Jersey: Detect when Controller Class is Created

Question

I've implemented a JAX-RS server application using Jersey 2.24.

I use the Guice-HK2 bridge so that the controller classes (those annotated with @Path) are injected with dependencies from Guice, not Jersey/HK2.

However, HK2 still creates instances of the @Path annotated classes itself.

Is there a way I can plug into Jersey/HK2 so that I'm notified when a @Path annotated class is created? Like some sort of lifecycle listener? Every time a @Path annotated class is created by Jersey/HK2 I want to do some registering/logging of that class.

If Guice were doing the actual creation of the @Path annotated class I think I could do it using a generic Provider but that's not available in this case, since Jersey/HK2 is creating the actual instance.

Thank you!!

Answer 1

I think the least intrusive way would be to just use AOP. HK2 offers AOP. What you can do is create a ConstructorInterceptor. Something like

public class LoggingConstructorInterceptor implements ConstructorInterceptor {

    private static final Logger LOG
            = Logger.getLogger(LoggingConstructorInterceptor.class.getName());

    @Override
    public Object construct(ConstructorInvocation invocation) throws Throwable {
        Constructor ctor = invocation.getConstructor();
        LOG.log(Level.INFO, "Creating: {0}", ctor.getDeclaringClass().getName());

        // returned instance from constructor invocation.
        Object instance = invocation.proceed();
        LOG.log(Level.INFO, "Created Instance: {0}", instance.toString());

        return instance;
    }
}

Then create a InterceptorService to only use the interceptor for classes annotated with @Path

public class PathInterceptionService implements InterceptionService {

    private static final ConstructorInterceptor CTOR_INTERCEPTOR
            = new LoggingConstructorInterceptor();
    private final static List<ConstructorInterceptor> CTOR_LIST
            = Collections.singletonList(CTOR_INTERCEPTOR);

    @Override
    public Filter getDescriptorFilter() {
        return BuilderHelper.allFilter();
    }

    @Override
    public List<MethodInterceptor> getMethodInterceptors(Method method) {
        return null;
    }

    @Override
    public List<ConstructorInterceptor> getConstructorInterceptors(Constructor<?> ctor) {
        if (ctor.getDeclaringClass().isAnnotationPresent(Path.class)) {
            return CTOR_LIST;
        }
        return null;
    }
}

Then just register the InterceptionService and ConstructorInterceptor with the DI system

new ResourceConfig()
        .register(new AbstractBinder(){
            @Override
            public void configure() {
                bind(PathInterceptionService.class)
                        .to(InterceptionService.class)
                        .in(Singleton.class);
                    bind(LoggingConstructorInterceptor.class)
                        .to(ConstructorInterceptor.class)
                        .in(Singleton.class);
            }
        });

See complete example in this Gist

See Also:

• HK2 documentation on AOP