The most likely cause is that you've got an application-scoped collection (or
perhaps session-scoped) that has been modified in one thread while the iterate
tag is looping in another thread. Nothing really to do with the tag itself.
Quoting [EMAIL PROTECTED]:
> Hi,
> I did some loadtesting on a webapplication where i have several
> jsp-documents, each of them containing iterate-tags.
> When just one user is testing the application everything works fine, but
> during the loadtest i got an exception every now and then.
> The Exception looks like this:
>
> java.util.ConcurrentModificationException
> at java.util.AbstractList$Itr.checkForComodification(Unknown
> Source)
> at java.util.AbstractList$Itr.next(Unknown Source)
> at
> de.intersoft.web.taglib.logik.IterateTag.doAfterBody(IterateTag.java:523)
> at jsp_servlet._bestand.__VertragsdatenDetails._jspService
> (__VertragsdatenDetails.java:3298)
> at weblogic.servlet.jsp.JspBase.service(JspBase.java:27)
> at
> weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
> at
> weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
> at
>
weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:241)
> at
>
de.intersoft.lifestream.wizard.WiControlServlet.leiteRequestWeiter(WiControlServlet.java:621)
> at
> de.intersoft.lifestream.wizard.WiControlServlet.service(WiControlServlet.java:311)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
> at
> weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
> at
> weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
> at
>
weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:2495)
> at
> weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2204)
> at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
> at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
>
> We modified the IterateTag-class slightly, but we didn't write any new
> code, but instead only deleted unneccessary methods in order to have less
> dependencies to other classes.
>
> The doAfterBody Method, where the exception is throws looks like this:
>
> public int doAfterBody() throws JspException
> {
>
> // Render the output from this iteration to the output stream
> if(bodyContent != null)
> {
> TagUtil.writePrevious(pageContext, bodyContent.getString
> ());
> bodyContent.clearBody();
> }
>
> // Decide whether to iterate or quit
> if((lengthValue > 0) && (lengthCount >= lengthValue))
> return (SKIP_BODY);
>
> if(iterator.hasNext())
> {
> // THE EXCEPTION IS THROWN IN THE NEXT ROW !!!!
> Object element = iterator.next();
>
> if(element == null)
> pageContext.removeAttribute(id);
> else
> pageContext.setAttribute(id, element);
> lengthCount++;
> if(indexId != null)
> pageContext.setAttribute(indexId, new
> Integer(getIndex()));
> return (EVAL_BODY_TAG);
> }
> else
> return (SKIP_BODY);
>
> }
>
> I know, that a ConcurrentModificationException occurs if for example the
> underlying collection of the Iterator is changed or the Iterator itself is
> changed while
> you use it in a while(...)-block or for(...)-block or something else, but
> as I said, we didn't write any new code, so I wonder if anyone else
> experienced these ConcurrentModificationExceptions in the Iterate-class yet
> ???
>
> Thanks in advance,
> Dirk Bade
--
Kris Schneider <mailto:[EMAIL PROTECTED]>
D.O.Tech <http://www.dotech.com/>
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