block, just like you're doing.