Delegate the Java 18 XPathFactory property methods

[ppkarwasz]

Java 18 added setProperty(String, String) and getProperty(String) to javax.xml.xpath.XPathFactory. Their default implementations throw UnsupportedOperationException, and the JDK's XPathFactoryImpl overrides both to accept its jdk.xml.xpath* processing limits.

This library compiles against the Java 8 API, so the wrapper overrode only the methods that existed there and inherited those defaults. On Java 18 or later that meant a secured factory answered UnsupportedOperationException for a property the delegate would have accepted: an operator could neither tighten jdk.xml.xpathExprGrpLimit and friends per factory, nor read back the effective value to audit it. It contradicts the package Javadoc's promise that "features, properties, and attributes delegate to" the implementation.

Nothing could be loosened this way either — the failure is loud and in the safe direction — so this is a limitation of the wrapper rather than a weakening of the securing.

Both methods are now delegated through method handles, the way newDefaultInstance already reaches a static method added in a later release. MethodHandleFactory gains a general findVirtual companion to its existing findStatic.

Two things a reviewer will want to know:

• Neither method carries @Override, and neither can. At release 8 the supertype declares no such method, so the annotation would not compile. They override at run time on Java 18 or later, which is the point; both carry a Javadoc note saying so, since the natural instinct is to add the annotation.
• Where the handle is absent (Java 8 through 17) they throw UnsupportedOperationException, matching the behaviour that release inherits — though the path is unreachable through an XPathFactory reference there, since the method does not exist to be called.

The delegate's own exceptions pass through unwrapped, so an unrecognised property still surfaces its IllegalArgumentException.

Tests

Gated on the presence of the method rather than on a version string:

	JDK 17	JDK 25	without the delegation (JDK 25)
delegatesTheJava18PropertyApi	skip	pass	fail
reportsAnUnknownPropertyLikeTheDelegate	skip	pass	fail

They reach the pair reflectively — the suite compiles at release 8 too — which also means they exercise exactly the runtime dispatch a Java 18 caller gets. Both were verified to fail with the delegation removed, so they discriminate rather than passing vacuously.

Full surefire matrix green on JDK 17 and on JDK 25.

🤖 Generated with Claude Code