ApplicationListener detection for inner beans behind post-processors

Issue: SPR-14783

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -47,6 +47,7 @@ import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.EmbeddedValueResolverAware;
 import org.springframework.context.EnvironmentAware;
 import org.springframework.context.HierarchicalMessageSource;
 import org.springframework.context.LifecycleProcessor;
@@ -630,11 +631,12 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 
 		// Configure the bean factory with context callbacks.
 		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
+		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
+		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
 		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
 		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
 		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
 		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
-		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
 
 		// BeanFactory interface not registered as resolvable type in a plain factory.
 		// MessageSource registered (and found for autowiring) as a bean.
@@ -643,6 +645,9 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
 		beanFactory.registerResolvableDependency(ApplicationContext.class, this);
 
+		// Register early post-processor for detecting inner beans as ApplicationListeners.
+		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
+
 		// Detect a LoadTimeWeaver and prepare for weaving, if found.
 		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
 			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));

spring-context/src/main/java/org/springframework/context/support/ApplicationListenerDetector.java

@@ -0,0 +1,119 @@
+/*
+ * 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://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.support;
+
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
+import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
+import org.springframework.beans.factory.support.RootBeanDefinition;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.event.ApplicationEventMulticaster;
+
+/**
+ * {@code BeanPostProcessor} that detects beans which implement the {@code ApplicationListener}
+ * interface. This catches beans that can't reliably be detected by {@code getBeanNamesForType}
+ * and related operations which only work against top-level beans.
+ *
+ * <p>With standard Java serialization, this post-processor won't get serialized as part of
+ * {@code DisposableBeanAdapter} to begin with. However, with alternative serialization
+ * mechanisms, {@code DisposableBeanAdapter.writeReplace} might not get used at all, so we
+ * defensively mark this post-processor's field state as {@code transient}.
+ *
+ * @author Juergen Hoeller
+ * @since 4.3.4
+ */
+class ApplicationListenerDetector implements DestructionAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor {
+
+	private static final Log logger = LogFactory.getLog(ApplicationListenerDetector.class);
+
+	private transient final AbstractApplicationContext applicationContext;
+
+	private transient final Map<String, Boolean> singletonNames = new ConcurrentHashMap<>(256);
+
+
+	public ApplicationListenerDetector(AbstractApplicationContext applicationContext) {
+		this.applicationContext = applicationContext;
+	}
+
+
+	@Override
+	public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
+		if (this.applicationContext != null && beanDefinition.isSingleton()) {
+			this.singletonNames.put(beanName, Boolean.TRUE);
+		}
+	}
+
+	@Override
+	public Object postProcessBeforeInitialization(Object bean, String beanName) {
+		return bean;
+	}
+
+	@Override
+	public Object postProcessAfterInitialization(Object bean, String beanName) {
+		if (this.applicationContext != null && bean instanceof ApplicationListener) {
+			// potentially not detected as a listener by getBeanNamesForType retrieval
+			Boolean flag = this.singletonNames.get(beanName);
+			if (Boolean.TRUE.equals(flag)) {
+				// singleton bean (top-level or inner): register on the fly
+				this.applicationContext.addApplicationListener((ApplicationListener<?>) bean);
+			}
+			else if (flag == null) {
+				if (logger.isWarnEnabled() && !this.applicationContext.containsBean(beanName)) {
+					// inner bean with other scope - can't reliably process events
+					logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
+							"but is not reachable for event multicasting by its containing ApplicationContext " +
+							"because it does not have singleton scope. Only top-level listener beans are allowed " +
+							"to be of non-singleton scope.");
+				}
+				this.singletonNames.put(beanName, Boolean.FALSE);
+			}
+		}
+		return bean;
+	}
+
+	@Override
+	public void postProcessBeforeDestruction(Object bean, String beanName) {
+		if (bean instanceof ApplicationListener) {
+			ApplicationEventMulticaster multicaster = this.applicationContext.getApplicationEventMulticaster();
+			multicaster.removeApplicationListener((ApplicationListener<?>) bean);
+			multicaster.removeApplicationListenerBean(beanName);
+		}
+	}
+
+	@Override
+	public boolean requiresDestruction(Object bean) {
+		return (bean instanceof ApplicationListener);
+	}
+
+
+	@Override
+	public boolean equals(Object other) {
+		return (this == other || (other instanceof ApplicationListenerDetector &&
+				this.applicationContext == ((ApplicationListenerDetector) other).applicationContext));
+	}
+
+	@Override
+	public int hashCode() {
+		return this.applicationContext.hashCode();
+	}
+
+}

spring-context/src/main/java/org/springframework/context/support/PostProcessorRegistrationDelegate.java

@@ -23,9 +23,7 @@ import java.util.Comparator;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -34,14 +32,11 @@ import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
-import org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.MergedBeanDefinitionPostProcessor;
 import org.springframework.beans.factory.support.RootBeanDefinition;
-import org.springframework.context.ApplicationListener;
-import org.springframework.context.event.ApplicationEventMulticaster;
 import org.springframework.core.OrderComparator;
 import org.springframework.core.Ordered;
 import org.springframework.core.PriorityOrdered;
@@ -249,6 +244,8 @@ class PostProcessorRegistrationDelegate {
 		sortPostProcessors(beanFactory, internalPostProcessors);
 		registerBeanPostProcessors(beanFactory, internalPostProcessors);
 
+		// Re-register post-processor for detecting inner beans as ApplicationListeners,
+		// moving it to the end of the processor chain (for picking up proxies etc).
 		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
 	}
 
