Consistently accept "taskExecutor" bean of type Executor (as stated in @EnableAsync's javadoc)

Issue: SPR-15566
(cherry picked from commit 3cc94ae)

Author: jhoeller

spring-aop/src/main/java/org/springframework/aop/interceptor/AsyncExecutionAspectSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -228,6 +228,7 @@ protected Executor getDefaultExecutor(BeanFactory beanFactory) {
 				return beanFactory.getBean(TaskExecutor.class);
 			}
 			catch (NoUniqueBeanDefinitionException ex) {
+				logger.debug("Could not find unique TaskExecutor bean", ex);
 				try {
 					return beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, Executor.class);
 				}
@@ -241,8 +242,14 @@ protected Executor getDefaultExecutor(BeanFactory beanFactory) {
 			}
 			catch (NoSuchBeanDefinitionException ex) {
 				logger.debug("Could not find default TaskExecutor bean", ex);
+				try {
+					return beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, Executor.class);
+				}
+				catch (NoSuchBeanDefinitionException ex2) {
+					logger.info("No task executor bean found for async processing: " +
+							"no bean of type TaskExecutor and no bean named 'taskExecutor' either");
+				}
 				// Giving up -> either using local default executor or none at all...
-				logger.info("No TaskExecutor bean found for async processing");
 			}
 		}
 		return null;

spring-context/src/main/java/org/springframework/scheduling/annotation/ScheduledAnnotationBeanPostProcessor.java

@@ -221,6 +221,7 @@ private void finishRegistration() {
 				this.registrar.setTaskScheduler(resolveSchedulerBean(TaskScheduler.class, false));
 			}
 			catch (NoUniqueBeanDefinitionException ex) {
+				logger.debug("Could not find unique TaskScheduler bean", ex);
 				try {
 					this.registrar.setTaskScheduler(resolveSchedulerBean(TaskScheduler.class, true));
 				}
@@ -241,6 +242,7 @@ private void finishRegistration() {
 					this.registrar.setScheduler(resolveSchedulerBean(ScheduledExecutorService.class, false));
 				}
 				catch (NoUniqueBeanDefinitionException ex2) {
+					logger.debug("Could not find unique ScheduledExecutorService bean", ex2);
 					try {
 						this.registrar.setScheduler(resolveSchedulerBean(ScheduledExecutorService.class, true));
 					}

spring-context/src/test/java/org/springframework/scheduling/annotation/EnableAsyncTests.java

@@ -23,6 +23,7 @@
 import java.lang.reflect.Method;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 
 import org.junit.Ignore;
@@ -43,6 +44,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Lazy;
 import org.springframework.core.Ordered;
+import org.springframework.scheduling.concurrent.CustomizableThreadFactory;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;
 import org.springframework.stereotype.Component;
 import org.springframework.util.ReflectionUtils;
@@ -181,9 +183,23 @@ public void aspectModeAspectJAttemptsToRegisterAsyncAspect() {
 	}
 
 	@Test
-	public void customExecutorIsPropagated() throws InterruptedException {
+	public void customExecutorBean() throws InterruptedException {
 		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
-		ctx.register(CustomExecutorAsyncConfig.class);
+		ctx.register(CustomExecutorBean.class);
+		ctx.refresh();
+
+		AsyncBean asyncBean = ctx.getBean(AsyncBean.class);
+		asyncBean.work();
+		Thread.sleep(500);
+		assertThat(asyncBean.getThreadOfExecution().getName(), startsWith("Custom-"));
+
+		ctx.close();
+	}
+
+	@Test
+	public void customExecutorConfig() throws InterruptedException {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(CustomExecutorConfig.class);
 		ctx.refresh();
 
 		AsyncBean asyncBean = ctx.getBean(AsyncBean.class);
@@ -382,7 +398,23 @@ public Executor otherExecutor() {
 
 	@Configuration
 	@EnableAsync
-	static class CustomExecutorAsyncConfig implements AsyncConfigurer {
+	static class CustomExecutorBean {
+
+		@Bean
+		public AsyncBean asyncBean() {
+			return new AsyncBean();
+		}
+
+		@Bean
+		public Executor taskExecutor() {
+			return Executors.newSingleThreadExecutor(new CustomizableThreadFactory("Custom-"));
+		}
+	}
+
+
+	@Configuration
+	@EnableAsync
+	static class CustomExecutorConfig implements AsyncConfigurer {
 
 		@Bean
 		public AsyncBean asyncBean() {