Raymond, thanks for the corrections, I was not using the latest spec and I
made up the nesting. I append my original note with the correct scdl to
restart the thread. As for your questions, (1) yes, the intention is that
InnerComposite be executed in the same address space as OuterComposite, and
(2) for the purposes of this thread, I am focusing on composite references,
but similar issues apply to composite services, so in particular, we can
imagine a third (or zeroth) component in OuterComposite that is wired to
SourceComponent to invoke it locally via its composite service.
-------------------- Original Note ----------------------
One of the composite reference scenarios outlined by Jeremy has a local wire
between the Component and the Reference, and an external wire from the
CompositeComponent to a sibling Component or Reference (aka the "uncle").
For instance:
<composite xmlns="http://www.osoa.org/xmlns/sca/1.0";
name="OuterComposite">
<component name="SourceComponent">
<implementation.composite name="InnerComposite"/>
<reference name="TargetComponentRef">TargetComponent</reference>
</component>
<component name="TargetComponent">
<implementation.java class="TargetImpl"/>
</component>
</composite>
<composite xmlns="http://www.osoa.org/xmlns/sca/1.0";
name="InnerComposite">
<service name="InnerComponentService" target="InnerSourceComponent">
<interface.java interface="..."/>
</service>
<component name="InnerSourceComponent">
<implementation.java class="SourceImpl"/>
<reference name="target">TargetComponentRef</reference>
</component>
<reference name="TargetComponentRef">
<interface.java interface="..."/>
</reference>
</composite>
There are two issues to consider: (1) how the composite reference
"TargetComponentRef" gets modeled, and (2) how is the composite reference
"TargetComponentRef" is wired by the wiring infrastructure.
(1) Model and runtime objects for a targetless composite reference. A
targetless composite reference does not have a binding and it is not
specified by a component and given a target. So, at the model level the
object that represents this kind of composite reference is not a
BoundReferenceDefinition nor a ReferenceTarget, but it can be a plain
ReferenceDefinition instance that is considered separately by
CompositeBuilder to get its runtime representation built. In fact,
ReferenceLoader seems to deal with this case already, returning a
ReferenceDefinition instance when there is no binding, so it's just a matter
of setting up the CompositeBuilder and registering a builder for the
ReferenceDefinition with the builder registry. At the runtime level we seem
to have agreed on the definition of a CompositeReference class that extends
ReferenceExtension. The other piece that is needed is a builder that creates
a CompositeReference, that is registered with the builder registry and that
takes a ReferenceDefinition. This can't be a BindingBuilder, so it seems a
new class is needed, perhaps ReferenceBuilder or CompositeReferenceBuilder.
(2) Wiring a targetless composite reference. In the example above,
TargetComponentRef does not specify an explicit target or a binding, its
target is intended to be resolved by a component that is implemented by the
composite that contains TargetComponentRef, SourceComponent in this case.
When SourceComponent is being built by CompositeBuilder, a runtime
representation is created for it, e.g., a CompositeComponentImpl. When an
outbound wire is being added to the created CompositeComponentImpl by
WireService, via the BuilderRegistry, the CompositeComponentImpl should pass
on this wire to the runtime representation of TargetComponentRef, i.e.,
CompositeReference. This way, a CompositeComponent "shares" the outbound
wire of its target with the corresponding CompositeReference. This way, the
behavior of ConnectorImpl can be to just connect the outbound wire in
SourceComponent's CompositeComponentImpl and not to recurse down into
TargetComponentRef as it is sharing the same wire that was already
connected.
One question that arises is: should passing on wires happen recursively
down? For instance, since the reference in InnerSourceComponent is to a
composite reference, should the outbound wire given to the
CompositeComponent that represents InnerSourceComponent come from the
composite reference, i.e., TargetComponentRef?
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