@@ -342,78 +339,4 @@ class PostProcessorRegistrationDelegate {
 		}
 	}
 
-
-	/**
-	 * {@code BeanPostProcessor} that detects beans which implement the {@code ApplicationListener}
-	 * interface. This catches beans that can't reliably be detected by {@code getBeanNamesForType}
-	 * and related operations which only work against top-level beans.
-	 *
-	 * <p>With standard Java serialization, this post-processor won't get serialized as part of
-	 * {@code DisposableBeanAdapter} to begin with. However, with alternative serialization
-	 * mechanisms, {@code DisposableBeanAdapter.writeReplace} might not get used at all, so we
-	 * defensively mark this post-processor's field state as {@code transient}.
-	 */
-	private static class ApplicationListenerDetector
-			implements DestructionAwareBeanPostProcessor, MergedBeanDefinitionPostProcessor {
-
-		private static final Log logger = LogFactory.getLog(ApplicationListenerDetector.class);
-
-		private transient final AbstractApplicationContext applicationContext;
-
-		private transient final Map<String, Boolean> singletonNames = new ConcurrentHashMap<>(256);
-
-		public ApplicationListenerDetector(AbstractApplicationContext applicationContext) {
-			this.applicationContext = applicationContext;
-		}
-
-		@Override
-		public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
-			if (this.applicationContext != null && beanDefinition.isSingleton()) {
-				this.singletonNames.put(beanName, Boolean.TRUE);
-			}
-		}
-
-		@Override
-		public Object postProcessBeforeInitialization(Object bean, String beanName) {
-			return bean;
-		}
-
-		@Override
-		public Object postProcessAfterInitialization(Object bean, String beanName) {
-			if (this.applicationContext != null && bean instanceof ApplicationListener) {
-				// potentially not detected as a listener by getBeanNamesForType retrieval
-				Boolean flag = this.singletonNames.get(beanName);
-				if (Boolean.TRUE.equals(flag)) {
-					// singleton bean (top-level or inner): register on the fly
-					this.applicationContext.addApplicationListener((ApplicationListener<?>) bean);
-				}
-				else if (flag == null) {
-					if (logger.isWarnEnabled() && !this.applicationContext.containsBean(beanName)) {
-						// inner bean with other scope - can't reliably process events
-						logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
-								"but is not reachable for event multicasting by its containing ApplicationContext " +
-								"because it does not have singleton scope. Only top-level listener beans are allowed " +
-								"to be of non-singleton scope.");
-					}
-					this.singletonNames.put(beanName, Boolean.FALSE);
-				}
-			}
-			return bean;
-		}
-
-		@Override
-		public void postProcessBeforeDestruction(Object bean, String beanName) {
-			if (bean instanceof ApplicationListener) {
-				ApplicationEventMulticaster multicaster = this.applicationContext.getApplicationEventMulticaster();
-				multicaster.removeApplicationListener((ApplicationListener<?>) bean);
-				multicaster.removeApplicationListenerBean(beanName);
-			}
-		}
-
-		@Override
-		public boolean requiresDestruction(Object bean) {
-			return (bean instanceof ApplicationListener);
-		}
-	}
-
 }

spring-context/src/test/java/org/springframework/context/support/BeanFactoryPostProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 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.
@@ -28,8 +28,12 @@ import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProce
 import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationEvent;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.core.PriorityOrdered;
 import org.springframework.tests.sample.beans.TestBean;
+import org.springframework.util.Assert;
 
 import static org.junit.Assert.*;
 
@@ -119,6 +123,24 @@ public class BeanFactoryPostProcessorTests {
 		assertTrue(ac.getBean(TestBeanFactoryPostProcessor.class).wasCalled);
 	}
 
+	@Test
+	public void testBeanFactoryPostProcessorAsApplicationListener() {
+		StaticApplicationContext ac = new StaticApplicationContext();
+		ac.registerBeanDefinition("bfpp", new RootBeanDefinition(ListeningBeanFactoryPostProcessor.class));
+		ac.refresh();
+		assertTrue(ac.getBean(ListeningBeanFactoryPostProcessor.class).received instanceof ContextRefreshedEvent);
+	}
+
+	@Test
+	public void testBeanFactoryPostProcessorWithInnerBeanAsApplicationListener() {
+		StaticApplicationContext ac = new StaticApplicationContext();
+		RootBeanDefinition rbd = new RootBeanDefinition(NestingBeanFactoryPostProcessor.class);
+		rbd.getPropertyValues().add("listeningBean", new RootBeanDefinition(ListeningBean.class));
+		ac.registerBeanDefinition("bfpp", rbd);
+		ac.refresh();
+		assertTrue(ac.getBean(NestingBeanFactoryPostProcessor.class).getListeningBean().received instanceof ContextRefreshedEvent);
+	}
+
 
 	public static class TestBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
 
@@ -170,4 +192,50 @@ public class BeanFactoryPostProcessorTests {
 		}
 	}
 
+
+	public static class ListeningBeanFactoryPostProcessor implements BeanFactoryPostProcessor, ApplicationListener {
+
+		public ApplicationEvent received;
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+		}
+
+		@Override
+		public void onApplicationEvent(ApplicationEvent event) {
+			Assert.state(this.received == null, "Just one ContextRefreshedEvent expected");
+			this.received = event;
+		}
+	}
+
+
+	public static class ListeningBean implements ApplicationListener {
+
+		public ApplicationEvent received;
+
+		@Override
+		public void onApplicationEvent(ApplicationEvent event) {
+			Assert.state(this.received == null, "Just one ContextRefreshedEvent expected");
+			this.received = event;
+		}
+	}
+
+
+	public static class NestingBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
+
+		private ListeningBean listeningBean;
+
+		public void setListeningBean(ListeningBean listeningBean) {
+			this.listeningBean = listeningBean;
+		}
+
+		public ListeningBean getListeningBean() {
+			return listeningBean;
+		}
+
+		@Override
+		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+		}
+	}
+
 }