This is a pretty general question and I apologize in advance if it's been covered here before. I'm having problems using hibernate and c3p0 wherein my c3p0 connection pool becomes exhausted. I'm trying to debug this problem by putting stacktrace logging calls into the c3p0 source on checkin/checkout of connections. I'm sure there's a better way to do this, can anyone suggest anything?

I've encountered a similar problem using Proxool.

I've also debugged and located the problem:

The connections are exhausted in the following case:

You load entities within a transaction, and commit the transaction. If you try to access a uninitialized association, hibernate initializes lazy associations: a connection is requested and not freed anymore.

Therefore my solution was to free them manually:

in the getter of one-to-one associations put the following:

if (!((HibernateProxy) ref).getHibernateLazyInitializer().getSession()
.getJDBCContext().isTransactionInProgress()) {
((HibernateProxy) ref).getHibernateLazyInitializer().getSession()
.getJDBCContext().afterNontransactionalQuery(true);
}


(while ref is the proxy).

on one-to-many:

if (!persistentSet.getCurrentSession().getJDBCContext().isTransactionInProgress()) {
persistentSet.getCurrentSession().getJDBCContext().afterNontransactionalQuery(true);
}

(while persistenSet is the Hibernate Proxy (PersistentSet)), if you use another collection type, use it instead.


The core is if you are not in a transaction, hibernate forgets to free the connection used for lazy loading, afterNonTransactionalQuery does this.


Hope this helps!