DO NOT REPLY [Bug 4672] New: - HttpSession attributes get lost or are temporarily unavailable

[bu...@apache.org]

DO NOT REPLY TO THIS EMAIL, BUT PLEASE POST YOUR BUG 
RELATED COMMENTS THROUGH THE WEB INTERFACE AVAILABLE AT
<http://nagoya.apache.org/bugzilla/show_bug.cgi?id=4672>.
ANY REPLY MADE TO THIS MESSAGE WILL NOT BE COLLECTED AND 
INSERTED IN THE BUG DATABASE.

http://nagoya.apache.org/bugzilla/show_bug.cgi?id=4672

HttpSession attributes get lost or are temporarily unavailable

           Summary: HttpSession attributes get lost or are temporarily
                    unavailable
           Product: Tomcat 4
           Version: 4.0.1 Final
          Platform: PC
        OS/Version: Windows NT/2K
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: Unknown
        AssignedTo: tomcat-dev@jakarta.apache.org
        ReportedBy: markus.naeher@web.de


Problem:
Running my servlets, I sometimes get NullPointerExceptions when working with 
objects I have just read from the HttpSession.
In at least one case, I am 100% sure that I did not remove the attribute:
This attribute is set after a successful login and afterwords it is only read. 
There's only one place in my whole code that sets that attribute and many 
places where it is read. The Exception occurs occasionally, unforseeable and at 
any of the places where I read it.
But like usual, there are many other attributes that are set, removed, and read.
I guess it is a timing problem, because I have multiple threads working with 
one session and maybe some attributes are temporarily unavailable while the 
session reorganizes its internal storage (I guess it is a Hashtable or so) 
after numerous add operations.

Workaround:
I am currently testing a modified version of my servlets with synchronized 
access to the session attributes.
So far, the problem has not occured any more.

Proposed fix:
Synchronize access to the session attributes internally.

--
To unsubscribe, e-mail:   <ma...@jakarta.apache.org>
For additional commands, e-mail: <ma...@jakarta.apache.org>