Support for multiple events per method

In addition to specifying the event type to listen to via a method
parameter, any @EventListener annotated method can now alternatively
define the event type(s) to listen to via the "classes" attributes (that
is aliased to "value").

Something like

@EventListener({FooEvent.class, BarEvent.class})
public void handleFooBar() { .... }

Issue: SPR-13156

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

@@ -20,7 +20,10 @@ import java.lang.annotation.Annotation;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.UndeclaredThrowableException;
+import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -66,7 +69,7 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 
 	private final Method bridgedMethod;
 
-	private final ResolvableType declaredEventType;
+	private final List<ResolvableType> declaredEventTypes;
 
 	private final AnnotatedElementKey methodKey;
 
@@ -76,12 +79,14 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 
 	private String condition;
 
+	private EventListener eventListener;
+
 	public ApplicationListenerMethodAdapter(String beanName, Class<?> targetClass, Method method) {
 		this.beanName = beanName;
 		this.method = method;
 		this.targetClass = targetClass;
 		this.bridgedMethod = BridgeMethodResolver.findBridgedMethod(method);
-		this.declaredEventType = resolveDeclaredEventType();
+		this.declaredEventTypes = resolveDeclaredEventTypes();
 		this.methodKey = new AnnotatedElementKey(this.method, this.targetClass);
 	}
 
@@ -122,19 +127,20 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 	 * therefore the method should not be invoked at all for the specified event.
 	 */
 	protected Object[] resolveArguments(ApplicationEvent event) {
-		if (!ApplicationEvent.class.isAssignableFrom(this.declaredEventType.getRawClass())
+		ResolvableType declaredEventType = getResolvableType(event);
+		if (declaredEventType == null) {
+			return null;
+		}
+		if (this.method.getParameters().length == 0) {
+			return new Object[0];
+		}
+		if (!ApplicationEvent.class.isAssignableFrom(declaredEventType.getRawClass())
 				&& event instanceof PayloadApplicationEvent) {
-			PayloadApplicationEvent<?> payloadEvent = (PayloadApplicationEvent<?>) event;
-			ResolvableType payloadType =  payloadEvent.getResolvableType()
-					.as(PayloadApplicationEvent.class).getGeneric(0);
-			if (this.declaredEventType.isAssignableFrom(payloadType)) {
-				return new Object[] {payloadEvent.getPayload()};
-			}
+			return new Object[] {((PayloadApplicationEvent) event).getPayload()};
 		}
 		else {
 			return new Object[] {event};
 		}
-		return null;
 	}
 
 	protected void handleResult(Object result) {
@@ -178,14 +184,18 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 
 	@Override
 	public boolean supportsEventType(ResolvableType eventType) {
-		if (this.declaredEventType.isAssignableFrom(eventType)) {
-			return true;
+		for (ResolvableType declaredEventType : this.declaredEventTypes) {
+			if (declaredEventType.isAssignableFrom(eventType)) {
+				return true;
+			}
+			else if (PayloadApplicationEvent.class.isAssignableFrom(eventType.getRawClass())) {
+				ResolvableType payloadType = eventType.as(PayloadApplicationEvent.class).getGeneric();
+				if (declaredEventType.isAssignableFrom(payloadType)) {
+					return true;
+				}
+			}
 		}
-		else if (PayloadApplicationEvent.class.isAssignableFrom(eventType.getRawClass())) {
-			ResolvableType payloadType = eventType.as(PayloadApplicationEvent.class).getGeneric();
-			return eventType.hasUnresolvableGenerics() || this.declaredEventType.isAssignableFrom(payloadType);
-		}
-		return false;
+		return eventType.hasUnresolvableGenerics();
 	}
 
 	@Override
@@ -240,6 +250,13 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 		return this.applicationContext.getBean(this.beanName);
 	}
 
