OncePerRequestFilter does not work properly on Error Dispatch on Jetty

[rwinch]

Instances of OncePerRequestFilter do not get invoked for error dispatch types on Jetty (works on Tomcat) even when the following conditions are true:

• The Filter is configured to dispatch on error dispatch types
• The Filter returns false for shouldNotFilterErrorDispatch

Sample

https://github.com/rwinch/onceperrequest-error-dispatch

[rstoyanchev]

The specific scenario is a call to response.sendError(HttpServletResponse.SC_NOT_FOUND) from ResourceHttpRequestHandler. Jetty does the ERROR dispatch within sendError, and that's why the request attribute from OncePerRequestFilter is still set. Tomcat however sets the response, allows the REQUEST dispatch to exit, and then performs the ERROR dispatch.

@rwinch I presume you need this in 5.1.x?