Always use the system default TransformerFactory in FormatXmlHelper

[ianprime0509]

Closes #2911
Closes #2913

The implementation of FormatXmlHelper relies on a non-standard TransformerFactory attribute, indent-number, which is not supported by all implementations. By using TransformerFactory.newDefaultInstance instead of TransformerFactory.newInstance, the system default implementation (com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl on OpenJDK-derived JDKs) will be used regardless of any other implementations which might be present on the classpath.

---

Unfortunately, I don't see any way to add or update any tests for this change without introducing a dependency on another XML library. To ensure this change has the expected behavior, I used the same reproduction steps as in #2911 (include Saxon-HE in a small test project): the exception thrown when invoking the WireMockServer constructor no longer appears when using a version with this change installed to my local Maven repository.

Another possible approach would be to try to unify this logic with

wiremock/src/main/java/com/github/tomakehurst/wiremock/common/xml/XmlNode.java

Lines 44 to 57 in 00d0329

	TransformerFactory transformerFactory;
	try {
	// Optimization to get likely transformerFactory directly, rather than going through
	// FactoryFinder#find
	transformerFactory =
	(TransformerFactory)
	Class.forName(
	"com.sun.org.apache.xalan.internal.xsltc.trax.TransformerFactoryImpl")
	.getDeclaredConstructor()
	.newInstance();
	} catch (Exception e) {
	transformerFactory = TransformerFactory.newInstance();
	}
	transformerFactory.setAttribute("indent-number", 2);

, which appears to serve a similar purpose, but was written before Java 11 was the baseline (TransformerFactory.newDefaultInstance was introduced in Java 9). Let me know if you'd like me to try to consider that in this PR as well.

References

• New JSON and XML handlebars helpers #2904
• FormatXmlHelper constructor may throw IllegalArgumentException depending on the TransformerFactory impl #2911
• FormatXmlHelper constructor throws exception when TransformerFactory does not support attribute #2913

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• The PR request is well described and justified, including the body and the references
• The PR title represents the desired changelog entry
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• Test coverage that demonstrates that the change works as expected
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[welcor]

Looks like the build failed due to a port conflict - it will probably run ok if triggered again.

[tomakehurst]

Ugh, do you mind re-running Spotless and pushing?

The rollover to the new year is causing it to fail now.

[ianprime0509]

Sure, no problem, I just rebased and ran Spotless on top to update the copyright year.

[ianprime0509]

Hmm, it looks like just one of the Spotless jobs in CI is failing for copyright years on files which aren't being changed in this PR. Running Spotless on my end didn't touch these files, but I also use Linux while the failing CI job is using Windows. Should I update those files manually?

[tomakehurst]

We were just discussing this. Look like a bug in the latest Spotless and we were considering disabling it for Windows for now, but if you don't mind making those changes it would definitely help move things forward.

[ianprime0509]

Sounds good, I just added an extra commit on top which should address all the files that were failing in that CI run.

[com2ghz]

With temurin-21 i am facing this exception when I try to upgrade from wiremock-standalone:3.9.1 to 3.10.0 and get this exception. Looks like this issue is describing this problem:

Caused by: java.lang.IllegalArgumentException: Unrecognized configuration feature: indent-number
	at net.sf.saxon.Configuration.setConfigurationProperty(Configuration.java:4373)
	at net.sf.saxon.jaxp.SaxonTransformerFactory.setAttribute(SaxonTransformerFactory.java:340)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.helpers.FormatXmlHelper.<init>(FormatXmlHelper.java:68)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.helpers.WireMockHelpers$30.<init>(WireMockHelpers.java:284)
	at com.github.tomakehurst.wiremock.extension.responsetemplating.helpers.WireMockHelpers.<clinit>(WireMockHelpers.java:283)