Consistent lazy resolution of default executor/scheduler for Async/ScheduledAnnotationBeanPostProcessor

Issue: SPR-14030

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -42,7 +42,8 @@ public class AnnotationAsyncExecutionInterceptor extends AsyncExecutionIntercept
 	 * Create a new {@code AnnotationAsyncExecutionInterceptor} with the given executor
 	 * and a simple {@link AsyncUncaughtExceptionHandler}.
 	 * @param defaultExecutor the executor to be used by default if no more specific
-	 * executor has been qualified at the method level using {@link Async#value()}
+	 * executor has been qualified at the method level using {@link Async#value()};
+	 * as of 4.2.6, a local executor for this interceptor will be built otherwise
 	 */
 	public AnnotationAsyncExecutionInterceptor(Executor defaultExecutor) {
 		super(defaultExecutor);
@@ -51,7 +52,8 @@ public class AnnotationAsyncExecutionInterceptor extends AsyncExecutionIntercept
 	/**
 	 * Create a new {@code AnnotationAsyncExecutionInterceptor} with the given executor.
 	 * @param defaultExecutor the executor to be used by default if no more specific
-	 * executor has been qualified at the method level using {@link Async#value()}
+	 * executor has been qualified at the method level using {@link Async#value()};
+	 * as of 4.2.6, a local executor for this interceptor will be built otherwise
 	 * @param exceptionHandler the {@link AsyncUncaughtExceptionHandler} to use to
 	 * handle exceptions thrown by asynchronous method executions with {@code void}
 	 * return type
@@ -74,7 +76,7 @@ public class AnnotationAsyncExecutionInterceptor extends AsyncExecutionIntercept
 	 */
 	@Override
 	protected String getExecutorQualifier(Method method) {
-		// maintainer's note: changes made here should also be made in
+		// Maintainer's note: changes made here should also be made in
 		// AnnotationAsyncExecutionAspect#getExecutorQualifier
 		Async async = AnnotationUtils.findAnnotation(method, Async.class);
 		if (async == null) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -32,7 +32,6 @@ import org.springframework.aop.support.ComposablePointcut;
 import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
-import org.springframework.core.task.SimpleAsyncTaskExecutor;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 
@@ -73,8 +72,10 @@ public class AsyncAnnotationAdvisor extends AbstractPointcutAdvisor implements B
 	/**
 	 * Create a new {@code AsyncAnnotationAdvisor} for the given task executor.
 	 * @param executor the task executor to use for asynchronous methods
-	 * @param exceptionHandler the {@link org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler} to use to
+	 * (can be {@code null} to trigger default executor resolution)
+	 * @param exceptionHandler the {@link AsyncUncaughtExceptionHandler} to use to
 	 * handle unexpected exception thrown by asynchronous method executions
+	 * @see AnnotationAsyncExecutionInterceptor#getDefaultExecutor(BeanFactory)
 	 */
 	@SuppressWarnings("unchecked")
 	public AsyncAnnotationAdvisor(Executor executor, AsyncUncaughtExceptionHandler exceptionHandler) {
@@ -87,9 +88,6 @@ public class AsyncAnnotationAdvisor extends AbstractPointcutAdvisor implements B
 		catch (ClassNotFoundException ex) {
 			// If EJB 3.1 API not present, simply ignore.
 		}
-		if (executor == null) {
-			executor = new SimpleAsyncTaskExecutor();
-		}
 		if (exceptionHandler != null) {
 			this.exceptionHandler = exceptionHandler;
 		}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -25,8 +25,6 @@ import org.apache.commons.logging.LogFactory;
 import org.springframework.aop.framework.autoproxy.AbstractBeanFactoryAwareAdvisingPostProcessor;
 import org.springframework.aop.interceptor.AsyncUncaughtExceptionHandler;
 import org.springframework.beans.factory.BeanFactory;
-import org.springframework.beans.factory.NoSuchBeanDefinitionException;
-import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.core.task.TaskExecutor;
 import org.springframework.util.Assert;
 
@@ -68,8 +66,10 @@ public class AsyncAnnotationBeanPostProcessor extends AbstractBeanFactoryAwareAd
 	 * <p>Note that the initial lookup happens by type; this is just the fallback
 	 * in case of multiple executor beans found in the context.
 	 * @since 4.2
+	 * @see AnnotationAsyncExecutionInterceptor#DEFAULT_TASK_EXECUTOR_BEAN_NAME
 	 */
-	public static final String DEFAULT_TASK_EXECUTOR_BEAN_NAME = "taskExecutor";
+	public static final String DEFAULT_TASK_EXECUTOR_BEAN_NAME =
+			AnnotationAsyncExecutionInterceptor.DEFAULT_TASK_EXECUTOR_BEAN_NAME;
 
 
 	protected final Log logger = LogFactory.getLog(getClass());
@@ -102,6 +102,13 @@ public class AsyncAnnotationBeanPostProcessor extends AbstractBeanFactoryAwareAd
 
