Retrofit events for generics matching of ApplicationEvent subtypes with generic payload parameter.

Closes #1539

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/event/RelationalEvent.java

@@ -15,6 +15,8 @@
  */
 package org.springframework.data.relational.core.mapping.event;
 
+import org.springframework.core.ResolvableType;
+import org.springframework.core.ResolvableTypeProvider;
 import org.springframework.lang.Nullable;
 
 /**
@@ -25,7 +27,7 @@ import org.springframework.lang.Nullable;
  * @author Mark Paluch
  * @author Jens Schauder
  */
-public interface RelationalEvent<E> {
+public interface RelationalEvent<E> extends ResolvableTypeProvider {
 
 	/**
 	 * @return the entity to which this event refers. Might be {@literal null}.
@@ -38,4 +40,9 @@ public interface RelationalEvent<E> {
 	 * @since 2.0
 	 */
 	Class<E> getType();
+
+	@Override
+	default ResolvableType getResolvableType() {
+		return ResolvableType.forClassWithGenerics(getClass(), getType());
+	}
 }

spring-data-relational/src/test/java/org/springframework/data/relational/core/mapping/event/RelationalEventUnitTests.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2023 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.relational.core.mapping.event;
+
+import static org.assertj.core.api.AssertionsForClassTypes.*;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.core.ResolvableType;
+
+/**
+ * Unit tests for {@link RelationalEvent}.
+ *
+ * @author Mark Paluch
+ */
+class RelationalEventUnitTests {
+
+	@Test // GH-1539
+	void shouldReportCorrectGenericType() {
+		assertThat(new BeforeConvertEvent<>(new MyAggregate()).getResolvableType())
+				.isEqualTo(ResolvableType.forClassWithGenerics(BeforeConvertEvent.class, MyAggregate.class));
+	}
+
+	static class MyAggregate {}
+}