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https://issues.apache.org/jira/browse/POOL-191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13128677#comment-13128677
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Phil Steitz commented on POOL-191:
----------------------------------
Having dug a little bit into the lang code, I am inclined to bounce this back
to [lang]. At the very least, the various private collection traversal
thingies should come with warning labels. They should *not* be used in
concurrent applications and the javadoc should indicate that. There do not
appear to be any guards to prevent exactly this kind of exception, when the
code breaks access protection and then ends up throwing CoMod exceptions
because private collections are being modified while iterated. Other than the
lack of a threadsafe toString, I don't see a [pool] bug here.
> ConcurrentModificationException in GenericObjectPool LinkedList
> ---------------------------------------------------------------
>
> Key: POOL-191
> URL: https://issues.apache.org/jira/browse/POOL-191
> Project: Commons Pool
> Issue Type: Bug
> Affects Versions: 1.5.6
> Environment: Apache Maven 3.0.3 (r1075438; 2011-02-28 12:31:09-0500)
> Maven home: C:\Java\apache-maven-3.0.3\bin\..
> Java version: 1.6.0_24, vendor: Sun Microsystems Inc.
> Java home: C:\Program Files\Java\jdk1.6.0_24\jre
> Default locale: en_US, platform encoding: Cp1252
> OS name: "windows 7", version: "6.1", arch: "amd64", family: "windows"
> Reporter: Gary D. Gregory
>
> It is possible to get a {{ConcurrentModificationException}} in a
> {{LinkedList}} from a {{GenericObjectPool}}.
> This happens when I call {{ReflectionToStringBuilder.toString(this)}} from a
> subclass of {{GenericObjectPool}}. My guess is that it would happen with just
> {{ReflectionToStringBuilder.toString(gop)}}. IOW, subclassing does not have
> anything to do with it I would venture.
> For example, in this stack trace {{JmsSessionPool}} is a subclass of
> {{GenericObjectPool}}.
> {noformat}
> java.util.ConcurrentModificationException
> at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761)
> at java.util.LinkedList$ListItr.next(LinkedList.java:696)
> at java.util.AbstractCollection.toString(AbstractCollection.java:421)
> at java.lang.String.valueOf(String.java:2826)
> at java.lang.StringBuffer.append(StringBuffer.java:219)
> at
> org.apache.commons.lang3.builder.ToStringStyle.appendDetail(ToStringStyle.java:598)
> at
> org.apache.commons.lang3.builder.ToStringStyle.appendInternal(ToStringStyle.java:473)
> at
> org.apache.commons.lang3.builder.ToStringStyle.append(ToStringStyle.java:436)
> at
> org.apache.commons.lang3.builder.ToStringBuilder.append(ToStringBuilder.java:848)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.appendFieldsIn(ReflectionToStringBuilder.java:528)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:692)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:288)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:119)
> at
> com.seagullsw.appinterface.comm.jms.JmsSessionPool.toString(JmsSessionPool.java:120)
> at java.lang.String.valueOf(String.java:2826)
> at java.lang.StringBuffer.append(StringBuffer.java:219)
> at
> org.apache.commons.lang3.builder.ToStringStyle.appendDetail(ToStringStyle.java:586)
> at
> org.apache.commons.lang3.builder.ToStringStyle.appendInternal(ToStringStyle.java:550)
> at
> org.apache.commons.lang3.builder.ToStringStyle.append(ToStringStyle.java:436)
> at
> org.apache.commons.lang3.builder.ToStringBuilder.append(ToStringBuilder.java:848)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.appendFieldsIn(ReflectionToStringBuilder.java:528)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:689)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:288)
> at
> org.apache.commons.lang3.builder.ReflectionToStringBuilder.toString(ReflectionToStringBuilder.java:119)
> at
> com.seagullsw.appinterface.server.comm.BasicCommunicationManager.toString(BasicCommunicationManager.java:828)
> at
> com.seagullsw.appinterface.server.comm.BasicCommunicationManager.toString(BasicCommunicationManager.java:817)
> at java.lang.String.valueOf(String.java:2826)
> at java.lang.StringBuilder.append(StringBuilder.java:115)
> at
> com.seagullsw.appinterface.server.AisHelper.waitForCommuncationManagers(AisHelper.java:217)
> at com.seagullsw.appinterface.server.AisHelper.start(AisHelper.java:136)
> at
> com.seagullsw.appinterface.server.AisHelper.startFromResource(AisHelper.java:161)
> at
> com.seagullsw.appinterface.server.AbstractServerJunit4.startServer(AbstractServerJunit4.java:179)
> at
> com.seagullsw.appinterface.server.comm.jms.AbstractJmsRoundtripMaxConcurrencyTestCase.setUpOnce(AbstractJmsRoundtripMaxConcurrencyTestCase.java:141)
> at
> com.seagullsw.appinterface.server.comm.jms.ibmmq.JmsRoundtripMaxConcurrency032TestCase.setUpOnce(JmsRoundtripMaxConcurrency032TestCase.java:40)
> {noformat}
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