Bug: commit tests require online XML validation

[rleigh]

testValidXML (omexmlService.validateOMEXML) requires network connectivity in order to download the schema for validation. However, we already have a local copy of the schema--can't we just use it directly? This will be both faster and more reliable--no transient test failures. And it will also make it possible to run the tests offline.

[mlinkert]

I don't think we're going to get away from requiring network connectivity, as we'll minimally need to retrieve ​http://www.w3.org/2001/XMLSchema. Using the local schemas may still be possible by using a CatalogReader? (​http://xerces.apache.org/xml-commons/) to do entity resolution (​http://java.dzone.com/articles/use-local-resources-when).

Pushing to 5.1.1, since this needs a day or two of dedicated time and transient validation errors are not a common problem.

[rleigh]

We don't need any network connectivity--it's all done using XML Catalog for the C++ implementation where I implemented a caching catalogue resolver for Xerces-C. There are catalogue files for all schema versions plus ancillary schemas, so it works 100% offline today. It's likely even easier for Java since the built-in Xerces implementation already has a resolver (XMLCatalogResolver). Or it's fairly simple to implement our own if the existing one won't work with the embedded files from the jar. I think the jar already embeds all the catalogues along with the schemas, including the 2001 XMLSchema, so the only missing piece is plugging the catalogue resolver into the parser. There's a top-level catalogue in the released-schema directory which sources all the other catalogues, so the resolver only needs pointing to that one and it will find every schema file.

[jburel]

Moving to 5.1.2 when reviewing model example.
The Downgrade Java integration tests do not use schema resolver. Discussed with Roger yesterday

[mlinkert]

Pushing after discussion with Jean-Marie.

[sbesson]

Should have been addressed by ​https://github.com/openmicroscopy/bioformats/pull/1999/. DEV schemas tests are running without the schema being published.