Hi all, recently I found that "ConcurrentModificationException" happened a few times in the server log. I know that JBoss 4.0.3sp1 has a bug:http://jira.jboss.com/jira/browse/JBAS-3137 on that. It's said that this problem is fixed. But now I met this again. Please see below. Also I found that before and after this exception happened, there were warning message "[org.jboss.resource.connectionmanager.CachedConnectionManager] Closing a connection for you. Please close them yourself:" around it.
My configuration: JBoss 4.2.1GA + JDK 1.5.0_13. Any suggestion is appreciated. Thanks!

2007-11-13 08:22:57,418 ERROR [org.jboss.web.tomcat.service.session.JBossCacheService] externalizeSe
ssion(): exception occurred externalizing session SessionBasedClusteredSession[id: QyohhhjQAARi2HkAr
eBYvg**.server1 lastAccessedTime: 1194942177369 version: 765 lastOutdated: 0]
java.util.ConcurrentModificationException
 at java.util.HashMap$HashIterator.nextEntry(HashMap.java:841)
 at java.util.HashMap$EntryIterator.next(HashMap.java:883)
 at java.util.HashMap$EntryIterator.next(HashMap.java:881)
 at java.util.HashMap.writeObject(HashMap.java:1037)
 at sun.reflect.GeneratedMethodAccessor183.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:917)
 at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1339)
 at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1290)
 at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1079)
 at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1375)
 at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1347)
 at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1290)
 at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1079)
 at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:302)
 at java.util.concurrent.ConcurrentHashMap.writeObject(ConcurrentHashMap.java:1380)
 at sun.reflect.GeneratedMethodAccessor191.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:917)
 at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1339)
 at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1290)
 at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1079)
 at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:302)
 at org.jboss.web.tomcat.service.session.SessionBasedClusteredSession.writeExternal(SessionBasedClus
teredSession.java:175)
 at org.jboss.web.tomcat.service.session.JBossCacheService.externalizeSession(JBossCacheService.java
:1027)
 at org.jboss.web.tomcat.service.session.JBossCacheService.putSession(JBossCacheService.java:316)
 at org.jboss.web.tomcat.service.session.JBossCacheClusteredSession.processSessionRepl(JBossCacheClu
steredSession.java:121)
 at org.jboss.web.tomcat.service.session.JBossCacheManager.processSessionRepl(JBossCacheManager.java
:1097)
 at org.jboss.web.tomcat.service.session.JBossCacheManager.storeSession(JBossCacheManager.java:652)
 at org.jboss.web.tomcat.service.session.InstantSnapshotManager.snapshot(InstantSnapshotManager.java
:49)
 at org.jboss.web.tomcat.service.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:98)

 at org.jboss.web.tomcat.service.session.JvmRouteValve.invoke(JvmRouteValve.java:84)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
 at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
 at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:437)
 at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:381)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:595)
2007-11-13 08:22:57,421 INFO [org.jboss.resource.connectionmanager.CachedConnectionManager] Closing
 a connection for you. Please close them yourself: org.jboss.resource.adapter.jdbc.WrappedConnectio
n@701eae
java.lang.Throwable: STACKTRACE
 at org.jboss.resource.connectionmanager.CachedConnectionManager.registerConnection(CachedConnection
Manager.java:290)
 at org.jboss.resource.connectionmanager.BaseConnectionManager2.allocateConnection(BaseConnectionMan
ager2.java:417)
 at org.jboss.resource.connectionmanager.BaseConnectionManager2$ConnectionManagerProxy.allocateConne
ction(BaseConnectionManager2.java:842)
 at org.jboss.resource.adapter.jdbc.WrapperDataSource.getConnection(WrapperDataSource.java:88)
 at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:112)
 at com.nsite.processserver.ConnectionManager.getConnection(ConnectionManager.java:174)
 at org.apache.jsp.c.rulesdesigner.DecisionTableBuilder_jsp._jspService(DecisionTableBuilder_jsp.jav
a:133)
 at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:387)
 at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
 at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at com.nsite.filter.URLProcessorFilter.doFilter(URLProcessorFilter.java:39)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at com.nsite.filter.GZIPFilter.doFilter(GZIPFilter.java:23)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at com.nsite.config.RequestContextManager.doFilter(RequestContextManager.java:31)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.springframework.orm.hibernate3.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionI
nViewFilter.java:174)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:77)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235
)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:179)

 at org.jboss.web.tomcat.service.session.ClusteredSessionValve.invoke(ClusteredSessionValve.java:87)

 at org.jboss.web.tomcat.service.session.JvmRouteValve.invoke(JvmRouteValve.java:84)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104)
 at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241)
 at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:437)
 at org.apache.coyote.ajp.AjpProtocol$AjpConnectionHandler.process(AjpProtocol.java:381)
 at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
 at java.lang.Thread.run(Thread.java:595)