Polish "Add support for explicit generic type in PayloadApplicationEvent"

See gh-24599

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

@@ -39,17 +39,7 @@ public class PayloadApplicationEvent<T> extends ApplicationEvent implements Reso
 
 	private final T payload;
 
-	@Nullable
+	private final ResolvableType payloadType;
-	private ResolvableType payloadType;
-
-	/**
-	 * Create a new PayloadApplicationEvent.
-	 * @param source the object on which the event initially occurred (never {@code null})
-	 * @param payload the payload object (never {@code null})
-	 */
-	public PayloadApplicationEvent(Object source, T payload) {
-		this(source, payload, null);
-	}
 
 	/**
 	 * Create a new PayloadApplicationEvent.
@@ -61,15 +51,21 @@ public class PayloadApplicationEvent<T> extends ApplicationEvent implements Reso
 		super(source);
 		Assert.notNull(payload, "Payload must not be null");
 		this.payload = payload;
-		this.payloadType = payloadType;
+		this.payloadType = (payloadType != null) ? payloadType : ResolvableType.forInstance(payload);
+	}
+
+	/**
+	 * Create a new PayloadApplicationEvent, using the instance to infer its type.
+	 * @param source the object on which the event initially occurred (never {@code null})
+	 * @param payload the payload object (never {@code null})
+	 */
+	public PayloadApplicationEvent(Object source, T payload) {
+		this(source, payload, null);
 	}
 
 
 	@Override
 	public ResolvableType getResolvableType() {
-		if (this.payloadType == null) {
-			this.payloadType = ResolvableType.forInstance(getPayload());
-		}
 		return ResolvableType.forClassWithGenerics(getClass(), this.payloadType);
 	}
 

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

@@ -60,7 +60,6 @@ import org.springframework.context.event.test.GenericEventPojo;
 import org.springframework.context.event.test.Identifiable;
 import org.springframework.context.event.test.TestEvent;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
-import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AliasFor;
 import org.springframework.core.annotation.Order;
 import org.springframework.scheduling.annotation.Async;
@@ -623,17 +622,6 @@ class AnnotationDrivenEventListenerTests {
 		this.eventCollector.assertNoEventReceived(listener);
 		this.eventCollector.assertTotalEventsCount(0);
 	}
-	@Test
-	public void publishEventWithGeneric() throws NoSuchMethodException {
-		MyAnnotationConfigApplicationContext ctx = new MyAnnotationConfigApplicationContext();
-		context = ctx;
-		ctx.register(MyEventWithGenericListener.class);
-		ctx.refresh();
-		ResolvableType resolvableType = ResolvableType.forMethodParameter(MyEventWithGenericListener.class.getMethod("onMyEventWithGeneric",MyEventWithGeneric.class),0);
-		ctx.publishEvent(new MyEventWithGeneric<String>(),resolvableType);
-		assertThat(MyEventWithGenericListener.count).isEqualTo(1);
-	}
-
 
 	@Test
 	void orderedListeners() {
@@ -1146,29 +1134,4 @@ class AnnotationDrivenEventListenerTests {
 		}
 	}
 
-	public static class MyAnnotationConfigApplicationContext extends AnnotationConfigApplicationContext{
-
-		@Override
-		public void publishEvent(Object event, ResolvableType eventType) {
-			super.publishEvent(event, eventType);
-		}
-	}
-
-	public static class MyEventWithGeneric<T> {
-
-	}
-
-	@Component
-	public static class MyEventWithGenericListener{
-
-		public static int count ;
-
-		@EventListener
-		public void onMyEventWithGeneric(MyEventWithGeneric<String> event){
-			count ++;
-		}
-
-
-	}
-
 }

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

@@ -27,6 +27,7 @@ import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.PayloadApplicationEvent;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.support.GenericApplicationContext;
+import org.springframework.core.ResolvableType;
 import org.springframework.stereotype.Component;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -34,10 +35,40 @@ import static org.assertj.core.api.Assertions.assertThat;
 /**
  * @author Juergen Hoeller
  */
-public class PayloadApplicationEventTests {
+class PayloadApplicationEventTests {
 
 	@Test
-	public void testEventClassWithInterface() {
+	void payloadApplicationEventWithNoTypeUsesInstance() {
+		NumberHolder<Integer> payload = new NumberHolder<>(42);
+		PayloadApplicationEvent<NumberHolder<Integer>> event = new PayloadApplicationEvent<>(this, payload);
+		assertThat(event.getResolvableType()).satisfies(eventType -> {
+			assertThat(eventType.toClass()).isEqualTo(PayloadApplicationEvent.class);
+			assertThat(eventType.getGenerics()).hasSize(1);
+			assertThat(eventType.getGenerics()[0]).satisfies(bodyType -> {
+				assertThat(bodyType.toClass()).isEqualTo(NumberHolder.class);
+				assertThat(bodyType.hasUnresolvableGenerics()).isTrue();
+			});
+		});
+	}
+
+	@Test
+	void payloadApplicationEventWithType() {
+		NumberHolder<Integer> payload = new NumberHolder<>(42);
+		ResolvableType payloadType = ResolvableType.forClassWithGenerics(NumberHolder.class, Integer.class);
+		PayloadApplicationEvent<NumberHolder<Integer>> event = new PayloadApplicationEvent<>(this, payload, payloadType);
+		assertThat(event.getResolvableType()).satisfies(eventType -> {
+			assertThat(eventType.toClass()).isEqualTo(PayloadApplicationEvent.class);
+			assertThat(eventType.getGenerics()).hasSize(1);
+			assertThat(eventType.getGenerics()[0]).satisfies(bodyType -> {
+				assertThat(bodyType.toClass()).isEqualTo(NumberHolder.class);
+				assertThat(bodyType.hasUnresolvableGenerics()).isFalse();
+				assertThat(bodyType.getGenerics()[0].toClass()).isEqualTo(Integer.class);
+			});
+		});
+	}
+
+	@Test
+	void testEventClassWithInterface() {
 		ApplicationContext ac = new AnnotationConfigApplicationContext(AuditableListener.class);
 
 		AuditablePayloadEvent<String> event = new AuditablePayloadEvent<>(this, "xyz");
@@ -46,7 +77,7 @@ public class PayloadApplicationEventTests {
 	}
 
 	@Test
-	public void testProgrammaticEventListener() {
+	void testProgrammaticEventListener() {
 		List<Auditable> events = new ArrayList<>();
 		ApplicationListener<AuditablePayloadEvent<String>> listener = events::add;
 		ApplicationListener<AuditablePayloadEvent<Integer>> mismatch = (event -> event.getPayload().intValue());
@@ -62,7 +93,7 @@ public class PayloadApplicationEventTests {
 	}
 
 	@Test
-	public void testProgrammaticPayloadListener() {
+	void testProgrammaticPayloadListener() {
 		List<String> events = new ArrayList<>();
 		ApplicationListener<PayloadApplicationEvent<String>> listener = ApplicationListener.forPayload(events::add);
 		ApplicationListener<PayloadApplicationEvent<Integer>> mismatch = ApplicationListener.forPayload(payload -> payload.intValue());
@@ -102,4 +133,14 @@ public class PayloadApplicationEventTests {
 		}
 	}
 
+	static class NumberHolder<T extends Number> {
+
+		private T number;
+
+		public NumberHolder(T number) {
+			this.number = number;
+		}
+
+	}
+
 }