What I ended up doing for this problem, to avoid the exception, was to
make a local modification in ManageableCollectionUtil. It still
throws the exception (if needed) but my specialized list collection
class is now easily coerced to a ManageableCollection with my
replacement code.
This is a hack, but a much smaller hack than trying to specialize either
the objectConverter or the collectionConverter to do the wrapping.
I would like to see the CollectionConverter interface extended with a
method:
private ManageableCollectionFactory getManageableCollectionFactory()
such that the ManageableCollectionFactory class would be used in much
the same way that ManageableCollectionUtil is ued.
The ManageableCollectionFactory would continue to throw the
"unsupported" JcrMapping exception (if needed), but presumably would
wrap all of the application's collection classes correctly.
Dan Connelly wrote:
I want to use a custom collectionConverter, MyCollectionConverterImpl.
That collectionConverter can decide what to do with "unsupported"
collections from my *given* object model. (Object model cannot be
changed.) In particular, MyCollectionConverterImpl will wrap an
unsupported collection as a ManageableCollection and delegate its work
to a standard collection converter.
The collection type is discovered by reflection in the
objectConverter, so it cannot be coerced in the ocm mapping.
Unfortunately, the default objectConverter invokes its own wrapping
tool, ManageableCollectionUtil, just before the call to
insertCollection in the custom collectionConverter.
ManageableCollectionUtil will throw an exception before the custom
collectionConverter gets its chance to wrap the unsupported collection
type. The call to insertCollection in the custom
collectionConverter is never invoked.
A workaround would be to over-ride method insertCollectionFields using
a custom objectConverter. However, this method is private in the
standard objectConverter. Thus the method work cannot be delegated.
Code would need to be copied into the custom objectConverter. Not
good. But even if this method was public and code copying was not
needed, the object converter is not the right place for collection
conversions.
Why not make the collectionConverters responsible for throwing an
exception on (truly) unsupported collection types?
Don't throw this exception from ManageableCollectionUtil. Just leave
an "unsupported" collection type alone there and let the
collectionConverter deal with any unsupported collection type that may
be given to it.
-- Dan
