Clarify event parameter type for multiple mapped classes

Closes gh-35506

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

@@ -101,10 +101,9 @@ public @interface EventListener {
 
 	/**
 	 * The event classes that this listener handles.
-	 * <p>If this attribute is specified with a single value, the
-	 * annotated method may optionally accept a single parameter.
-	 * However, if this attribute is specified with multiple values,
-	 * the annotated method must <em>not</em> declare any parameters.
+	 * <p>The annotated method may optionally accept a single parameter
+	 * of the given event class, or of a common base class or interface
+	 * for all given event classes.
 	 */
 	@AliasFor("value")
 	Class<?>[] classes() default {};

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

@@ -16,6 +16,7 @@
 
 package org.springframework.context.event;
 
+import java.io.Serializable;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -105,8 +106,9 @@ class AnnotationDrivenEventListenerTests {
 		this.eventCollector.assertTotalEventsCount(1);
 
 		this.eventCollector.clear();
-		this.context.publishEvent(event);
-		this.eventCollector.assertEvent(listener, event);
+		TestEvent otherEvent = new TestEvent(this, Integer.valueOf(1));
+		this.context.publishEvent(otherEvent);
+		this.eventCollector.assertEvent(listener, otherEvent);
 		this.eventCollector.assertTotalEventsCount(1);
 
 		context.getBean(ApplicationEventMulticaster.class).removeApplicationListeners(l ->
@@ -742,6 +744,11 @@ class AnnotationDrivenEventListenerTests {
 		public void handleString(String content) {
 			collectEvent(content);
 		}
+
+		@EventListener({Boolean.class, Integer.class})
+		public void handleBooleanOrInteger(Serializable content) {
+			collectEvent(content);
+		}
 	}
 
 
@@ -1009,6 +1016,8 @@ class AnnotationDrivenEventListenerTests {
 
 		void handleString(String payload);
 
+		void handleBooleanOrInteger(Serializable content);
+
 		void handleTimestamp(Long timestamp);
 
 		void handleRatio(Double ratio);
@@ -1031,6 +1040,12 @@ class AnnotationDrivenEventListenerTests {
 			super.handleString(payload);
 		}
 
+		@EventListener({Boolean.class, Integer.class})
+		@Override
+		public void handleBooleanOrInteger(Serializable content) {
+			super.handleBooleanOrInteger(content);
+		}
+
 		@ConditionalEvent("#root.event.timestamp > #p0")
 		@Override
 		public void handleTimestamp(Long timestamp) {

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

@@ -18,11 +18,12 @@ package org.springframework.context.event.test;
 
 /**
  * @author Stephane Nicoll
+ * @author Juergen Hoeller
  */
 @SuppressWarnings("serial")
 public class TestEvent extends IdentifiableApplicationEvent {
 
-	public final String msg;
+	public final Object msg;
 
 	public TestEvent(Object source, String id, String msg) {
 		super(source, id);
@@ -34,6 +35,11 @@ public class TestEvent extends IdentifiableApplicationEvent {
 		this.msg = msg;
 	}
 
+	public TestEvent(Object source, Integer msg) {
+		super(source);
+		this.msg = msg;
+	}
+
 	public TestEvent(Object source) {
 		this(source, "test");
 	}