INT-2434-v3 polished based on @garyrussell last comments

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractConsumerEndpointParser.java

@@ -16,13 +16,13 @@
 
 package org.springframework.integration.config.xml;
 
-import java.util.HashSet;
+import java.util.Collection;
 import java.util.List;
-import java.util.Set;
 
 import org.w3c.dom.Element;
 
 import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.ConstructorArgumentValues;
 import org.springframework.beans.factory.parsing.BeanComponentDefinition;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
@@ -93,14 +93,12 @@ protected final AbstractBeanDefinition parseInternal(Element element, ParserCont
 
 		if (!parserContext.getRegistry().containsBeanDefinition(inputChannelName)){
 			BeanDefinition channelRegistry = parserContext.getRegistry().getBeanDefinition(ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
-
-			@SuppressWarnings("unchecked")
-			Set<String> channelNames = (Set<String>) channelRegistry.getAttribute(ChannelInitializer.CHANNEL_NAMES_ATTR);
-			if (channelNames == null){
-				channelNames = (Set<String>) new HashSet<String>();
-				channelRegistry.setAttribute(ChannelInitializer.CHANNEL_NAMES_ATTR, channelNames);
+			ConstructorArgumentValues caValues = channelRegistry.getConstructorArgumentValues();
+			if (caValues != null){
+				@SuppressWarnings("unchecked")
+				Collection<String> channelCandidateNames = (Collection<String>) caValues.getArgumentValue(0, Collection.class).getValue();
+				channelCandidateNames.add(inputChannelName);
 			}
-			channelNames.add(inputChannelName);
 		}
 
 		builder.addPropertyValue("inputChannelName", inputChannelName);

spring-integration-core/src/main/java/org/springframework/integration/config/xml/AbstractIntegrationNamespaceHandler.java

@@ -22,9 +22,9 @@
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanDefinitionHolder;
-import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
+import org.springframework.beans.factory.support.ManagedSet;
 import org.springframework.beans.factory.xml.BeanDefinitionDecorator;
 import org.springframework.beans.factory.xml.BeanDefinitionParser;
 import org.springframework.beans.factory.xml.NamespaceHandler;
@@ -68,19 +68,17 @@ public final BeanDefinitionHolder decorate(Node source, BeanDefinitionHolder def
 	}
 
 	/*
-	 * This method will auto-register ChannelInitializer which could also be overridden by the user 
-	 * by simply registering a ChannelInitializer <bean> with 'autoCreate' property set to false.
-	 * It will also register  ChannelInitializer$AutoCreateCandidatesCollector which simply collects channelNames to be created.
-	 * It does a little more so please read its comments. ChannelInitializer$AutoCreateCandidatesCollector 
-	 * can NOT be overridden by the user
+	 * This method will auto-register a ChannelInitializer which could also be overridden by the user 
+	 * by simply registering a ChannelInitializer <bean> with its 'autoCreate' property set to false to suppress channel creation.
+	 * It will also register a ChannelInitializer$AutoCreateCandidatesCollector which simply collects candidate channel names.
 	 */
 	private void registerImplicitChannelCreator(ParserContext parserContext) {
 		// ChannelInitializer
 		boolean alreadyRegistered = false;
-		if (parserContext.getRegistry() instanceof ConfigurableListableBeanFactory) {
+		if (parserContext.getRegistry() instanceof ListableBeanFactory) {
 			// unlike DefaultConfiguringBeanFactoryPostProcessor we need one of these per registry
 			// therefore we need to call containsBeanDefinition(..) which does not consider parent registry
-			alreadyRegistered = ((ConfigurableListableBeanFactory) parserContext.getRegistry()).containsBeanDefinition(CHANNEL_INITIALIZER_BEAN_NAME);
+			alreadyRegistered = ((ListableBeanFactory) parserContext.getRegistry()).containsBeanDefinition(CHANNEL_INITIALIZER_BEAN_NAME);
 		}
 		else {
 			alreadyRegistered = parserContext.getRegistry().isBeanNameInUse(CHANNEL_INITIALIZER_BEAN_NAME);
@@ -92,17 +90,18 @@ private void registerImplicitChannelCreator(ParserContext parserContext) {
 		}
 		// ChannelInitializer$AutoCreateCandidatesCollector
 		alreadyRegistered = false;
-		if (parserContext.getRegistry() instanceof ConfigurableListableBeanFactory) {
+		if (parserContext.getRegistry() instanceof ListableBeanFactory) {
 			// unlike DefaultConfiguringBeanFactoryPostProcessor we need one of these per registry
 			// therefore we need to call containsBeanDefinition(..) which does not consider parent registry
-			alreadyRegistered = ((ConfigurableListableBeanFactory) parserContext.getRegistry()).
+			alreadyRegistered = ((ListableBeanFactory) parserContext.getRegistry()).
 					containsBeanDefinition(ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
 		}
 		else {
 			alreadyRegistered = parserContext.getRegistry().isBeanNameInUse(ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
 		}
 		if (!alreadyRegistered) {
 			BeanDefinitionBuilder channelRegistryBuilder = BeanDefinitionBuilder.genericBeanDefinition(AutoCreateCandidatesCollector.class);
+			channelRegistryBuilder.addConstructorArgValue(new ManagedSet<String>());
 			BeanDefinitionHolder channelRegistryHolder = 
 					new BeanDefinitionHolder(channelRegistryBuilder.getBeanDefinition(), ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
 			BeanDefinitionReaderUtils.registerBeanDefinition(channelRegistryHolder, parserContext.getRegistry());

