@Priority is not always picked up correctly for JAX-RS providers

[chkal]

There are still some cases where ordering of JAX-RS providers via @Priority doesn't work correctly. In my case there are two ExceptionMapper instances for the same exception type but with different priorities. Jersey fails to pick up the @Priority, which results in a default priority of Priorities.USER for both mappers and therefore in random ordering at runtime.

IMO the problem actually occurs for all JAX-RS provider types. It occurs with Jersey 2.28. See the following analysis for details:

Custom providers are looked up in the Providers class like this:

jersey/core-common/src/main/java/org/glassfish/jersey/internal/inject/Providers.java

Lines 287 to 290 in 895c293

	List<ServiceHolder<T>> providers = getServiceHolders(injectionManager,
	contract,
	Comparator.comparingInt(Providers::getPriority),
	CustomAnnotationLiteral.INSTANCE);

The getServiceHolders method gets a Comparator which uses Providers.getPriority() to order the providers according to the @Priority annotation.

jersey/core-common/src/main/java/org/glassfish/jersey/internal/inject/Providers.java

Lines 363 to 371 in 895c293

	private static int getPriority(Class<?> serviceClass) {
	Priority annotation = serviceClass.getAnnotation(Priority.class);
	if (annotation != null) {
	return annotation.value();
	}
	// default priority
	return Priorities.USER;
	}

Everything is fine so far.

The problem is that Providers.getPriority() isn't always called with the actual provider implementation class but sometimes gets an instance of org.glassfish.jersey.inject.hk2.InstanceSupplierFactoryBridge. This means that Jersey sometimes looks for the @Priority on the wrong class and is ignoring the @Priority on the actual implementation class.

The Providers class seems to use ServiceHolder.getImplementationClass() to get the type of the provider class, which doesn't work correctly in all cases.

jersey/core-common/src/main/java/org/glassfish/jersey/internal/inject/Providers.java

Lines 313 to 315 in 895c293

	List<ServiceHolder<T>> serviceHolders = injectionManager.getAllServiceHolders(contract, qualifiers);
	serviceHolders.sort((o1, o2) -> objectComparator.compare(o1.getImplementationClass(), o2.getImplementationClass()));
	return serviceHolders;

My current guess is that it should use ServiceHolder.getImplementation**Type**() instead. But I'll need to verify that. I'll try to create a failing integration tests for this issue.-

[chkal]

Please see #4100 for a possible fix. Although I'm not completely sure if it is the best place for a fix.

[chkal]

I created #4101 which contains an integration test which reproduces this issue. I hope this helps.

[jansupol]

@chkal #4103 Should fix the issue.