[Opensource] ConcurrentModificationException

[Mike Traum]

Are you putting anything in the session which isn't synchronized?

I assume you're running this through an IDE? I don't believe
org.netbeans.modules.web.monitor.server.MonitorFilter is normally in the
chain, so I assume you're using JBuilder or NetBeans. If so, I'd check
their resources for a description. If you find a description which
points back to Expresso, please let us know.

thanks,
mike

On Mon, 2004-01-19 at 10:17, S. W. wrote:
> Hi All,
> 
> I am new to Expresso. I have used Expresso to build a
> small applications. When I run my codes which I used a
> vector to store the data retrieved from MySQL and
> iterated through this vector to get the data and
> display the data in front-end, I got the following
> error:
> 
> Apache Tomcat/4.0.6 - HTTP Status 500 - Internal
> Server Error
> 
> --------------------------------------------------------------------------------
> 
> type Exception report
> 
> message Internal Server Error
> 
> description The server encountered an internal error
> (Internal Server Error) that prevented it from
> fulfilling this request.
> 
> exception 
> 
> java.util.ConcurrentModificationException
> 	at
> java.util.HashMap$HashIterator.nextEntry(HashMap.java:762)
> 	at
> java.util.HashMap$KeyIterator.next(HashMap.java:798)
> 	at
> org.apache.catalina.util.Enumerator.nextElement(Enumerator.java:166)
> 	at
> org.netbeans.modules.web.monitor.server.MonitorFilter.getSessionAttributes(MonitorFilter.java:809)
> 	at
> org.netbeans.modules.web.monitor.server.MonitorFilter.getSessionIn(MonitorFilter.java:746)
> 	at
> org.netbeans.modules.web.monitor.server.MonitorFilter.getDataBefore(MonitorFilter.java:488)
> 	at
> org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:182)
> 	at
> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
> 	at
> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
> 	at
> org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
> 	at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
> 	at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
> 	at
> org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
> 	at
> org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
> 	at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
> 	at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
> 	at
> org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347)
> 	at
> org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
> 	at
> org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
> 	at
> org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
> 	at
> org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
> 	at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
> 	at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
> 	at
> org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
> 	at
> org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
> 	at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
> 	at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
> 	at
> org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027)
> 	at
> org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125)
> 	at java.lang.Thread.run(Thread.java:536)
> 
> What caused the problem? I can't figure out. Anybody
> knows.
> 
> Thanks in advance!
> 
> Regards,
> 
> Sally
> 
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-- 

Mike Traum
--
JGroup Expert 
Expresso Core Developer 
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