Connection hangs after time of inactivity

Question

In my application, Spring manages connection pool for database access. Hibernate uses these connections for its queries. At first glance, I have no problems with the pool: i

Answer 1

I've had problems like this before when the database is on a seperate box and there's a firewall in between which is set to timeout idle connections.

In some circumstances the firewall cuts off the connection in such a way that the JDBC end doesn't detect, and attempting to use it results in an indefinite block.

In my case it was a custom connection pool which sent a test query down the connection before returning it from the pool. I configured this test query to have a timeout (using Statement.setQueryTimeout) so that it didn't block indefinitely.