Fix #411 No Object Wrapper Identity requirement for dispatch

[gregw]

Fix #411 No Object Wrapper Identity requirement for dispatch

[gregw]

@markt-asf @stuartwdouglas what are your thoughts on this one? Any chance of it getting in 6.0? If not, then I'm interested to know if there would ever be a time we could do such changes?

I think it is probably our only opportunity to fix this issue - which makes servlets really bad for async applications at the benefit of vanishingly few applications. Note that I'm proposing keeping object identity in the filter chain, which is probably where most of the downcasting apps do their stuff - it is only when going via a dispatch that changes the paths etc. that I propose allowing identity to be broken in return for immutable references that work with async.

[stuartwdouglas]

I think this looks good.

If this requirement was removed from the filter chain I would be a bit more conservative, but just removing it from RequestDispatcher and async dispatch is fine, and could greatly simplify our implementation.

[markt-asf]

+1

[gregw]

OK then I think this is ready to merge. But I'll leave for a few days just in case others wish to comment.