Using xmlunit library in OSGI bundle

To whom it may concern,

We are attempting to use the xmlunit-core library methods in an OSGi application. At runtime, we ran into a situation where the TransformerFactory class was not being resolved. I have included below an explaination of a modification to the xml unit code that we used to address this issue. We are wondering if there is an existing mechanim to address OSGI loading? If not, is there any interest in developing a feature so that we do not have to maintain a separate library with the changes we needed?

Thanks
Jim

After googling the error we found the folowing link https://stackoverflow.com/questions/51687871/unable-to-force-eclipse-to-use-saxon-xslt-processor that suggests we use replace:
TransformerFactory fact = TransformerFactory.newInstance()
with
TransformerFactory fact = new net.sf.saxon.TransformerFactoryImpl();"

We successfully tested that this was our issue by making the following changes to the xmlunit-2.5.1 library code:

**xmlunit-core/src/main/java/org/xmlunit/diff/DefaultComparisonFormatter.java diffs: ***
30,31d29
< import net.sf.saxon.TransformerFactoryImpl;
<
457c455
< final TransformerFactory factory = new TransformerFactoryImpl();

    final TransformerFactory factory = TransformerFactory.newInstance();

** END xmlunit-core/src/main/java/org/xmlunit/diff/DefaultComparisonFormatter.java diffs ***

** xmlunit-core/src/main/java/org/xmlunit/transform/Transformation.java diffs: ***
168c168
< fac = new net.sf.saxon.TransformerFactoryImp();

            fac = TransformerFactory.newInstance();

** END xmlunit-core/src/main/java/org/xmlunit/transform/Transformation.java diffs ***

** xmlunit-core/src/main/java/org/xmlunit/util/Convert.java diffs: ***
34d33
< import net.sf.saxon.TransformerFactoryImpl;
76c75
< fac = new TransformerFactoryImpl();

                fac = TransformerFactory.newInstance();

** END xmlunit-core/src/main/java/org/xmlunit/util/Convert.java ***

Hi Jim

I don't use OSGi myself and am not intimately familiar with it. I've tried to setup things in a way, that should allow all modules to be used as OSGi bundles, so supporting the environment is a goal.
OTOH we do want to support people switching the TransformerFactory using JAXP mechanisms. It is unfortunate this seems to be incompatible with OSGi. Your patch as you describe it, would hard-code Saxon for everybody, which cannot be a goal at all.
I think it is possible to pass a TransformerFactory into XMLUnit's execution contexts explicitly. At least for Convert and Transformation do allow you to specify a factory yourself, DefaultComparisonFormatter doesn't allow this right now, but you could override createXmlTransformer which looks totally inconvenient.
So I feel we need to change DefaultComparisonFormatter but for your other use cases you should be able to provide a TransformerFactory you've created yourself before invoking XMLUnit.
How do you use XMLUnit from your code? I'm not sure the API allows to specify a consistent factory from everywhere.

Stefan

I've opened https://github.com/xmlunit/xmlunit/issues/195 and will get to it sometime in the coming weeks. If there is anything else you'd need please open new issues.

Thanks

Stefan

XMLUnit 2.8.0 has just been released and allows the TransformerFactory to be set explicitly in DefaultComparisonFormatter.