 	/**
 	 * Set the {@link Executor} to use when invoking methods asynchronously.
+	 * <p>If not specified, default executor resolution will apply: searching for a
+	 * unique {@link TaskExecutor} bean in the context, or for an {@link Executor}
+	 * bean named "taskExecutor" otherwise. If neither of the two is resolvable,
+	 * a local default executor will be created within the interceptor.
+	 * @see AsyncAnnotationAdvisor#AsyncAnnotationAdvisor(Executor, AsyncUncaughtExceptionHandler)
+	 * @see AnnotationAsyncExecutionInterceptor#getDefaultExecutor(BeanFactory)
+	 * @see #DEFAULT_TASK_EXECUTOR_BEAN_NAME
 	 */
 	public void setExecutor(Executor executor) {
 		this.executor = executor;
@@ -121,31 +128,7 @@ public class AsyncAnnotationBeanPostProcessor extends AbstractBeanFactoryAwareAd
 	public void setBeanFactory(BeanFactory beanFactory) {
 		super.setBeanFactory(beanFactory);
 
-		Executor executorToUse = this.executor;
-		if (executorToUse == null) {
-			try {
-				// Search for TaskExecutor bean... not plain Executor since that would
-				// match with ScheduledExecutorService as well, which is unusable for
-				// our purposes here. TaskExecutor is more clearly designed for it.
-				executorToUse = beanFactory.getBean(TaskExecutor.class);
-			}
-			catch (NoUniqueBeanDefinitionException ex) {
-				try {
-					executorToUse = beanFactory.getBean(DEFAULT_TASK_EXECUTOR_BEAN_NAME, Executor.class);
-				}
-				catch (NoSuchBeanDefinitionException ex2) {
-					logger.info("More than one TaskExecutor bean found within the context, and none is " +
-							"named 'taskExecutor'. Mark one of them as primary or name it 'taskExecutor' " +
-							"(possibly as an alias) in order to use it for async annotation processing.");
-				}
-			}
-			catch (NoSuchBeanDefinitionException ex) {
-				logger.info("No TaskExecutor bean found for async annotation processing.");
-				// Giving up -> falling back to default executor within the advisor...
-			}
-		}
-
-		AsyncAnnotationAdvisor advisor =  new AsyncAnnotationAdvisor(executorToUse, this.exceptionHandler);
+		AsyncAnnotationAdvisor advisor = new AsyncAnnotationAdvisor(this.executor, this.exceptionHandler);
 		if (this.asyncAnnotationType != null) {
 			advisor.setAsyncAnnotationType(this.asyncAnnotationType);
 		}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -41,26 +41,28 @@ import org.springframework.core.Ordered;
  * @Configuration
  * @EnableAsync
  * public class AppConfig {
+ *
  *     @Bean
  *     public MyAsyncBean asyncBean() {
  *         return new MyAsyncBean();
  *     }
  * }</pre>
  *
- *
  * <p>The {@link #mode} attribute controls how advice is applied; if the mode is
  * {@link AdviceMode#PROXY} (the default), then the other attributes control the behavior
  * of the proxying.
  *
- * <p>Note that if the {@linkplain #mode} is set to {@link AdviceMode#ASPECTJ}, then
- * the value of the {@link #proxyTargetClass} attribute will be ignored. Note also
- * that in this case the {@code spring-aspects} module JAR must be present on the
- * classpath.
+ * <p>Note that if the {@linkplain #mode} is set to {@link AdviceMode#ASPECTJ}, then the
+ * value of the {@link #proxyTargetClass} attribute will be ignored. Note also that in
+ * this case the {@code spring-aspects} module JAR must be present on the classpath.
  *
- * <p>By default, a {@link org.springframework.core.task.SimpleAsyncTaskExecutor
- * SimpleAsyncTaskExecutor} will be used to process async method invocations. Besides,
- * annotated methods having a {@code void} return type cannot transmit any exception
- * back to the caller. By default, such uncaught exceptions are only logged.
+ * <p>By default, Spring will be searching for an associated thread pool definition:
+ * either a unique {@link org.springframework.core.task.TaskExecutor} bean in the context,
+ * or an {@link java.util.concurrent.Executor} bean named "taskExecutor" otherwise. If
+ * neither of the two is resolvable, a {@link org.springframework.core.task.SimpleAsyncTaskExecutor}
+ * will be used to process async method invocations. Besides, annotated methods having a
+ * {@code void} return type cannot transmit any exception back to the caller. By default,
+ * such uncaught exceptions are only logged.
  *
  * <p>To customize all this, implement {@link AsyncConfigurer} and
  * provide:
@@ -129,6 +131,7 @@ import org.springframework.core.Ordered;
  * through direct access to actual componentry.
  *
  * @author Chris Beams
+ * @author Juergen Hoeller
  * @author Stephane Nicoll
  * @author Sam Brannen
  * @since 3.1
@@ -175,9 +178,8 @@ public @interface EnableAsync {
 	AdviceMode mode() default AdviceMode.PROXY;
 
