[cosmos-dev] Binding service

[Hubert H Leung <hkyleung@xxxxxxxxxx>]

In the design meeting yesterday, we
didn't come to a conclusion on the binding service discussion.  My
view is that the code in the binding service class belong to the framework
code and not extension code.  But Joel likes to give users the flexibility
to control how the component objects get instantiated.  

I have a proposal here for discussion
that can address both of our concerns.  We can provide an API for
the component implementation to control how the class is instantiated through
a factory class.  In fact, the assembly XML is already set up to do
this.  For example: 

<sink cosmos:factory="org.eclipse.cosmos.dc.sample.components.sink.StatisticalPersistor">

The cosmos:factory attribute
defines the factory class that returns an instance of the component implementation.
 We need to require all factory classes to implement a "getInstance"
method that returns a reference to the component object.  The getInstance
method will be invoked by the framework and not extension code.  The
factory can return a singleton class or a new instance of the component
and it allows the use of custom classloaders.  With this approach,
you can replace the object instantiation code in the binding service with
a call to this factory class, and push the rest of the code to the framework
layer (i.e. InboundContext and OutboundContext).  

Joel and Don, what are your comments
on this approach?  


Thanks,
_________________________
Hubert Leung
IBM Toronto Lab
hkyleung@xxxxxxxxxx
905-413-3382