Jersey creates multiple provider instances if a class implements more than one provider interface

[mkarg]

JAX-RS Specification 2.1 Chapter 4.1 Line 1: "By default a single instance of each provider class is instantiated for each JAX-RS application."

Jersey clearly violates this rule as it creates one instance of such a class per provider interface this class implements. For example, in case a class is annotated with @Provider and implements both ContainerRequestFilter and ContainerResponseFilter then Jersey creates two instances, instead one instance. In case this class additionally implements Feature then Jersey even creates a third instance.

Can be reproduce using the following code:

@Provider
public class MyProvider implements Feature, ContainerRequestFilter, ContainerResponseFilter {
	@Override
	public boolean configure(FeatureContext context) {
		System.out.println("Feature.this = " + this);
		return true;
	}
	@Override
	public void filter(ContainerRequestContext requestContext) {
		System.out.println("ContainerRequestFilter.this = " + this);
	}
	@Override
	public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) {
		System.out.println("ContainerResponseFilter.this = " + this);
	}

}

Here is the result it prints after the first invocation finished:

Feature.this = eu.headcrashing.bugs.MyProvider@6cee903a
...
ContainerRequestFilter.this = eu.headcrashing.bugs.MyProvider@575a86ae
ContainerResponseFilter.this = eu.headcrashing.bugs.MyProvider@69767b65

To be compliant to the mentioned chapter of the spec, the result MUST be this instead:

Feature.this = eu.headcrashing.bugs.MyProvider@6cee903a
...
ContainerRequestFilter.this = eu.headcrashing.bugs.MyProvider@6cee903a
ContainerResponseFilter.this = eu.headcrashing.bugs.MyProvider@6cee903a

[mkarg]

Please see this JAX-RS API issue for reference: jakartaee/rest#605.

[mkarg]

FYI: Using jVisualVM I noticed that the three mentioned instances actually are kept in memory even after a GC got performed. This looks like a memory leak, as at least the Feature instance is of no use at runtime (the other two instances actually get used by every invocation).