On 7/20/2012 8:53 AM, Jacopo Cappellato wrote:
Thank you Adrian, please see inline:
On Jul 20, 2012, at 9:33 AM, Adrian Crum wrote:
This will be very helpful - thanks for starting it Jacopo!
I will start off with the obvious answers...
LocalDispatcher: The service dispatcher interface.
GenericAbstractDispatcher/GenericDispatcher: LocalDispatcher implementations.
ServiceDispatcher: A service dispatcher "engine". Basically, the
LocalDispatcher implementations delegate to it.
I guess that with "engine" you mean an "helper" class (or similar) and not a
service engine (i.e. implementation of GenericEngine).
Correct.
Apart from this, I see that the ServiceDispatcher is used in a lot of code
directly... shouldn't we use instead the LocalDispatcher? According to your
notes, if I understand them, the only class that should reference the
ServiceDispatcher should be GenericDispatcher that is the only class that
implement LocalDispatcher; but GenericDispatcher doesn't use at all the
ServiceDispatcher.
Correct. Ideally, client code should look something like this:
LocalDispatcher dispatcher = DispatcherFactory.getInstance(...);
GenericDispatcher uses ServiceDispatcher:
GenericAbstractDispatcher.java, line 45.
My next doubt/question is about the GenericEngine interface: how it relates
with LocalDispatcher and ServiceDispatcher?
GenericEngine is the abstraction that allows us to write services in
Java, scripts, etc... So, a service dispatcher uses the GenericEngine to
invoke the service in a language-independent way.
DispatchContext: A bag of objects needed for service execution, plus some
utility methods.
So, is the DispatchContext associated to the LocalDispatcher or instead it is
an implementation detail that makes sense only for the ServiceDispatcher?
It is associated with LocalDispatcher. If you have a LocalDispatcher in
your hand, then you can use it to get a DispatchContext. If you have a
DispatchContext in your hand, you can use it to get a LocalDispatcher.
Keep in mind the DispatchContext contains the objects related to a
service invocation: The service dispatcher, delegator, and security. You
need all three to write a service.
Thanks,
Jacopo
I agree there is a lot of feature envy between classes. The API could be
cleaned up a lot.
From my perspective, the GenericDispatcher.getLocalDispatcher method should
not exist - since it forces you to reference an implementation. Instead, there
should be a separate service dispatcher factory.
-Adrian
On 7/20/2012 7:33 AM, Jacopo Cappellato wrote:
Hi all,
I am a bit confused about the meaning/purpose/responsibilities of the following
classes:
ServiceDispatcher/GenericDispatcher/LocalDispatcher/DispatchContext
Would any of you help me understand the role of each of these classes? They all
see rather intermingled in terms of responsibilities.
For example, what is the purpose of creating two instances with different names
of a dispatcher associated to the same delegator:
LocalDispatcher dispatcher = GenericDispatcher.getLocalDispatcher("entity-" +
delegator.getDelegatorName(), delegator);
and
LocalDispatcher thisDispatcher =
GenericDispatcher.getLocalDispatcher(delegator.getDelegatorName(), delegator);
?
Thanks,
Jacopo
