When running an application in an app server, the advice that comes the most often is to rely on the server db connection pooling system, rather than on a third party like c3p0, proxool or dbcp.

Why ?
Are these 3rd party pools not fully stable - or considered as less than those from app servers vendors - or is it simply to rationalize, not doubling a fonctionnality already present in the server ?

My problem is that the application I am working on is based on XML/RPC for communcation between an java application client, and business classes (not EJB). Hence there is only a frontend servlet needed by XML/RPC, but the business classes aren't strictly dependent on the app server.

Which has a great advantage : unit tests can be done without launching the server, both on mapped objects and on business classes.

How could I preserve this advantage and build a production grade application with app server pooling ?

what about using two different hibernate configuration files. one that uses the connection pool provided by the app server and one that uses dbcp?

in your build script (I just guess you are using ant) you could easily switch between the hibernate config files!

The problem is that what you test isn't striclty what you put in production.

For example, I encounter a strange problem with c3p0 right now, and I'm trying to solve it. But if I don't manage to, I would have to make significant changes in my code, just to have it work correctly. And that would introduce large diff