I think this is missing the key insight that CDI extensions are portable
and that it's "just" providing a 1 class extension that adds 3 orso
build-in beans.
Stuart has a good point about backward compatibility. Servlet impl would have to detect CDI version and skip registration if not 2.0+. I think SERVLET_SPEC-116 should be reopened and the discussion restarted.
Kind regards,
Arjan Tijms
But it's more complicated then it sounds. For example,
HttpServletRequest attibutes might be used as backing storage of the
request context. So that it cannot simply change...
Anyway, I think this problem deserves some attention from both the
CDI and the Servlet EG.
Martin
Dne 8.9.2016 v 13:31 arjan tijms napsal(a):
Hi,
On Thu, Sep 8, 2016 at 1:09 PM, Romain Manni-Bucau
<rmannibucau@gmail.com <mailto:rmannibucau@gmail.com>
<mailto:rmannibucau@gmail.com <mailto:rmannibucau@gmail.com>>> <mailto:arjan.tijms@gmail.com <mailto:arjan.tijms@gmail.com>
wrote:
Hit that issue as well several times.
It is more vicious than it looks like IMO cause CDI will
*never* get
*the* right request for everybody, it is as simple as that.
Any part
of the app can rely on the wrapper level N (of course N being
different for each mentionned parts of the app).
What I was thinking, but maybe I'm wrong, is that the
application never
"just" wraps the request and uses it for itself. It always
passes it to
the container, which then passes it on to the next Filter,
Servlet, or
whatever. So at that point the container code has the opportunity to
store the request as being the "current" one.
E.g. if you do:
RequestDispatcher dispatcher =
servletContext().getRequestDispatcher(...);
dispatcher.forward(wrap(request), response);
Then the RequestDispatcher, which is a container class, receives the
wrapped request and can make it available.
The other way around, eventually every AuthModule, Filter or
Servlet has
to be called by the container at some point. E.g. the "protected
void
service(HttpServletRequest req, HttpServletResponse resp)" is
called by
the container.
So just before the container invokes the HttpServlet#service
method, the
container can store the request, and CDI (via an SPI) can pick it up
from there.
That way in every context you can always have the *current*
request (the
request that's passed in to the last Servlet or Filter call on
the stack).
Kind regards,
Arjan Tijms
Best CDI can do is to provide the request it has (already
the case
and cost pretty much nothing) and enable the user to
produces very
easily its own request from its filter (or equivalent) for
its usage
IMO - which is IMO already doable but maybe there is another
shortcut we can introduce I didnt think about. If you look
one step
further any web framework built on top of CDI does it and
therefore
runs in a well known context.
Romain Manni-Bucau
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2016-09-08 13:03 GMT+02:00 arjan tijms
<arjan.tijms@gmail.com <mailto:arjan.tijms@gmail.com>>>:
Hi,
On Thu, Sep 8, 2016 at 12:40 PM, Martin Kouba
<mkouba@redhat.com <mailto:mkouba@redhat.com>
<mailto:mkouba@redhat.com <mailto:mkouba@redhat.com>>><mailto:cdi-dev@lists.jboss.or
wrote:
that's a good question. In Weld, the request object is
captured during request context activation, i.e. during
ServletRequestListener.requestInitialized()
notification and
before any filter or servlet is invoked. So wrappers are
ignored and the original/first request is used.
Indeed, although do note that some servers (Liberty and
WebLogic
I think) send the
ServletRequestListener.requestInitialized()
notification rather late, and do that after the application
already has seen the request and has had a chance to
wrap it.
This by itself is a separate problem. So on these
servers, Weld
would receive an early request but not necessarily the
earliest.
But TBH I don't think we can fix this easily as I'm not
aware of any portable way to listen for "wrapping
actions".
This would have to happen with Server specific code I guess,
just as Weld now requires an SPI to obtain the current
principal
for injection.
You could say that the Servlet container could store the
request
"somewhere" on a stack structure, just before it invokes the
ServerAuthModule, Filter, Servlet and anything else I
may have
forgotten, and then when control flows back to each Servlet,
Filter, etc unwind that stack.
At the very least the spec for now should perhaps
clarify this?
Kind regards,
Arjan Tijms
Martin
Dne 8.9.2016 v 11:02 arjan tijms napsal(a):
Hi,
The CDI spec defines a built-in bean for the type
HttpServletRequest. In
3.8 it says:
"A servlet container must provide the following
built-in
beans, all of
which have qualifier @Default:
a bean with bean type
javax.servlet.http.HttpServletRequest, allowing
injection of a reference to the HttpServletRequest"
An HttpServletRequest however can be wrapped
multiple
times and by
multiple artefacts. I.e. by a ServerAuthModule,
Filter and a
RequestDispatcher.
The question now is; which version of the
HttpServletRequest is supposed
to be injected?
* The first one in the chain?
* The last one in the chain?
* The current one at a given point in the chain?
A little bit of experimenting seems to indicate
it's now
often "one of
the first ones", e.g. the one that happened to be
current when e.g. a
ServletRequestListener that initialises a
specific CDI
implementation is
called.
I think this is a little confusing, as working
with an
injected request
can now totally ignore the request wrapping that has
been done and break
an application badly.
Thoughts?
Kind regards,
Arjan Tijms
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