GenericApplicationListenerAdapter caches resolved event types

Issue: SPR-16970

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,13 +16,16 @@
 
 package org.springframework.context.event;
 
+import java.util.Map;
+
 import org.springframework.aop.support.AopUtils;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.core.Ordered;
 import org.springframework.core.ResolvableType;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.ConcurrentReferenceHashMap;
 
 /**
  * {@link GenericApplicationListener} adapter that determines supported event types
@@ -35,6 +38,9 @@
  */
 public class GenericApplicationListenerAdapter implements GenericApplicationListener, SmartApplicationListener {
 
+	private static final Map<Class<?>, ResolvableType> eventTypeCache = new ConcurrentReferenceHashMap<>();
+
+
 	private final ApplicationListener<ApplicationEvent> delegate;
 
 	@Nullable
@@ -86,17 +92,11 @@ public int getOrder() {
 		return (this.delegate instanceof Ordered ? ((Ordered) this.delegate).getOrder() : Ordered.LOWEST_PRECEDENCE);
 	}
 
-	@Nullable
-	static ResolvableType resolveDeclaredEventType(Class<?> listenerType) {
-		ResolvableType resolvableType = ResolvableType.forClass(listenerType).as(ApplicationListener.class);
-		return (resolvableType.hasGenerics() ? resolvableType.getGeneric() : null);
-	}
 
 	@Nullable
 	private static ResolvableType resolveDeclaredEventType(ApplicationListener<ApplicationEvent> listener) {
 		ResolvableType declaredEventType = resolveDeclaredEventType(listener.getClass());
-		if (declaredEventType == null || declaredEventType.isAssignableFrom(
-				ResolvableType.forClass(ApplicationEvent.class))) {
+		if (declaredEventType == null || declaredEventType.isAssignableFrom(ApplicationEvent.class)) {
 			Class<?> targetClass = AopUtils.getTargetClass(listener);
 			if (targetClass != listener.getClass()) {
 				declaredEventType = resolveDeclaredEventType(targetClass);
@@ -105,4 +105,14 @@ private static ResolvableType resolveDeclaredEventType(ApplicationListener<Appli
 		return declaredEventType;
 	}
 
+	@Nullable
+	static ResolvableType resolveDeclaredEventType(Class<?> listenerType) {
+		ResolvableType eventType = eventTypeCache.get(listenerType);
+		if (eventType == null) {
+			eventType = ResolvableType.forClass(listenerType).as(ApplicationListener.class).getGeneric();
+			eventTypeCache.put(listenerType, eventType);
+		}
+		return (eventType != ResolvableType.NONE ? eventType : null);
+	}
+
 }

spring-context/src/test/java/org/springframework/context/event/AbstractApplicationEventListenerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,13 +33,13 @@ protected ResolvableType getGenericApplicationEventType(String fieldName) {
 		try {
 			return ResolvableType.forField(TestEvents.class.getField(fieldName));
 		}
-		catch (NoSuchFieldException e) {
+		catch (NoSuchFieldException ex) {
 			throw new IllegalStateException("No such field on Events '" + fieldName + "'");
 		}
 	}
 
-	protected static class GenericTestEvent<T>
-			extends ApplicationEvent {
+
+	protected static class GenericTestEvent<T> extends ApplicationEvent {
 
 		private final T payload;
 
@@ -51,11 +51,9 @@ public GenericTestEvent(Object source, T payload) {
 		public T getPayload() {
 			return this.payload;
 		}
-
 	}
 
-	protected static class SmartGenericTestEvent<T>
-			extends GenericTestEvent<T> implements ResolvableTypeProvider {
+	protected static class SmartGenericTestEvent<T> extends GenericTestEvent<T> implements ResolvableTypeProvider {
 
 		private final ResolvableType resolvableType;
 
@@ -119,6 +117,7 @@ public void onApplicationEvent(GenericTestEvent<String> event) {
 
 	@SuppressWarnings("rawtypes")
 	static class RawApplicationListener implements ApplicationListener {
+
 		@Override
 		public void onApplicationEvent(ApplicationEvent event) {
 		}
@@ -137,7 +136,6 @@ static class TestEvents {
 		public GenericTestEvent<IllegalStateException> illegalStateExceptionEvent;
 
 		public GenericTestEvent<IOException> ioExceptionEvent;
-
 	}
 
 }

spring-context/src/test/java/org/springframework/context/event/ApplicationContextEventTests.java

@@ -63,6 +63,8 @@ public class ApplicationContextEventTests extends AbstractApplicationEventListen
 
 	@Test
 	public void multicastSimpleEvent() {
+		multicastEvent(true, ApplicationListener.class,
+				new ContextRefreshedEvent(new StaticApplicationContext()), null);
 		multicastEvent(true, ApplicationListener.class,
 				new ContextClosedEvent(new StaticApplicationContext()), null);
 	}

spring-context/src/test/java/org/springframework/context/event/GenericApplicationListenerAdapterTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -100,8 +100,7 @@ public void genericListenerStrictTypeNotMatchTypeErasure() {
 
 	@Test
 	public void genericListenerStrictTypeSubClass() {
-		supportsEventType(false, ObjectEventListener.class,
-				getGenericApplicationEventType("longEvent"));
+		supportsEventType(false, ObjectEventListener.class, getGenericApplicationEventType("longEvent"));
 	}
 
 	@Test
@@ -111,7 +110,7 @@ public void genericListenerUpperBoundType() {
 	}
 
 	@Test
-	public void genericListenerUpperBoundTypeNotMatching() throws NoSuchFieldException {
+	public void genericListenerUpperBoundTypeNotMatching() {
 		supportsEventType(false, UpperBoundEventListener.class,
 				getGenericApplicationEventType("ioExceptionEvent"));
 	}
@@ -142,8 +141,9 @@ public void genericListenerRawTypeTypeErasure() {
 		supportsEventType(true, RawApplicationListener.class, eventType);
 	}
 
-	private void supportsEventType(boolean match, Class<? extends ApplicationListener> listenerType,
-			ResolvableType eventType) {
+
+	private void supportsEventType(
+			boolean match, Class<? extends ApplicationListener> listenerType, ResolvableType eventType) {
 
 		ApplicationListener<?> listener = mock(listenerType);
 		GenericApplicationListenerAdapter adapter = new GenericApplicationListenerAdapter(listener);