Improve OMEXMLMetadata

[ctrueden]

This branch moves the OMEXMLMetadataImpl#resolveReferences method into the OMEXMLMetadata interface proper. Once the interface itself declares the method, the various explicit casts to OMEXMLMetadataImpl are no longer needed, and interface-driven design works to keep the codebase extensible.

[jburel]

@rleigh-dundee: any comment after Today's review of the PR?

[ghost]

Hmm, I commented on this already. Must have gone onto a different PR or maybe didn't press the comment button.

I'm not an expert with this part of the code. But the patch looks fine, builds fine, and showinf produces valid OMEXML, so I can't see anything which precludes merging.

Couldn't run "ant test" because it was broken on develop today.

[ctrueden]

This is a very straightforward change. When you use an interface-driven design, all public methods should be declared in the interface, not the implementing class. Otherwise, to use the method, you are forced into dangerous casts which prevent third-party extensibility.

The only possible danger I see is if there is some other implementation of OMEXMLMetadata in our codebase (perhaps in OMERO?) which would stop compiling with this change in force. To fix that easily, simply have the alternative implementation implement the new iface method but throw UnsupportedOperationException (or actually implement the method, if it's easy).

[melissalinkert]

There are no other implementations of OMEXMLMetadata, so that's all fine.