Add ResolvableTypeProvider

Provide a mean to detect the actual ResolvableType based on a instance as
a counter measure to type erasure.

Upgrade the event infrastructure to detect if the event (or the payload)
implements such interface. When this is the case, the return value of
`getResolvableType` is used to validate its generic type against the
method signature of the listener.

Issue: SPR-13069

spring-context/src/main/java/org/springframework/context/PayloadApplicationEvent.java

@@ -16,6 +16,8 @@
 
 package org.springframework.context;
 
+import org.springframework.core.ResolvableType;
+import org.springframework.core.ResolvableTypeProvider;
 import org.springframework.util.Assert;
 
 /**
@@ -28,7 +30,7 @@ import org.springframework.util.Assert;
  * @param <T> the payload type of the event
  */
 @SuppressWarnings("serial")
-public class PayloadApplicationEvent<T> extends ApplicationEvent {
+public class PayloadApplicationEvent<T> extends ApplicationEvent implements ResolvableTypeProvider {
 
 	private final T payload;
 
@@ -44,6 +46,11 @@ public class PayloadApplicationEvent<T> extends ApplicationEvent {
 		this.payload = payload;
 	}
 
+	@Override
+	public ResolvableType getResolvableType() {
+		return ResolvableType.forClassWithGenerics(getClass(),
+				ResolvableType.forInstance(getPayload()));
+	}
 
 	/**
 	 * Return the payload of the event.

spring-context/src/main/java/org/springframework/context/event/ApplicationListenerMethodAdapter.java

@@ -124,10 +124,11 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 	protected Object[] resolveArguments(ApplicationEvent event) {
 		if (!ApplicationEvent.class.isAssignableFrom(this.declaredEventType.getRawClass())
 				&& event instanceof PayloadApplicationEvent) {
-			@SuppressWarnings("rawtypes")
-			Object payload = ((PayloadApplicationEvent) event).getPayload();
-			if (this.declaredEventType.isAssignableFrom(ResolvableType.forClass(payload.getClass()))) {
-				return new Object[] {payload};
+			PayloadApplicationEvent<?> payloadEvent = (PayloadApplicationEvent<?>) event;
+			ResolvableType payloadType =  payloadEvent.getResolvableType()
+					.as(PayloadApplicationEvent.class).getGeneric(0);
+			if (this.declaredEventType.isAssignableFrom(payloadType)) {
+				return new Object[] {payloadEvent.getPayload()};
 			}
 		}
 		else {

spring-context/src/main/java/org/springframework/context/event/SimpleApplicationEventMulticaster.java

@@ -139,7 +139,7 @@ public class SimpleApplicationEventMulticaster extends AbstractApplicationEventM
 	}
 
 	private ResolvableType resolveDefaultEventType(ApplicationEvent event) {
-		return ResolvableType.forType(event.getClass());
+		return ResolvableType.forInstance(event);
 	}
 
 	/**