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https://issues.apache.org/struts/browse/WW-2167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_42505
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Adam Crume commented on WW-2167:
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My understanding is that finalize() will be called eventually (unless the JVM
shuts down), although it is not guaranteed to be called immediately. In either
case, as I said I tried the same experiment with a project containing an action
and a project containing a servlet, and the finalize() method was being called
for the static object in the servlet but not the action. I tried this several
times and the results were quite repeatable.
Class unloading is enabled. Personally, I can't imagine why on earth it would
be disabled for an application server. Every time an app was restarted, memory
would leak.
Besides, if class unloading was disabled in my JVM, the static object in the
servlet would never be garbage collected and the finalize() method would never
be called, but this was clearly not the case.
> Memory leak when app stopped
> ----------------------------
>
> Key: WW-2167
> URL: https://issues.apache.org/struts/browse/WW-2167
> Project: Struts 2
> Issue Type: Bug
> Affects Versions: 2.0.9
> Environment: WebSphere 6.1.0.9 (non-network deploy) on Windows XP
> Professional
> java version "1.5.0"
> Java(TM) 2 Runtime Environment, Standard Edition (build pwi32devifx-20070608
> (SR5+IY99712))
> IBM J9 VM (build 2.3, J2RE 1.5.0 IBM J9 2.3 Windows XP x86-32
> j9vmwi3223-20070426 (JIT enabled)
> J9VM - 20070420_12448_lHdSMR
> JIT - 20070419_1806_r8
> GC - 200704_19)
> JCL - 20070608
> Reporter: Adam Crume
> Fix For: 2.1.2
>
>
> Struts 2 somehow prevents the app's classes from being garbage collected when
> the application is stopped or undeployed.
> I created a barebones Struts 2 app with an action with the following code:
> private static final Object x = new Object() {
> {
> System.out.println("================== Object created:
> " + hashCode() + " ===================");
> }
> protected void finalize() throws Throwable {
> System.out.println("**************** Object finalized:
> " + hashCode() + " *********************");
> };
> };
> Because of this static field, a message should be printed when the class is
> initialized and when it is garbage collected. "Object created" would be
> printed out whenever I went to the action for the first time, but restarting
> the app never printed "Object finalized." This is not an issue with garbage
> collection in my web container because doing the same thing with a servlet
> resulted in both messages being printed.
> One problem is that the FilterDispatcher.init() method sets a ThreadLocal but
> never clears it. I fixed that by adding ActionContext.setContext(null); to
> the end of the init() method, but that didn't solve the larger problem.
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