hi,
first of all the good news. I got rid of the reference warning by
implementing a correct resolving of the component type. I had the
componentType file but the resolving was incorrect. I still have some
issues and comments inline.
Jean-Sebastien Delfino <[EMAIL PROTECTED]> wrote on 09/11/2007 11:17:52
PM:
> Florian Rosenberg wrote:
> > hi,
> >
> > we have created a component implementation for a small RESTful
composition
> > language which does not support references to other components, now we
want
> > to add support for that. The component implementation is similar to
BPEL,
> > but without all the WSDL and partnerlink stuff. Just support for REST
and
> > custom activities to extend the language.
> >
> > An example of using it in the composite file is:
> > <component name="FeedsAggregatorComponent">
> > <implementation.splice
> > baseDir="src/main/resources/flowdir/"
> > path="feeds" url="getFeeds"
> > contentType="text/xml" />
> > <reference name="aggregate"
target="AggregateServiceComponent" />
> >
> > </component>
> > <!-- other stuff goes here -->
> >
> >
> > I need to tell our Splice engine where the references are and how it
can
> > resolve it. The problem is that from the Reference instance, I cannot
> > retrieve an invoker instance to invoke my target as specified in the
> > <reference /> tag. AFAIK, i need a binding and an operation instance to
get
> > an Invoker instance. The binidng is not a problem is can be retrieved
from
> > the reference instance. Furthermore, I need an operation instance; the
name
> > of the operation corresponds to some value in the process definition
that I
> > know.
> >
> > To get the operations i need the interface and thus its interface
contract
> > first. When I do a
> > InterfaceContract contract = _reference.getTargets().get
> > (0).getInterfaceContract();
> >
> >
>
> getTargets().get(0).getInterfaceContract() returns the interface on the
> service that the reference is wired to.
>
> From the component you pasted above I'm guessing that it must be a
> service on the AggregateServiceComponent, and I'm also guessing that
> it's the only service on that component since you didn't specify a
> service name in the reference target attribute.
>
> Can you post the XML describing AggregateServiceComponent?
yes, there is a component called AggregateServiceComponent. I paste the
whole composite file for clarity:
<component name="FeedAggregatorComponent">
<tuscany:implementation.splice name="feedaggregator"
baseDir="src/main/resources/flowdir/"
path="feeds" url="getFeeds"
contentType="text/xml" />
<reference name="aggregateSca" target="AggregateComponent" />
</component>
<component name="AggregateComponent">
<implementation.java class="feedaggregator.FeedAggregateActivity"/>
</component>
> Another comment is that you shouldn't rely on the interface of the
> target service (as there may be no target service if your reference is
> configured to talk to an external endpoint with a binding instead of
> being wired with a target attribute) to determine the interface that
> should be used on the reference.
I understand that I should not rely on the interface contract, but I'm not
sure how to invoke an operation on my reference in a common way without
retrieving the InterfaceContract first. To get an invoker I need to
retrieve a instance of a Binding and an instance of Operation (which I can
get only through the interface, right?
The way I do it now is the following (_reference denote my reference from
the Splice component impl):
List<Binding> bindings = _reference.getBindings();
if (bindings != null && bindings.size() == 0) {
throw new ServiceRuntimeException(String.format("At least one binding is
needed " +
" for the referenced component '%s'.", getName()));
}
Binding b = bindings.get(0);
Interface iface = _reference.getInterfaceContract().getInterface();
List<Operation> operations = iface.getOperations();
Operation targetOp = null;
for (Operation op : operations) { // i require references to implement a
special interface to be called from Splice
if ("invoke".equals(op.getName())) {
targetOp = op;
break;
}
}
Invoker invoker = null;
if (_reference instanceof RuntimeComponentReference && targetOp != null) {
ReferenceBindingProvider provider = ((RuntimeComponentReference)
_reference).getBindingProvider(b);
invoker = provider.createInvoker(targetOp);
}
The above code works fine for references from a Splice workflow. A
reference in the sense of Splice is mainly an extension activity to the
Splice language, such as aggregating RSS feeds in this case. Of course the
component reference are very limited for Splice, by requiring the
implementation of a certain interface (with an invoke method) but that is
fine for this case. We try to leverage as much features as SCA provides ;).
I have tested the above code only with referenced Java components. When
there is no target component, rather an external service - as you said
above - how can I do that or will it work with the above piece of code? I
check some of the existing component implementations but it couldn't found
anything which would make my "invocation of references more clear" to me.
Thanks,
-Florian
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