Clear User Session

[Shyama Gavulla <sh...@coe.neu.edu>]

-- 
Hi All,

I just moved my webapp from jrun to tomcat. I have a method which clears the
user session. The code snippet is

 Enumeration session_var = session.getAttributeNames();

     while(session_var.hasMoreElements())
     {
         String key=(String)session_var.nextElement();

I am getting an error here and the exception is

java.util.ConcurrentModificationException at
java.util.HashMap$HashIterator.nextEntry

How can I resolve this error.

Thanks a lot in advance
shyam






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Re: Clear User Session

[Tim Funk <fu...@joedog.org>]

Depending on who you talk to its a bug or not a bug in tomcat.

session.getAttributeNames() returns an Enumeration. Under the covers, the 
Enumeration is actually a facade around an Iterator. Iterators are fail-fast 
so if you are enumerating through session attributes and make changes, you 
get the error as you have described.

The arguement is: is  Enumeration allowed to be fail-fast?

In the meantime, 4.1 and 5 were patched to not make the Enumerator 
originating from session.getAttributeNames be fail-fast.


As an aside - if you need to clear out a session: session.invalidate() is 
much easier.

-Tim

Shyama Gavulla wrote:
 > Hi All,
 >
 > I just moved my webapp from jrun to tomcat. I have a method which clears the
 > user session. The code snippet is
 >
 >  Enumeration session_var = session.getAttributeNames();
 >
 >      while(session_var.hasMoreElements())
 >      {
 >          String key=(String)session_var.nextElement();
 >
 > I am getting an error here and the exception is
 >
 > java.util.ConcurrentModificationException at
 > java.util.HashMap$HashIterator.nextEntry
 >
 > How can I resolve this error.
 >
 > Thanks a lot in advance
 > shyam


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