 	/**
-	 * Indicate the order in which the
-	 * {@link org.springframework.scheduling.annotation.AsyncAnnotationBeanPostProcessor
-	 * AsyncAnnotationBeanPostProcessor} should be applied.
+	 * Indicate the order in which the {@link AsyncAnnotationBeanPostProcessor}
+	 * should be applied.
 	 * <p>The default is {@link Ordered#LOWEST_PRECEDENCE} in order to run
 	 * after all other post-processors, so that it can add an advisor to
 	 * existing proxies rather than double-proxy.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -37,16 +37,18 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * @Configuration
  * @EnableScheduling
  * public class AppConfig {
+ *
  *     // various @Bean definitions
  * }</pre>
  *
  * This enables detection of @{@link Scheduled} annotations on any Spring-managed
- * bean in the container.  For example, given a class {@code MyTask}
+ * bean in the container. For example, given a class {@code MyTask}
  *
  * <pre class="code">
  * package com.myco.tasks;
  *
  * public class MyTask {
+ *
  *     &#064;Scheduled(fixedRate=1000)
  *     public void work() {
  *         // task execution logic
@@ -60,6 +62,7 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * &#064;Configuration
  * &#064;EnableScheduling
  * public class AppConfig {
+ *
  *     &#064;Bean
  *     public MyTask task() {
  *         return new MyTask();
@@ -84,14 +87,21 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * &#064;Configuration
  * &#064;EnableScheduling
  * public class AppConfig {
+ *
  *     &#064;Scheduled(fixedRate=1000)
  *     public void work() {
  *         // task execution logic
  *     }
  * }</pre>
  *
- * In all of the above scenarios, a default single-threaded task executor is used.
- * When more control is desired, a {@code @Configuration} class may implement
+ * <p>By default, will be searching for an associated scheduler definition: either
+ * a unique {@link org.springframework.scheduling.TaskScheduler} bean in the context,
+ * or a {@code TaskScheduler} bean named "taskScheduler" otherwise; the same lookup
+ * will also be performed for a {@link java.util.concurrent.ScheduledExecutorService}
+ * bean. If neither of the two is resolvable, a local single-threaded default
+ * scheduler will be created and used within the registrar.
+ *
+ * <p>When more control is desired, a {@code @Configuration} class may implement
  * {@link SchedulingConfigurer}. This allows access to the underlying
  * {@link ScheduledTaskRegistrar} instance. For example, the following example
  * demonstrates how to customize the {@link Executor} used to execute scheduled
@@ -101,6 +111,7 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * &#064;Configuration
  * &#064;EnableScheduling
  * public class AppConfig implements SchedulingConfigurer {
+ *
  *     &#064;Override
  *     public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
  *         taskRegistrar.setScheduler(taskExecutor());
@@ -112,11 +123,11 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  *     }
  * }</pre>
  *
- * Note in the example above the use of {@code @Bean(destroyMethod="shutdown")}. This
- * ensures that the task executor is properly shut down when the Spring application
- * context itself is closed.
+ * <p>Note in the example above the use of {@code @Bean(destroyMethod="shutdown")}.
+ * This ensures that the task executor is properly shut down when the Spring
+ * application context itself is closed.
  *
- * Implementing {@code SchedulingConfigurer} also allows for fine-grained
+ * <p>Implementing {@code SchedulingConfigurer} also allows for fine-grained
  * control over task registration via the {@code ScheduledTaskRegistrar}.
  * For example, the following configures the execution of a particular bean
  * method per a custom {@code Trigger} implementation:
@@ -125,6 +136,7 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * &#064;Configuration
  * &#064;EnableScheduling
  * public class AppConfig implements SchedulingConfigurer {
+ *
  *     &#064;Override
  *     public void configureTasks(ScheduledTaskRegistrar taskRegistrar) {
  *         taskRegistrar.setScheduler(taskScheduler());
@@ -167,6 +179,7 @@ import org.springframework.scheduling.config.ScheduledTaskRegistrar;
  * through direct access to actual componentry.<p>
  *
  * @author Chris Beams
+ * @author Juergen Hoeller
  * @since 3.1
  * @see Scheduled
  * @see SchedulingConfiguration

