Top level groups

[adrian.brock]

I've reworked the XsdBinder to add support for top level or global groups.
This lets you look at and change the model of the group.

The main change is to reuse the top level groups
where they are referenced rather than unwrapping them into
their particles and then trying to spot shared elements/types.

Besides being able to modify the binding after the fact
(previously you had to use annotations to do anything with groups)
I think it will also speed up parsing (especially annotation processing)
since each group is only processed once.

See GlobalGroupUnitTestCase
I also created a SharedElementUnitTestCase to make sure I
didn't break this with the change.

[aloubyansky]

This was missing. Thanks, Adrian.

[aloubyansky]

BTW, this introduced dependency on the Java 5 with Collections.emptySet(). Why not Collections.EMPTY_SET instead?

[adrian.brock]

Sorry, yes, it should EMPTY_SET unless you are going to use
jboss retro and convert JBossXB to use java 5.

[adrian.brock]

I also broke the particles for top level groups where it was processing them
multiple times. Once at the top level then again when the group
got referenced.

I've fixed it by only processing group particles when the group
doesn't have any, but there is probably a better way to do this?

e.g.

 +if (groupBinding.getParticles().isEmpty())
 +{
 ctx.pushModelGroup(groupBinding);
 bindModelGroupParticles(ctx, group);
 ctx.popModelGroup();
 +}