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From Chad Schoettger <chad.schoett...@gmail.com>
Subject Removal of the servlet bean context from the httpsession for the ControlFilter
Date Tue, 10 Jan 2006 16:21:32 GMT
Due to some of the issues brought to light by BEEHIVE-1028, I would like to
propose that we remove the ability to store a session bean context in the
HttpSession when using the ControlFilter.

Here's a summary of the issue:

When multiple threads within the same session hit a ControlFilter (with the
ControlFilter's 'useSession' init param set to true).  The same
ServletBeanContext may be used for both threads:

ThreadId   Info
------------- ------------------------------------------
    34       onAcquire
    34       begin dummyControlMethod
    34       end dummyControlMethod
    35       begin dummyControlMethod
    34       onRelease
    35       end dummyControlMethod

Here is what happens in the ServletBeanContext:
- A new ServletBeanContext is created and stored in the session for thread
#34
- The ServletBeanContext's beginContext() method is invoked and passed the
current request and response for thread #34
- Thread #35 sees that there is already a context in the session, grabs it
and calls begin context with its request and response.
- The ServletBeanContext's beginContext() method stores requests and
responses on a Stack.
- Now thread #34 calls ServletBeanContext().endContext() which pops the
Stack (pops thread #35's request and response from the stack
- Now we are at a point in which things are pretty messed up.

I believe that the core issue here is that it is improper to store a bean
context in a session, since the servlet bean context works on a per-request
scope, but at any given time there may be multiple requests made on a single
session.

My recommendation would be to remove the ability to store the bean context
in the session, and just create a new bean context for each request
received. This is a fairly straightforward modification to the ControlFilter
and will resolve this issue.

Questions/Comments?

 - Thanks,
     Chad

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