[seam-dev] What's the purpose of the method context?

[Dan Allen]

Ah! Now things make sense. In the thread discussing how interceptors
are not applied on self methods, I didn't understand why they weren't
being applied even when I called getInstance() before calling the
method (or as Norman points out, raising a synchronous event). Now I
understand. If I specify the scope explicitly, then it gets the
proxied instance and the interceptors are applied:

// interceptors not applied (MethodContextInterceptor in the way)
((MyComponent) Component.getInstance("myComponent")).callMe()

// interceptors applied
((MyComponent) Component.getInstance("myComponent", ScopeType.EVENT)).callMe();

For a while, I thought I was going insane. In reality, I was being
bitten by the MethodContextInterceptor.

I don't think there is no reason to put the unproxied instead in the
method context. The Seam interceptors, the BijectionInterceptor in
particular, already deal with reentrant calls. So its not like this is
preventing things from breaking. If anything, it is just screwing with
the minds of poor developers wondering why interceptors are not
applied.

-Dan

On Mon, Jun 9, 2008 at 4:55 PM, Norman Richards <orb at nostacktrace.com> wrote:
> I'm looking at a support issue, and I've found a problem with
> MethodContextInterceptor.  The interceptor puts the calling component, by
> name, in the method context so that future calls to getInstance() will find
> that version of the component.  However, it sets the raw, unproxied object
> so that calls to that object will not go through the interceptor chain.
>  (so, an annotation like @CreateProcess won't be triggered).  This seems
> wrong to me, but since I don't understand the purpose of
> MethodContextInterceptor, I can't say for sure.
>
> In case the description above isn't clear, consider a simple component like
> this:
>
> ...
> @Name("foo")
> public class Foo {
>   @RaiseEvent("myEvent")
>   public void actionOne() { }
>
>   @CreateProcess(...)
>   @Observe("myEvent")
>   public void actionTwo() { }
> }
>
>
> When #{foo.one} is invoked, the unproxied Foo instance is put in the method
> context under "foo".  When the event is raised, Events tries to lookup "foo"
> but instead of finding the correct instance in it's normal context, it finds
> the raw instance in the method context.  actionTwo() is called, but there
> are no proxies involved and thus @CreateProcess isn't triggered.
>
> So, what in the world is the MethodContextInterceptor doing there?  Should
> it really be storing the unproxied instance there?
>
>
>
>
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>



-- 
Dan Allen
Software consultant | Author of Seam in Action

http://mojavelinux.com
http://mojavelinux.com/seaminaction

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