HttpSeesion.removeAttribute does not garbage collect object 2005-06-29 - By Frans Verhoef
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Hi,
When calling the System.gc() method, you only suggest to the JVM to do garbage
collecting. Whether the JVM is going to garbage collect is up to the JVM itself
. As such different JVM implementation might have different ways of handling
garbage collecting.
Cheers,
Frans
On Wed, 29 Jun 2005 15:35:40 +0530, Partha Ranjan Das wrote:
>?Hi J2EE Gurus,
>
>?We are having a seemingly peculiar problem.
>
>?In this case an activeX client makes multiple HTTP calls to a
>?servelt in a web server serially. The servlet has a single method
>?to handle all these HTTP calls (called "FP calls") . This method
>?has many switch-case statements for these FP calls. In the first
>?"case" statement, it calls the EJB tier and gets a collection of
>?serializeable Value Object (Or Data Transfer Objects) and this
>?collection is maintained in the HttpSession by using
>?HttpSession.setAttribute("XYZ",object). Now, when the following
>?call, made by the same ActiveX client, (in this FP series of calls)
>?comes for the next FP call, it uses the collection stored in
>?session. The last FP call, after doing business operations, does
>?HttpSession.removeAttribute("XYZ"). So at this point, we assume
>?that this collection, which was so far bound to key "XYZ", should
>?be ?ready for garbage collection....right?
>?Wrong. When we ran JProfiler to find what all objects are there in
>?the memory at this point (after calling GC manually using the
>?profiler),--- we find that those objects, constituting that
>?collection, which is supposed to be garbage collected, are not at
>?all garbage collected. What is more ashtonishing is that we find
>?half of these objects are lying in the EJB tier and half in the web
>?tier. But the servlet responds to all the FP calls and the ActiveX
>?displays all the information required. This means that the HTTP
>?responses for all the HTTP "FP call" requests have been duely and
>?fully made.
>?Does anybody have any idea why, after calling
>?session.removeAttribute also, these objects are not garbage
>?collected and also why half of these objects are still lying in the
>?EJB tier, even after EJB method has ended and GC is called using
>?the profiler? We are not maintaining this collection as a static
>?propoerty of any of the classes, either in web or EJB tier. We are
>?using WSAD 5.1.
>?Thanks in advance,
>
>?Regards,
>?Partha
>
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