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Date: Tue, 31 Oct 2017 09:03:01 +0000 (UTC)
From: "Dmitri Blinov (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Created] (JEXL-244) Webapp classloader memory leaks
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archived-at: Tue, 31 Oct 2017 09:03:09 -0000

Dmitri Blinov created JEXL-244:
----------------------------------

             Summary: Webapp classloader memory leaks
                 Key: JEXL-244
                 URL: https://issues.apache.org/jira/browse/JEXL-244
             Project: Commons JEXL
          Issue Type: Bug
    Affects Versions: 3.1
         Environment: Inside J2EE container when Jexl library is included in the deployed .war file
            Reporter: Dmitri Blinov


I have spotted that the following constructions, like for example in JexlEngine.java
{code}
    public static final Object TRY_FAILED = new Object() {
        @Override
        public String toString() {
            return "tryExecute failed";
        }
    };
{code}
are not garbage collected when web-app is reloaded and its classloader is released. This is because circular references are created when static class members are initialized with non-static inner/anonymous classes, which are holding implicit references to its enclosing class and thus to its static class type. There are other such examples in JexlEngine.java like
{code}
    protected static final java.lang.ThreadLocal<JexlContext.ThreadLocal> CONTEXT =             new java.lang.ThreadLocal<JexlContext.ThreadLocal>() {..

    protected static final java.lang.ThreadLocal<JexlEngine> ENGINE =
            new java.lang.ThreadLocal<JexlEngine>() {...

{code}

The issue is easily resolved if for example the following pattern is followed

{code}
    public static class FailObject extends Object {
        @Override
        public String toString() {
            return "tryExecute failed";
        }
    }

    public static final Object TRY_FAILED = new FailObject();
{code}


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