jboss + Mysql Connection pool issue

All,
We have issue with connection pool in jboss. We are facing "No Managed Connections" issue. I can see some other also facing the same.
I guess, Connection pool workings well for normal cases.
But I have few queries,
1. Will connection return to pool if there connection got SQLException(Ex: be lock timeout)? We are closing resultset, statement & connection.

2. Do we need to take any extra pre-cautions when reading a "blob"(In Mysql "text) columns?

3. Is there any issue with jboss at destroying a connection and re-creating it? Like, when there are on-demand created connections, pool will destroy those and will create again when needed. I heard, Once a connection destroyed, jboss will hangup if attempt to create new connection. Is it right?

It's been a while since I debugged connection issues but here are some things that always helped me:

Have you looked in MySQL to see what connections are open and what those connections were doing? That might give you some clue.

Also, a thread dump might let you know if some requests are still actively holding connections.

I vaguely recall an issue with exceptions and connections not being released, but cannot seem to find the discussion.

Thanks Peter,

We are trying to see which connection executed for a long time from MySQL end. Because this is happening in production and we are not able to predict when it will be.

And we deployed a small war to take the threaddump, but not able to analyse it. can you please advise how to analyse threads holding the connection.