Re-instate lazy lookup for Binder in DestinationResolver

It's important not to depend on something heavyweight like a Binder
in a BeanPostProcessor. The usual trick (as implemented here) is
to do a lazy lookup of the thing that is eventually injected in the
post processes beans.

Fixes gh-82

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/BinderAwareRouterBeanPostProcessor.java

@@ -17,31 +17,26 @@
 package org.springframework.cloud.stream.binder;
 
 import org.springframework.beans.BeansException;
-import org.springframework.beans.factory.BeanFactory;
-import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.integration.router.AbstractMappingMessageRouter;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.core.DestinationResolver;
 
 /**
  * A {@link BeanPostProcessor} that sets a {@link BinderAwareChannelResolver} on any bean of type
  * {@link AbstractMappingMessageRouter} within the context.
- * 
+ *
  * @author Mark Fisher
  * @author Gary Russell
  */
-public class BinderAwareRouterBeanPostProcessor implements BeanPostProcessor, BeanFactoryAware {
+public class BinderAwareRouterBeanPostProcessor implements BeanPostProcessor {
 
-	private final BinderAwareChannelResolver channelResolver;
+	private final DestinationResolver<MessageChannel> channelResolver;
 
-	public BinderAwareRouterBeanPostProcessor(BinderAwareChannelResolver channelResolver) {
+	public BinderAwareRouterBeanPostProcessor(DestinationResolver<MessageChannel> channelResolver) {
 		this.channelResolver = channelResolver;
 	}
 
-	@Override
-	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
-		channelResolver.setBeanFactory(beanFactory);
-	}
-
 	@Override
 	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
 		return bean;
@@ -50,7 +45,7 @@ public class BinderAwareRouterBeanPostProcessor implements BeanPostProcessor, Be
 	@Override
 	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
 		if (bean instanceof AbstractMappingMessageRouter) {
-			((AbstractMappingMessageRouter) bean).setChannelResolver(channelResolver);
+			((AbstractMappingMessageRouter) bean).setChannelResolver(this.channelResolver);
 		}
 		return bean;
 	}

spring-cloud-stream/src/main/java/org/springframework/cloud/stream/config/ChannelBindingAdapterConfiguration.java

@@ -38,6 +38,8 @@ import org.springframework.cloud.stream.endpoint.ChannelsEndpoint;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.core.DestinationResolutionException;
+import org.springframework.messaging.core.DestinationResolver;
 
 /**
  * Configuration class that provides necessary beans for {@link MessageChannel} binding.
@@ -61,8 +63,9 @@ public class ChannelBindingAdapterConfiguration {
 
 	@Bean
 	public ChannelBindingAdapter bindingAdapter() {
-		ChannelBindingAdapter adapter = new ChannelBindingAdapter(this.module, this.binder);
-		adapter.setChannelLocator(new DefaultChannelLocator(module));
+		ChannelBindingAdapter adapter = new ChannelBindingAdapter(this.module,
+				this.binder);
+		adapter.setChannelLocator(new DefaultChannelLocator(this.module));
 		adapter.setOutputChannels(getOutputChannels());
 		adapter.setInputChannels(getInputChannels());
 		adapter.setChannelResolver(binderAwareChannelResolver());
@@ -81,7 +84,8 @@ public class ChannelBindingAdapterConfiguration {
 			BeanDefinition beanDefinition = this.beanFactory.getBeanDefinition(name);
 			// for now, just assume that the beans are at least AbstractBeanDefinition
 			if (beanDefinition instanceof AbstractBeanDefinition
-					&& ((AbstractBeanDefinition) beanDefinition).getQualifier(Output.class.getName()) != null) {
+					&& ((AbstractBeanDefinition) beanDefinition)
+					.getQualifier(Output.class.getName()) != null) {
 				channels.add(new OutputChannelBinding(name));
 			}
 		}
@@ -95,7 +99,8 @@ public class ChannelBindingAdapterConfiguration {
 			BeanDefinition beanDefinition = this.beanFactory.getBeanDefinition(name);
 			// for now, just assume that the beans are at least AbstractBeanDefinition
 			if (beanDefinition instanceof AbstractBeanDefinition
-					&& ((AbstractBeanDefinition) beanDefinition).getQualifier(Input.class.getName()) != null) {
+					&& ((AbstractBeanDefinition) beanDefinition).getQualifier(Input.class
+							.getName()) != null) {
 				channels.add(new InputChannelBinding(name));
 			}
 		}
@@ -104,11 +109,35 @@ public class ChannelBindingAdapterConfiguration {
 
 	@Bean
 	public BinderAwareChannelResolver binderAwareChannelResolver() {
-		return new BinderAwareChannelResolver(BeanFactoryUtils.beanOfType(beanFactory, Binder.class), new Properties());
+		return new BinderAwareChannelResolver(this.binder, new Properties());
 	}
 
-	@Bean
-	public BinderAwareRouterBeanPostProcessor binderAwareRouterBeanPostProcessor(BinderAwareChannelResolver resolver) {
-		return new BinderAwareRouterBeanPostProcessor(resolver);
+	// IMPORTANT: Nested class to avoid instantiating all of the above early
+	@Configuration
+	protected static class PostProcessorConfiguration {
+
+		private BinderAwareChannelResolver binderAwareChannelResolver;
+
+		@Bean
+		public BinderAwareRouterBeanPostProcessor binderAwareRouterBeanPostProcessor(
+				final ConfigurableListableBeanFactory beanFactory) {
+			// IMPORTANT: Lazy delegate to avoid instantiating all of the above early
+			return new BinderAwareRouterBeanPostProcessor(
+					new DestinationResolver<MessageChannel>() {
+
+						@Override
+						public MessageChannel resolveDestination(String name)
+								throws DestinationResolutionException {
+							if (PostProcessorConfiguration.this.binderAwareChannelResolver == null) {
+								PostProcessorConfiguration.this.binderAwareChannelResolver = BeanFactoryUtils.beanOfType(
+										beanFactory, BinderAwareChannelResolver.class);
+							}
+							return PostProcessorConfiguration.this.binderAwareChannelResolver.resolveDestination(name);
+						}
+
+					});
+		}
+
 	}
+
 }