From 22db1ac14635eb6599eff1708f02a4f7a2cb63eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Deleuze?= <sdeleuze@vmware.com>
Date: Tue, 17 Oct 2023 12:09:48 +0200
Subject: [PATCH] Add Coroutines support for `@EventListener`

Closes gh-28343
---
 .../ApplicationListenerMethodAdapter.java     |  8 +-
 ...inApplicationListenerMethodAdapterTests.kt | 83 +++++++++++++++++++
 2 files changed, 90 insertions(+), 1 deletion(-)
 create mode 100644 spring-context/src/test/kotlin/org/springframework/context/event/KotlinApplicationListenerMethodAdapterTests.kt

diff --git a/spring-context/src/main/java/org/springframework/context/event/ApplicationListenerMethodAdapter.java b/spring-context/src/main/java/org/springframework/context/event/ApplicationListenerMethodAdapter.java
index 9790d7070c8..b80bd9a19db 100644
--- a/spring-context/src/main/java/org/springframework/context/event/ApplicationListenerMethodAdapter.java
+++ b/spring-context/src/main/java/org/springframework/context/event/ApplicationListenerMethodAdapter.java
@@ -38,6 +38,8 @@ import org.springframework.context.ApplicationEvent;
 import org.springframework.context.PayloadApplicationEvent;
 import org.springframework.context.expression.AnnotatedElementKey;
 import org.springframework.core.BridgeMethodResolver;
+import org.springframework.core.CoroutinesUtils;
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.Ordered;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
@@ -64,6 +66,7 @@ import org.springframework.util.StringUtils;
  * @author Stephane Nicoll
  * @author Juergen Hoeller
  * @author Sam Brannen
+ * @author Sebastien Deleuze
  * @since 4.2
  */
 public class ApplicationListenerMethodAdapter implements GenericApplicationListener {
@@ -121,7 +124,7 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 	}
 
 	private static List<ResolvableType> resolveDeclaredEventTypes(Method method, @Nullable EventListener ann) {
-		int count = method.getParameterCount();
+		int count = (KotlinDetector.isSuspendingFunction(method) ? method.getParameterCount() - 1 : method.getParameterCount());
 		if (count > 1) {
 			throw new IllegalStateException(
 					"Maximum one parameter is allowed for event listener method: " + method);
@@ -356,6 +359,9 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 
 		ReflectionUtils.makeAccessible(this.method);
 		try {
+			if (KotlinDetector.isSuspendingFunction(this.method)) {
+				return CoroutinesUtils.invokeSuspendingFunction(this.method, bean, args);
+			}
 			return this.method.invoke(bean, args);
 		}
 		catch (IllegalArgumentException ex) {
diff --git a/spring-context/src/test/kotlin/org/springframework/context/event/KotlinApplicationListenerMethodAdapterTests.kt b/spring-context/src/test/kotlin/org/springframework/context/event/KotlinApplicationListenerMethodAdapterTests.kt
new file mode 100644
index 00000000000..6141b354d51
--- /dev/null
+++ b/spring-context/src/test/kotlin/org/springframework/context/event/KotlinApplicationListenerMethodAdapterTests.kt
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2002-2023 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.context.event
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+import org.mockito.Mockito
+import org.springframework.context.ApplicationEvent
+import org.springframework.core.ResolvableType
+import org.springframework.util.ReflectionUtils
+import java.lang.reflect.Method
+import kotlin.coroutines.Continuation
+
+/**
+ * Kotlin tests for [ApplicationListenerMethodAdapter].
+ *
+ * @author Sebastien Deleuze
+ */
+class KotlinApplicationListenerMethodAdapterTests {
+
+	private val sampleEvents = Mockito.spy(SampleEvents())
+
+	@Test
+	fun rawListener() {
+		val method = ReflectionUtils.findMethod(SampleEvents::class.java, "handleRaw", ApplicationEvent::class.java, Continuation::class.java)!!
+		supportsEventType(true, method, ResolvableType.forClass(ApplicationEvent::class.java))
+	}
+
+	@Test
+	fun listenerWithMoreThanOneParameter() {
+		val method = ReflectionUtils.findMethod(SampleEvents::class.java, "moreThanOneParameter",
+			String::class.java, Int::class.java, Continuation::class.java)!!
+		Assertions.assertThatIllegalStateException().isThrownBy {
+			createTestInstance(
+				method
+			)
+		}
+	}
+
+	private fun supportsEventType(match: Boolean, method: Method, eventType: ResolvableType) {
+		val adapter: ApplicationListenerMethodAdapter = createTestInstance(method)
+		Assertions.assertThat(adapter.supportsEventType(eventType))
+			.`as`("Wrong match for event '$eventType' on $method").isEqualTo(match)
+	}
+
+	private fun createTestInstance(method: Method): ApplicationListenerMethodAdapter {
+		return StaticApplicationListenerMethodAdapter(method, this.sampleEvents)
+	}
+
+
+	private class StaticApplicationListenerMethodAdapter(method: Method, private val targetBean: Any) :
+		ApplicationListenerMethodAdapter("unused", targetBean.javaClass, method) {
+			public override fun getTargetBean(): Any {
+			return targetBean
+		}
+	}
+
+	@Suppress("RedundantSuspendModifier", "UNUSED_PARAMETER")
+	private class SampleEvents {
+
+		@EventListener
+		suspend fun handleRaw(event: ApplicationEvent) {
+		}
+
+		@EventListener
+		suspend fun moreThanOneParameter(foo: String, bar: Int) {
+		}
+	}
+
+}