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Posted to users@tomcat.apache.org by Kent Kurima <nw...@hotmail.com> on 2002/02/19 16:51:14 UTC

ConcurrentModificationException error

When I try to remove some information from the session I get a 
ConcurrentModificationException error.

tomcat 3.X did not have this problem, but tomcat 4.X is complaining about 
this.

here is a section of code that is having the problem

java.util.Enumeration sessionNames = session.getAttributeNames();
while(sessionNames.hasMoreElements()){
	String lstrSessionName = (String)sessionNames.nextElement();
	if (!lvecTempVar.contains(lstrSessionName)) {
  		session.removeAttribute(lstrSessionName);
	}
}

anyone have any ideas?

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Re: ConcurrentModificationException error

Posted by Eelco den Heijer <ee...@objectivation.com>.
Kent Kurima wrote:
> 
> When I try to remove some information from the session I get a
> ConcurrentModificationException error.
> 
> tomcat 3.X did not have this problem, but tomcat 4.X is complaining about
> this.
> 
> here is a section of code that is having the problem
> 
> java.util.Enumeration sessionNames = session.getAttributeNames();
> while(sessionNames.hasMoreElements()){
>         String lstrSessionName = (String)sessionNames.nextElement();
>         if (!lvecTempVar.contains(lstrSessionName)) {
>                 session.removeAttribute(lstrSessionName);
>         }

Hi Kent,

Probably, another servlet instance is accessing that attr. of the 
session; you have to synchronize access to it:

while(sessionNames.hasMoreElements()){
        String lstrSessionName = (String)sessionNames.nextElement();
        if (!lvecTempVar.contains(lstrSessionName)) {
		synchronized (session) {
	                session.removeAttribute(lstrSessionName);
		}
        }

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