You can find the clue on your own by carefull reading of the provided error message:
"No managed connection available within configured blocking timeout"
This simply means that your connection pool for your mySQL DB ran out of connections. You can monitor the connection pool state (e.g. number of available connections) with the jmx-console.
For a determination of the underlying problem cause you have to provide more detailed information. Which JBoss version ? How many concurrent clients and things like that.
Thank you for your help
My JBoss is 3.2.5 verson. I only try in my computer (one client) and mySQL is 4.0. I really do not know that is Jboss problem or my beans's problems. I also tried install Jboss, mySQL and my application in another computer, there is also the same error. Is there any testing method???
Your JBoss version might be the problem as there is a connection leak bug in JBoss < 3.2.6 (I encountered the same problem as you (at least under heavy load) and after days of JBoss hardcore debugging finally found the causing synchronization bug and fixed it in CVS :-)
-> Check your application behavior with JBosss 3.2.7