+	protected EventListener getEventListener() {
+		if (this.eventListener == null) {
+			this.eventListener = AnnotatedElementUtils.findMergedAnnotation(this.method, EventListener.class);
+		}
+		return this.eventListener;
+	}
+
 	/**
 	 * Return the condition to use.
 	 * <p>Matches the {@code condition} attribute of the {@link EventListener}
@@ -305,13 +322,48 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 	}
 
 
-	private ResolvableType resolveDeclaredEventType() {
+	private ResolvableType getResolvableType(ApplicationEvent event) {
+		ResolvableType payloadType = null;
+		if (event instanceof PayloadApplicationEvent) {
+			PayloadApplicationEvent<?> payloadEvent = (PayloadApplicationEvent<?>) event;
+			payloadType = payloadEvent.getResolvableType().as(
+					PayloadApplicationEvent.class).getGeneric(0);
+		}
+		for (ResolvableType declaredEventType : this.declaredEventTypes) {
+			if (!ApplicationEvent.class.isAssignableFrom(declaredEventType.getRawClass())
+					&& payloadType != null) {
+				if (declaredEventType.isAssignableFrom(payloadType)) {
+					return declaredEventType;
+				}
+			}
+			if (declaredEventType.getRawClass().isAssignableFrom(event.getClass())) {
+				return declaredEventType;
+			}
+		}
+		return null;
+	}
+
+	private List<ResolvableType> resolveDeclaredEventTypes() {
 		int count = this.method.getParameterTypes().length;
-		if (count != 1) {
-			throw new IllegalStateException("Only one parameter is allowed " +
+		if (count > 1) {
+			throw new IllegalStateException("Maximum one parameter is allowed " +
 					"for event listener method: " + method);
 		}
-		return ResolvableType.forMethodParameter(this.method, 0);
+		EventListener ann = getEventListener();
+		if (ann != null && ann.classes().length > 0) {
+			List<ResolvableType> types = new ArrayList<ResolvableType>();
+			for (Class<?> eventType : ann.classes()) {
+				types.add(ResolvableType.forClass(eventType));
+			}
+			return types;
+		}
+		else {
+			if (count == 0) {
+				throw new IllegalStateException("Event parameter is mandatory " +
+						"for event listener method: " + method);
+			}
+			return Collections.singletonList(ResolvableType.forMethodParameter(this.method, 0));
+		}
 	}
 
 	@Override

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

@@ -23,12 +23,14 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.context.ApplicationEvent;
+import org.springframework.core.annotation.AliasFor;
 
 /**
  * Annotation that marks a method to listen for application events. The
- * method should have one and only one parameter that reflects the event
- * type to listen to. Events can be {@link ApplicationEvent} instances
- * as well as arbitrary objects.
+ * method may have one (and only one) parameter that reflects the event
+ * type to listen to. Or this annotation may refer to the event type(s)
+ * using the {@link #classes()} attribute. Events can be {@link ApplicationEvent}
+ * instances as well as arbitrary objects.
  *
  * <p>Processing of {@code @EventListener} annotations is performed via
  * {@link EventListenerMethodProcessor} that is registered automatically
@@ -54,6 +56,21 @@ import org.springframework.context.ApplicationEvent;
 @Documented
 public @interface EventListener {
 
+	/**
+	 * Alias for {@link #classes()}.
+	 */
+	@AliasFor(attribute = "classes")
+	Class<?>[] value() default {};
+
+	/**
+	 * The event classes that this listener handles. When this attribute is specified
+	 * with one value, the method parameter may or may not be specified. When this
+	 * attribute is specified with more than one value, the method must not have a
+	 * parameter.
+	 */
+	@AliasFor(attribute = "value")
+	Class<?>[] classes() default {};
+
 	/**
 	 * Spring Expression Language (SpEL) attribute used for making the event
 	 * handling conditional.