spring-integration-core/src/main/java/org/springframework/integration/config/xml/ChannelInitializer.java

@@ -24,20 +24,15 @@
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanDefinitionHolder;
-import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
-import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
-import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionReaderUtils;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
-import org.springframework.beans.factory.support.ManagedSet;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.integration.channel.DirectChannel;
 
 /**
  * A {@link InitializingBean} implementation that is responsible for creating
- * channels that are not explicitly defined but identified via 'input-channel'
+ * channels that are not explicitly defined but identified via the 'input-channel'
  * attribute of the corresponding endpoints.
  * 
  * This bean plays a role of pre-instantiator since it is instantiated and
@@ -90,44 +85,20 @@ public void afterPropertiesSet() throws Exception {
 			}
 		}
 	}
-	
+
 	/*
-	 * This class serves two purposes
-	 * 1. A BeanDefinition that collects candidate channel names as its BeanDefinition attributes
-	 * 2. A holder of the resolved (property placeholders and SpEL expressions) channel names to be auto-created by the 
-	 * ChannelInitializer.
-	 * Once this bean reaches Factory post processing phase it creates a new definition of itself injecting it with
-	 * the ManagedSet of channelNames property. The ManagedSet will be naturally resolved before it is used by the 
-	 * ChannelInitializer. It also unregisters its old definition (since its only value was to provide a place
-	 * to collect candidate channel names) and registers new definition of itself with "to-be resolved" channelNames
-	 * property
+	 * Collects candidate channel names to be auto-created by ChannelInitializer
 	 */
-	public static class AutoCreateCandidatesCollector implements BeanFactoryPostProcessor{
-		
-		private volatile Collection<String> channelNames;
-		
-		public void setChannelNames(Collection<String> channelNames) {
+	static class AutoCreateCandidatesCollector {
+
+		private final Collection<String> channelNames;
+
+		public AutoCreateCandidatesCollector(Collection<String> channelNames){
 			this.channelNames = channelNames;
 		}
 
 		public Collection<String> getChannelNames() {
 			return channelNames;
 		}
-
-		@SuppressWarnings("unchecked")
-		public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
-			BeanDefinition definition = beanFactory.getBeanDefinition(ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
-			Collection<String> _channelNames = (Collection<String>) definition.getAttribute(ChannelInitializer.CHANNEL_NAMES_ATTR);
-			if (_channelNames != null){
-				((BeanDefinitionRegistry)beanFactory).removeBeanDefinition(ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
-				BeanDefinitionBuilder candidatesBuilder = BeanDefinitionBuilder.genericBeanDefinition(this.getClass().getName());
-				ManagedSet<String> candidateChannelNamesToBeResolved = new ManagedSet<String>();
-				candidateChannelNamesToBeResolved.addAll(_channelNames);
-				candidatesBuilder.addPropertyValue("channelNames", candidateChannelNamesToBeResolved);
-				BeanDefinitionHolder holder = new BeanDefinitionHolder(candidatesBuilder.getBeanDefinition(), 
-						ChannelInitializer.AUTO_CREATE_CHANNEL_CANDIDATES_BEAN_NAME);
-				BeanDefinitionReaderUtils.registerBeanDefinition(holder, (BeanDefinitionRegistry) beanFactory);		
-			}
-		}
 	}
 }