On Wed, Apr 21, 2010 at 9:37 AM, Laurent PETIT <[email protected]>wrote:
> Hi,
>
> Something I don't understand: if the call to (API/getConnection ...)
> fails, there is nothing to close, right ?
>
> So for the problem of ensuring that any open connection is always
> closed, the following pattern seems enough:
>
> (try
> (let [conn (API/getConnection ..)]
> XXX)
> (finally (API/closeConnection conn)))
>
That would be great, but it doesn't work, because "conn" doesn't exist any
more by the time you get to the finally block. That's the problem being
addressed in this thread.
So you can do this:
(let [conn (API/getConnection ...)]
(try
XXX
(finally (API/closeConnection conn))))
But then any exception thrown by API/getConnection is not caught.
So you have to do this:
(try
(let [conn (API/getConnection ...)]
(try
XXX
(finally (API/closeConnection conn))))
(catch ...))
But that still won't work if the catch block also needs access to "conn".
So you wind up with something like this:
(try
(let [conn (API/getConnection ...)]
(try
XXX
(catch ExceptionAfterConnect x (do-something-with conn))
(finally (API/closeConnection conn))))
(catch .ExceptionDuringConnect x (do-something-without-conn))))
--
Mark J. Reed <[email protected]>
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