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

@@ -113,6 +113,36 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		supportsEventType(true, method, ResolvableType.forClass(PayloadStringTestEvent.class));
 	}
 
+	@Test
+	public void listenerWithAnnotationValue() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringAnnotationValue");
+		supportsEventType(true, method, createGenericEventType(String.class));
+	}
+
+	@Test
+	public void listenerWithAnnotationClasses() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringAnnotationClasses");
+		supportsEventType(true, method, createGenericEventType(String.class));
+	}
+
+	@Test
+	public void listenerWithAnnotationValueAndParameter() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringAnnotationValueAndParameter", String.class);
+		supportsEventType(true, method, createGenericEventType(String.class));
+	}
+
+	@Test
+	public void listenerWithSeveralTypes() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringOrInteger");
+		supportsEventType(true, method, createGenericEventType(String.class));
+		supportsEventType(true, method, createGenericEventType(Integer.class));
+		supportsEventType(false, method, createGenericEventType(Double.class));
+	}
+
 	@Test
 	public void listenerWithTooManyParameters() {
 		Method method = ReflectionUtils.findMethod(SampleEvents.class,
@@ -131,6 +161,15 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		createTestInstance(method);
 	}
 
+	@Test
+	public void listenerWithMoreThanOneParameter() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"moreThanOneParameter", String.class, Integer.class);
+
+		thrown.expect(IllegalStateException.class);
+		createTestInstance(method);
+	}
+
 	@Test
 	public void defaultOrder() {
 		Method method = ReflectionUtils.findMethod(SampleEvents.class,
@@ -249,6 +288,40 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		verify(this.sampleEvents, never()).handleString(anyString());
 	}
 
+	@Test
+	public void invokeListenerWithAnnotationValue() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringAnnotationClasses");
+		PayloadApplicationEvent<String> event = new PayloadApplicationEvent<>(this, "test");
+		invokeListener(method, event);
+		verify(this.sampleEvents, times(1)).handleStringAnnotationClasses();
+	}
+
+	@Test
+	public void invokeListenerWithAnnotationValueAndParameter() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringAnnotationValueAndParameter", String.class);
+		PayloadApplicationEvent<String> event = new PayloadApplicationEvent<>(this, "test");
+		invokeListener(method, event);
+		verify(this.sampleEvents, times(1)).handleStringAnnotationValueAndParameter("test");
+	}
+
+	@Test
+	public void invokeListenerWithSeveralTypes() {
+		Method method = ReflectionUtils.findMethod(SampleEvents.class,
+				"handleStringOrInteger");
+		PayloadApplicationEvent<String> event = new PayloadApplicationEvent<>(this, "test");
+		invokeListener(method, event);
+		verify(this.sampleEvents, times(1)).handleStringOrInteger();
+		PayloadApplicationEvent<Integer> event2 = new PayloadApplicationEvent<>(this, 123);
+		invokeListener(method, event2);
+		verify(this.sampleEvents, times(2)).handleStringOrInteger();
+		PayloadApplicationEvent<Double> event3 = new PayloadApplicationEvent<>(this, 23.2);
+		invokeListener(method, event3);
+		verify(this.sampleEvents, times(2)).handleStringOrInteger();
+	}
+
+
 	@Test
 	public void beanInstanceRetrievedAtEveryInvocation() {
 		Method method = ReflectionUtils.findMethod(SampleEvents.class,
@@ -321,14 +394,32 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		public void handleString(String payload) {
 		}
 
+		@EventListener(String.class)
+		public void handleStringAnnotationValue() {
+		}
+
+		@EventListener(classes = String.class)
+		public void handleStringAnnotationClasses() {
+		}
+
+		@EventListener(String.class)
+		public void handleStringAnnotationValueAndParameter(String payload) {
+		}
+
+		@EventListener({String.class, Integer.class})
+		public void handleStringOrInteger() {
+		}
+
+		@EventListener({String.class, Integer.class})
+		public void handleStringOrIntegerWithParam(String invalid) {
+		}
+
 		@EventListener
 		public void handleGenericStringPayload(EntityWrapper<String> event) {
-
 		}
 
