2013/4/5 Jean-Claude Haw-King-Chon <jchaw-king-c...@medifirst.fr>:
> Hi,
>
> I use the connection pool of tomcat7 and set a connection in a ThreadLocal.
> The context is a web application : the threadLocal is configured when the
> http request is initialized. The jdbc connection is closed and removed from
> the threadLocal when the resquest is destroyed.
>
1. What exactly do you mean by "initialized" and "destroyed"?
>
> If I'm not mistaken, each http request is treated by one thread by tomcat.
> So, I have one jdbc connection for each request ( = thread).
2. No. It depends on how you use it and at what points in time you look at it.
If you look at it in a call chain, e.g. using try{ } finally block in
a Filter, then yes, all calls inside of "try" belong to the same
thread.
If you return processing to Tomcat and Tomcat makes a different call
into your code (e.g. using Async or Comet APIs), then that call can be
using a different thread from a thread pool.
> (...)
>
> My problem appears when I use Ajax. For 2 successive ajax request, I have
> the error "Connection closed" : it's a random problem (the stacktrace is not
> the same for the 2 attemps and it's not depending of the thread execution
> order).
>
> I know this issue :
> http://tomcat.apache.org/tomcat-7.0-doc/jndi-datasource-examples-howto.html#Random_Connection_Closed_Exceptions
>
> "These can occur when one request gets a db connection from the connection
> pool and closes it twice. When using a connection pool, closing the
> connection just returns it to the pool for reuse by another request, it
> doesn't close the connection. And Tomcat uses multiple threads to handle
> concurrent requests"
>
> But, I'm sure, I always close the connection only once.
> I use too the "validationQuery" and "testOnBorrow" parameters.
>
> Is it possible that the connection pool returns the same connection for 2
> different threads?
>
You can check its hash code.
> So I don't understand why my connection is closed during the treatment.
>
Best regards,
Konstantin Kolinko
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