SimpleApplicationEventMulticaster does not filter ApplicationEvents correctly [SPR-5974]

[spring-projects-issues]

Oliver Drotbohm opened SPR-5974 and commented

JavaDoc of ApplicationListener says:

"As of Spring 3.0, an ApplicationListener can generically declare the event type that it is interested in. When registered with a Spring ApplicationContext, events will be filtered accordingly, with the listener getting invoked for matching event objects only."

Despite that, SimpleApplicationEventMulticaster notifies all ApplicationListeners regardless of the type you paramterized it with (see multicastEvent(..). This leads to ClasCastExceptions when declaring a subtype of ApplicationEvent as parameter of ApplicationListener.

---

Affects: 3.0 M3

Issue Links:

• GenericTypeResolver returns Object for parameterized parameters [SPR-7389] #12047 GenericTypeResolver returns Object for parameterized parameters

[spring-projects-issues]

Juergen Hoeller commented

What exactly doesn't work there? The code in AbstractApplicationEventMulticaster's getApplicationListeners method should do the filtering there... And our ApplicationContextEventTests do test generically declared event subtypes. Is it something specific that doesn't work for you?

Juergen

[spring-projects-issues]

Oliver Drotbohm commented

Hm... I repeatedly got a ClassCastException and just took a glance a SimpleApplicationEventMulticaster, which looked like it'd retrun the plain list of ApplicationListeners. After trying to rereproduce this, I blatantly failed :). I got it working now. Feel free to mark the ticket as invalid.

Anyway, thanks...

[spring-projects-issues]

Juergen Hoeller commented

Alright - good to hear that it works for you now...

Juergen

[spring-projects-issues]

Marek Romanowski commented

I have similar problem with Spring 3.0.3. With listener like this:

public class OfferUpdatingPolicyCreateEventListenerImpl
implements ApplicationListener<PolicyCreateEvent<AbstractPolicy>> {
@Override
public void onApplicationEvent(final PolicyCreateEvent<AbstractPolicy> event) {
}
}

and

public class OfferUpdatingPolicyCreateEventListenerImpl
implements ApplicationListener<PolicyCreateEvent<? extends AbstractPolicy>> {
@Override
public void onApplicationEvent(final PolicyCreateEvent<? extends AbstractPolicy> event) {
}
}

tests fail because of:
Caused by: java.lang.ClassCastException: org.springframework.context.event.ContextRefreshedEvent cannot be cast to [...].PolicyCreateEvent

So it looks like application contexts sends all events to this listener. But when I change my event listener code to:

public class OfferUpdatingPolicyCreateEventListenerImpl
implements ApplicationListener<PolicyCreateEvent> {
@Override
public void onApplicationEvent(final PolicyCreateEvent event) {
}
}

tests pass. It looks like problem lies in extractClass(Class, Type) method, while checking should listener instance be informed about event. In my case second argument is instance of ParametrizedTypeImpl, while if statement checks only for TypeVariable and GenericArrayType types. Probably same problem will appear when WildcardType will be passed. Here's stacktrace:

GenericTypeResolver.extractClass(Class, Type) line: 171	
GenericTypeResolver.doResolveTypeArguments(Class, Class, Class) line: 150	
GenericTypeResolver.resolveTypeArguments(Class, Class) line: 135	
GenericTypeResolver.resolveTypeArgument(Class, Class) line: 114	
GenericApplicationListenerAdapter.supportsEventType(Class<ApplicationEvent>) line: 55	
SimpleApplicationEventMulticaster(AbstractApplicationEventMulticaster).supportsEvent(ApplicationListener, Class<ApplicationEvent>, Class) line: 179	
SimpleApplicationEventMulticaster(AbstractApplicationEventMulticaster).getApplicationListeners(ApplicationEvent) line: 140	
SimpleApplicationEventMulticaster.multicastEvent(ApplicationEvent) line: 86	
GenericApplicationContext(AbstractApplicationContext).publishEvent(ApplicationEvent) line: 301	
GenericApplicationContext(AbstractApplicationContext).finishRefresh() line: 888	
GenericApplicationContext(AbstractApplicationContext).refresh() line: 426	
GenericXmlContextLoader(AbstractGenericContextLoader).loadContext(String...) line: 84	
GenericXmlContextLoader(AbstractGenericContextLoader).loadContext(String...) line: 1	
TestContext.loadApplicationContext() line: 280	
TestContext.getApplicationContext() line: 304	
DependencyInjectionTestExecutionListener.injectDependencies(TestContext) line: 109	
DependencyInjectionTestExecutionListener.prepareTestInstance(TestContext) line: 75	
TestContextManager.prepareTestInstance(Object) line: 333	
SpringJUnit4ClassRunner.createTest() line: 220	
SpringJUnit4ClassRunner$1.runReflectiveCall() line: 301	
SpringJUnit4ClassRunner$1(ReflectiveCallable).run() line: 15	
SpringJUnit4ClassRunner.methodBlock(FrameworkMethod) line: 303	
SpringJUnit4ClassRunner.runChild(FrameworkMethod, RunNotifier) line: 240	
SpringJUnit4ClassRunner(BlockJUnit4ClassRunner).runChild(Object, RunNotifier) line: 50	
ParentRunner$3.run() line: 193	
ParentRunner$1.schedule(Runnable) line: 52	
SpringJUnit4ClassRunner(ParentRunner<T>).runChildren(RunNotifier) line: 191	
ParentRunner<T>.access$000(ParentRunner, RunNotifier) line: 42	
ParentRunner$2.evaluate() line: 184	
RunBeforeTestClassCallbacks.evaluate() line: 61	
RunAfterTestClassCallbacks.evaluate() line: 70	
SpringJUnit4ClassRunner(ParentRunner<T>).run(RunNotifier) line: 236	
SpringJUnit4ClassRunner.run(RunNotifier) line: 180	
JUnit4TestClassReference(JUnit4TestReference).run(TestExecution) line: 46	
TestExecution.run(ITestReference[]) line: 38	
RemoteTestRunner.runTests(String[], String, TestExecution) line: 467	
RemoteTestRunner.runTests(TestExecution) line: 683	
RemoteTestRunner.run() line: 390	
RemoteTestRunner.main(String[]) line: 197	

Am I missing something, is it impossible to use generic events (as designed) or is it a bug?

Thanks,
Marek.

[spring-projects-issues]

Juergen Hoeller commented

This should be fixed in 3.0.4 already (see #12047). Please give one of the latest 3.0.4 snapshots a try and let us know whether it works for you...

Juergen

[spring-projects-issues]

Marek Romanowski commented

I've downloaded latest trunk and it works correctly for me. I'm not sure, but I think one more thing is wrong. After adding code below to GenericTypeResolverTests I get one more correct test. But it means that GenericApplicationListenerAdapter.supportsEventType will accept all objects for listeners with generic declaration similar to MyDoubleBoundedType. MyDoubleBoundedType accepts only MyInterfaceType subclasses. I know it won't be common case, but it is legal java syntax after all. Problem is that a) GenericTypeResolver.extractBoundForTypeVariable checks only first bound from generic type and b) GenericTypeResolver.resolveTypeArgument returns one Class as a result.

@Test
public void testDoubleBoundedType() {
	assertEquals(Object.class, GenericTypeResolver.resolveTypeArgument(MyDoubleBoundedType.class, MySuperclassType.class));
}
public class MyDoubleBoundedType<E extends Object & MyInterfaceType> extends MySuperclassType<E> {
}