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -89,6 +89,7 @@ public class ScheduledAnnotationBeanPostProcessor implements BeanPostProcessor,
 	 * The default name of the {@link TaskScheduler} bean to pick up: "taskScheduler".
 	 * <p>Note that the initial lookup happens by type; this is just the fallback
 	 * in case of multiple scheduler beans found in the context.
+	 * @since 4.2
 	 */
 	public static final String DEFAULT_TASK_SCHEDULER_BEAN_NAME = "taskScheduler";
 
@@ -118,6 +119,12 @@ public class ScheduledAnnotationBeanPostProcessor implements BeanPostProcessor,
 	 * Set the {@link org.springframework.scheduling.TaskScheduler} that will invoke
 	 * the scheduled methods, or a {@link java.util.concurrent.ScheduledExecutorService}
 	 * to be wrapped as a TaskScheduler.
+	 * <p>If not specified, default scheduler resolution will apply: searching for a
+	 * unique {@link TaskScheduler} bean in the context, or for a {@link TaskScheduler}
+	 * bean named "taskScheduler" otherwise; the same lookup will also be performed for
+	 * a {@link ScheduledExecutorService} bean. If neither of the two is resolvable,
+	 * a local single-threaded default scheduler will be created within the registrar.
+	 * @see #DEFAULT_TASK_SCHEDULER_BEAN_NAME
 	 */
 	public void setScheduler(Object scheduler) {
 		this.scheduler = scheduler;
@@ -195,10 +202,13 @@ public class ScheduledAnnotationBeanPostProcessor implements BeanPostProcessor,
 							this.beanFactory.getBean(DEFAULT_TASK_SCHEDULER_BEAN_NAME, TaskScheduler.class));
 				}
 				catch (NoSuchBeanDefinitionException ex2) {
-					throw new IllegalStateException("More than one TaskScheduler bean exists within the context, and " +
-							"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' "+
-							"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +
-							"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback.", ex);
+					if (logger.isInfoEnabled()) {
+						logger.info("More than one TaskScheduler bean exists within the context, and " +
+								"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +
+								"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +
+								"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +
+								ex.getBeanNamesFound());
+					}
 				}
 			}
 			catch (NoSuchBeanDefinitionException ex) {
@@ -208,14 +218,24 @@ public class ScheduledAnnotationBeanPostProcessor implements BeanPostProcessor,
 					this.registrar.setScheduler(this.beanFactory.getBean(ScheduledExecutorService.class));
 				}
 				catch (NoUniqueBeanDefinitionException ex2) {
-					throw new IllegalStateException("More than one ScheduledExecutorService bean exists within " +
-							"the context. Mark one of them as primary; or implement the SchedulingConfigurer " +
-							"interface and call ScheduledTaskRegistrar#setScheduler explicitly within the " +
-							"configureTasks() callback.", ex);
+					try {
+						this.registrar.setScheduler(
+								this.beanFactory.getBean(DEFAULT_TASK_SCHEDULER_BEAN_NAME, ScheduledExecutorService.class));
+					}
+					catch (NoSuchBeanDefinitionException ex3) {
+						if (logger.isInfoEnabled()) {
+							logger.info("More than one ScheduledExecutorService bean exists within the context, and " +
+									"none is named 'taskScheduler'. Mark one of them as primary or name it 'taskScheduler' " +
+									"(possibly as an alias); or implement the SchedulingConfigurer interface and call " +
+									"ScheduledTaskRegistrar#setScheduler explicitly within the configureTasks() callback: " +
+									ex2.getBeanNamesFound());
+						}
+					}
 				}
 				catch (NoSuchBeanDefinitionException ex2) {
-					logger.debug("Could not find default ScheduledExecutorService bean", ex);
+					logger.debug("Could not find default ScheduledExecutorService bean", ex2);
 					// Giving up -> falling back to default scheduler within the registrar...
+					logger.info("No TaskScheduler/ScheduledExecutorService bean found for scheduled processing");
 				}
 			}
 		}