 		@EventListener
 		public void handleGenericAnyPayload(EntityWrapper<?> event) {
-
 		}
 
 		@EventListener
@@ -339,6 +430,10 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		public void noParameter() {
 		}
 
+		@EventListener
+		public void moreThanOneParameter(String foo, Integer bar) {
+		}
+
 		@EventListener
 		public void generateRuntimeException(GenericTestEvent<String> event) {
 			if ("fail".equals(event.getPayload())) {

spring-tx/src/main/java/org/springframework/transaction/event/ApplicationListenerMethodTransactionalAdapter.java

@@ -25,7 +25,7 @@ import org.springframework.context.ApplicationEvent;
 import org.springframework.context.event.ApplicationListenerMethodAdapter;
 import org.springframework.context.event.EventListener;
 import org.springframework.context.event.GenericApplicationListener;
-import org.springframework.core.annotation.AnnotationUtils;
+import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.transaction.support.TransactionSynchronization;
 import org.springframework.transaction.support.TransactionSynchronizationAdapter;
 import org.springframework.transaction.support.TransactionSynchronizationManager;
@@ -80,8 +80,8 @@ class ApplicationListenerMethodTransactionalAdapter extends ApplicationListenerM
 	}
 
 	static TransactionalEventListener findAnnotation(Method method) {
-		TransactionalEventListener annotation = AnnotationUtils
-				.findAnnotation(method, TransactionalEventListener.class);
+		TransactionalEventListener annotation = AnnotatedElementUtils
+				.findMergedAnnotation(method, TransactionalEventListener.class);
 		if (annotation == null) {
 			throw new IllegalStateException("No TransactionalEventListener annotation found on '" + method + "'");
 		}

spring-tx/src/main/java/org/springframework/transaction/event/TransactionalEventListener.java

@@ -23,6 +23,7 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 import org.springframework.context.event.EventListener;
+import org.springframework.core.annotation.AliasFor;
 
 /**
  * An {@link EventListener} that is invoked according to a {@link TransactionPhase}.
@@ -55,6 +56,21 @@ public @interface TransactionalEventListener {
 	 */
 	boolean fallbackExecution() default false;
 
+	/**
+	 * Alias for {@link #classes()}.
+	 */
+	@AliasFor(attribute = "classes")
+	Class<?>[] value() default {};
+
+	/**
+	 * The event classes that this listener handles. When this attribute is specified
+	 * with one value, the method parameter may or may not be specified. When this
+	 * attribute is specified with more than one value, the method must not have a
+	 * parameter.
+	 */
+	@AliasFor(attribute = "value")
+	Class<?>[] classes() default {};
+
 	/**
 	 * Spring Expression Language (SpEL) attribute used for making the event
 	 * handling conditional.

spring-tx/src/test/java/org/springframework/transaction/event/ApplicationListenerMethodTransactionalAdapterTests.java

@@ -22,6 +22,9 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import org.springframework.context.PayloadApplicationEvent;
+import org.springframework.context.event.ApplicationListenerMethodAdapter;
+import org.springframework.core.ResolvableType;
 import org.springframework.util.ReflectionUtils;
 
 import static org.junit.Assert.*;
@@ -36,7 +39,7 @@ public class ApplicationListenerMethodTransactionalAdapterTests {
 
 	@Test
 	public void noAnnotation() {
-		Method m = ReflectionUtils.findMethod(PhaseConfigurationTestListener.class,
+		Method m = ReflectionUtils.findMethod(SampleEvents.class,
 				"noAnnotation", String.class);
 
 		thrown.expect(IllegalStateException.class);
@@ -46,24 +49,54 @@ public class ApplicationListenerMethodTransactionalAdapterTests {
 
