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https://issues.apache.org/struts/browse/WW-2167?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=43170#action_43170
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Sean Kleinjung commented on WW-2167:
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It was certainly no problem to look into this... I was experiencing the same
problem with our in-house integration server. Besides, a lot of the process
involved had already been explored in resources linked to in this thread and
elsewhere. In the end, I ended up fixing our application without having to
patch the Struts jar itself. We are using a custom sub-class of
FilterDispatcher that adds the necessary ActionContext cleanup call, which I am
attaching to this issue. Simply add the ActionContextReleasingFilterDispatcher
to your project, and use it in the "filter-class" element in your web.xml
instead of org.apache.struts2.dispatcher.FilterDispatcher. Unfortunately, I
found no work-around for the xwork ContainerImpl leaking a reference to
InternalContext, and so you will still need to manually patch your xwork jar.
Keep in mind, also, that having ANY single leak of this type will prevent the
entire classloader (and all of its classes) from being unloaded. So if you want
an app to unload cleanly, you must fix all the issues discussed here, and be
prepared to research/resolve problems in other libraries. See the link I posted
earlier for some starting points to look at.
> 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
>
> Attachments: FilterDispatcher_leak-fix.java, log_leak.png
>
>
> 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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