[LANG-762] Handle or document ReflectionToStringBuilder and ToStringBuilder for collections that are not thread safe

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Fix Version/s: 3.2
• Component/s: lang.builder.*

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"

• Assignee: Unassigned
• Reporter: Gary D. Gregory
• Created: 17/Oct/11 18:20
• Updated: 21/Oct/13 19:51
• Resolved: 21/Oct/13 19:51

Description

Moving discussion here from https://issues.apache.org/jira/browse/POOL-191 ConcurrentModificationException in GenericObjectPool LinkedList.

It is possible to get a ConcurrentModificationException in a LinkedList from a Commons Pool 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.

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)

We should either:

• Document ReflectionToStringBuilder and ToStringBuilder such that call sites use synchronized if the object passed in contains collections that are not thread-safe. F

or example:

    @Override
    public synchronized String toString() {
        return ReflectionToStringBuilder.toString(this);
    }

• Or have our code in ReflectionToStringBuilder and ToStringBuilder lock collections while they are being toString'd.