 	@Test
 	public void defaultPhase() {
-		Method m = ReflectionUtils.findMethod(PhaseConfigurationTestListener.class, "defaultPhase", String.class);
+		Method m = ReflectionUtils.findMethod(SampleEvents.class, "defaultPhase", String.class);
 		assertPhase(m, TransactionPhase.AFTER_COMMIT);
 	}
 
 	@Test
 	public void phaseSet() {
-		Method m = ReflectionUtils.findMethod(PhaseConfigurationTestListener.class, "phaseSet", String.class);
+		Method m = ReflectionUtils.findMethod(SampleEvents.class, "phaseSet", String.class);
 		assertPhase(m, TransactionPhase.AFTER_ROLLBACK);
 	}
 
+	@Test
+	public void phaseAndClassesSet() {
+		Method m = ReflectionUtils.findMethod(SampleEvents.class, "phaseAndClassesSet");
+		assertPhase(m, TransactionPhase.AFTER_COMPLETION);
+		supportsEventType(true, m, createGenericEventType(String.class));
+		supportsEventType(true, m, createGenericEventType(Integer.class));
+		supportsEventType(false, m, createGenericEventType(Double.class));
+	}
+
+	@Test
+	public void valueSet() {
+		Method m = ReflectionUtils.findMethod(SampleEvents.class, "valueSet");
+		assertPhase(m, TransactionPhase.AFTER_COMMIT);
+		supportsEventType(true, m, createGenericEventType(String.class));
+		supportsEventType(false, m, createGenericEventType(Double.class));
+	}
+
 	private void assertPhase(Method method, TransactionPhase expected) {
 		assertNotNull("Method must not be null", method);
 		TransactionalEventListener annotation = ApplicationListenerMethodTransactionalAdapter.findAnnotation(method);
 		assertEquals("Wrong phase for '" + method + "'", expected, annotation.phase());
 	}
 
+	private void supportsEventType(boolean match, Method method, ResolvableType eventType) {
+		ApplicationListenerMethodAdapter adapter = createTestInstance(method);
+		assertEquals("Wrong match for event '" + eventType + "' on " + method,
+				match, adapter.supportsEventType(eventType));
+	}
 
-	static class PhaseConfigurationTestListener {
+	private ApplicationListenerMethodTransactionalAdapter createTestInstance(Method m) {
+		return new ApplicationListenerMethodTransactionalAdapter("test", SampleEvents.class, m);
+	}
+
+	private ResolvableType createGenericEventType(Class<?> payloadType) {
+		return ResolvableType.forClassWithGenerics(PayloadApplicationEvent.class, payloadType);
+	}
+
+	static class SampleEvents {
 
 		public void noAnnotation(String data) {
 		}
@@ -76,6 +109,15 @@ public class ApplicationListenerMethodTransactionalAdapterTests {
 		public void phaseSet(String data) {
 		}
 
+		@TransactionalEventListener(classes = {String.class, Integer.class},
+				phase = TransactionPhase.AFTER_COMPLETION)
+		public void phaseAndClassesSet() {
+		}
+
+		@TransactionalEventListener(String.class)
+		public void valueSet() {
+		}
+
 	}
 
 }

src/asciidoc/core-beans.adoc

@@ -7900,6 +7900,19 @@ As you can see above, the method signature actually _infer_ which even type it l
 also works for nested generics as long as the actual event resolves the generics parameter you
 would filter on.
 
+If your method should listen to several events or if you want to define it with no
+parameter at all, the event type(s) can also be specified on the annotation itself:
+
+[source,java,indent=0]
+[subs="verbatim,quotes"]
+----
+	@EventListener({ContextStartedEvent.class, ContextRefreshedEvent.class})
+	public void handleContextStart() {
+
+	}
+----
+
+
 It is also possible to add additional runtime filtering via the `condition` attribute of the
 annotation that defines a <<expressions,`SpEL` expression>> that should match to actually invoke
 the method for a particular event.