This bug is very similar to the
JBSEAM-3295 bug, but for "Page Scope" components this time
Under stress, we have random NPE, "conversation expired" and other strange eroors from time to time in production
This is due to a flaw in the "BijectionInterceptor" class and it is quite easy to reproduce
On a facelets page, we have a datatable with a list of h:commadLink, teh first page of a classic "list entities/showDetail" scheme. The controleur that manages the list is in "Page Scope"
When the user clics on one of the link, then quickly clic on another link, another one etc... without waiting for the detail view to show up, we have two concurrent request addressed to the same Page Scope component (Verified by putting traces in the BijectionInterceptor class)
In BijectionInterceptor, in that case, counter == 2 after line 77 meaning there is two concurrent thread running: the current thread + another one currently "using" the component
The counter will be decrease for the first time on line 82, then a second time on line 129 and so, disinjection will occur on line 134. This occurs while there is another thread "using" the component, causing random NPE and other errors!!!!
In fact this will happen each time counter >1, ie there is more than one "concurrent" request on the same component
This alleviate some questions:-
- is this normal that 2 (or more) concurrent request from the same user/conversation/page acces the same page scope component concurrently (I thought seam was taking care of this and was serializing such requests...
- is this normal that on line 88, components are outjected, only when the last concurrent "user" of the component exits the interceptor and not when each request "eixts" the interceptor?