JAVA-1: Moving the Domain URI from getService() to newInstance()

[Simon Nash <oasis@cjnash.com>]

Mike suggested on today's TC call that the domain URI could be
moved from the SCAClient.getService() method to the
SCAClientFactory.newInstance() method.

To make this work in the VendorA/VendorB situation that we have
been discussing, it would be necessary to also do one of the
following:
  a) add additional methods setDomainURI() and getDomainURI() to
     the SCAClientFactory abstract class
  b) require every factory to have a one-argument constructor that
     takes the domain URI as an argument.  This could be enforced by
     putting a private no-argument constructor and a protected
     one-argument contructor on the SCAClientFactory abstract class,
     together with a protected concrete getDomainURI() method that
     returns the domain URI.
Of these two options, my preference is for b).

To see why this in needed, consider the case of client code running
within a VendorB runtime that has injected a VendorB factory finder.
If the client code wants to access a domain DomainA that uses a
VendorA implementation of the factory, the sequence of events is
as follows:

1. Client calls SCAClientFactory.newInstance(properties, classLoader,
                                              "DomainA")

2. The VendorB factory finder looks up the VendorA factory class using
    the supplied properties and classLoader.

3. The VendorB factory finder does one of the following:
     a) calls a no-argument constructor on the VendorA factory class,
        then calls setDomainURI("DomainA") on the returned factory
     b) calls a one-argument constructor on the VendorA factory class,
        passing "DomainA" as the constructor argument
    In either case the result is an instance of Vendor A's factory
    implementation class that is bound to DomainA.  If the domain URI
    were not passed in this step, the VendorA factory object would not
    know which domain URI to use for getService() calls.

4. Client calls the getService(interfaze, serviceURI) method on the
    VendorA/DomainA factory object returned by step 3.  The VendorA
    concrete factory implementation class calls this.getDomainURI()
    to find the correct domain URI to use.

The above scheme is slightly more complex than the current proposal,
but the "future-proofing" benefit may justify this.

   Simon