INT-4518: Channel late-binding in Messaging Anns

JIRA: https://jira.spring.io/browse/INT-4518

* Fix `BridgeFromAnnotationPostProcessor` do not resolve `outputChannel`
for the target `BridgeHandler`
* Rework logic in the `AbstractMethodAnnotationPostProcessor` to do not
resolve a `MessageHandler` bean from the `@Bean` method when we can
just check a method return type.
* Check `BeanDefinition` instead of real bean when we consult for
conditions

**Cherry-pick to 5.0.x**

spring-integration-core/src/main/java/org/springframework/integration/config/annotation/AbstractMethodAnnotationPostProcessor.java

@@ -98,7 +98,7 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 
 	protected final Log logger = LogFactory.getLog(this.getClass());
 
-	protected final List<String> messageHandlerAttributes = new ArrayList<String>();
+	protected final List<String> messageHandlerAttributes = new ArrayList<>();
 
 	protected final ConfigurableListableBeanFactory beanFactory;
 
@@ -129,23 +129,21 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 	@Override
 	public Object postProcess(Object bean, String beanName, Method method, List<Annotation> annotations) {
 		if (this.beanAnnotationAware() && AnnotatedElementUtils.isAnnotated(method, Bean.class.getName())) {
-			try {
-				resolveTargetBeanFromMethodWithBeanAnnotation(method);
-			}
-			catch (NoSuchBeanDefinitionException e) {
-				if (this.logger.isDebugEnabled()) {
-					this.logger.debug("Skipping endpoint creation; "
-							+ e.getMessage()
-							+ "; perhaps due to some '@Conditional' annotation.");
-				}
+			if (!this.beanFactory.containsBeanDefinition(resolveTargetBeanName(method))) {
+				this.logger.debug("Skipping endpoint creation; perhaps due to some '@Conditional' annotation.");
 				return null;
 			}
 		}
 
-		List<Advice> adviceChain = extractAdviceChain(beanName, annotations);
+		boolean handlerExists = false;
+		if (beanAnnotationAware() && AnnotatedElementUtils.isAnnotated(method, Bean.class.getName())) {
+			handlerExists = MessageHandler.class.isAssignableFrom(method.getReturnType());
+		}
 
 		MessageHandler handler = createHandler(bean, method, annotations);
 
+		List<Advice> adviceChain = extractAdviceChain(beanName, annotations);
+
 		if (!CollectionUtils.isEmpty(adviceChain) && handler instanceof AbstractReplyProducingMessageHandler) {
 			((AbstractReplyProducingMessageHandler) handler).setAdviceChain(adviceChain);
 		}
@@ -169,12 +167,6 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 			}
 		}
 
-		boolean handlerExists = false;
-		if (this.beanAnnotationAware() && AnnotatedElementUtils.isAnnotated(method, Bean.class.getName())) {
-			Object handlerBean = this.resolveTargetBeanFromMethodWithBeanAnnotation(method);
-			handlerExists = handlerBean != null && handler == handlerBean;
-		}
-
 		if (!handlerExists) {
 			String handlerBeanName = generateHandlerBeanName(beanName, method);
 			if (handler instanceof ReplyProducingMessageHandlerWrapper
@@ -228,7 +220,9 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 		if (endpoint != null) {
 			return endpoint;
 		}
-		return handler;
+		else {
+			return handler;
+		}
 	}
 
 	@Override
@@ -450,14 +444,11 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 	}
 
 	protected String resolveTargetBeanName(Method method) {
-		String id = null;
+		String id = method.getName();
 		String[] names = AnnotationUtils.getAnnotation(method, Bean.class).name();
 		if (!ObjectUtils.isEmpty(names)) {
 			id = names[0];
 		}
-		if (!StringUtils.hasText(id)) {
-			id = method.getName();
-		}
 		return id;
 	}
 

spring-integration-core/src/main/java/org/springframework/integration/config/annotation/BridgeFromAnnotationPostProcessor.java

@@ -73,9 +73,8 @@ public class BridgeFromAnnotationPostProcessor extends AbstractMethodAnnotationP
 	@Override
 	protected MessageHandler createHandler(Object bean, Method method, List<Annotation> annotations) {
 		BridgeHandler handler = new BridgeHandler();
-		Object outputChannel = resolveTargetBeanFromMethodWithBeanAnnotation(method);
-		Assert.isInstanceOf(MessageChannel.class, outputChannel);
-		handler.setOutputChannel((MessageChannel) outputChannel);
+		String outputChannelName = resolveTargetBeanName(method);
+		handler.setOutputChannelName(outputChannelName);
 		return handler;
 	}
 

spring-integration-core/src/test/java/org/springframework/integration/config/annotation/BridgeFromIntegrationTests.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright 2018 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.integration.config.annotation;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.integration.annotation.BridgeFrom;
+import org.springframework.integration.channel.DirectChannel;
+import org.springframework.integration.channel.QueueChannel;
+import org.springframework.integration.config.EnableIntegration;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.PollableChannel;
+import org.springframework.messaging.support.GenericMessage;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringRunner;
+
+/**
+ * @author Artem Bilan
+ *
+ * @since 5.0.8
+ */
+@RunWith(SpringRunner.class)
+@ContextConfiguration(classes = BridgeFromIntegrationTests.RootTestConfiguration.class)
+public class BridgeFromIntegrationTests {
+
+	@Autowired
+	private MessageChannel gatewayChannel;
+
+	@Autowired
+	private PollableChannel outputChannel;
+
+	@Test
+	public void testBridgeFromConfiguration() {
+		this.gatewayChannel.send(new GenericMessage<>("world"));
+
+		Message<?> receive = this.outputChannel.receive(10_000);
+
+		assertNotNull(receive);
+		assertEquals("hello world", receive.getPayload());
+	}
+
+
+	@Configuration
+	@EnableIntegration
+	@ComponentScan(
+			basePackageClasses = BridgeFromIntegrationTests.class,
+			useDefaultFilters = false,
+			includeFilters = @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE,
+					classes = { AnnotatedTestService.class, ScannedTestConfiguration.class }))
+	public static class RootTestConfiguration {
+
+	}
+
+	@Configuration
+	public static class ScannedTestConfiguration {
+
+		@Bean
+		@BridgeFrom("gatewayChannel")
+		public DirectChannel inputChannel() {
+			return new DirectChannel();
+		}
+
+
+		@Bean
+		public DirectChannel gatewayChannel() {
+			return new DirectChannel();
+		}
+
+
+		@Bean
+		public PollableChannel outputChannel() {
+			return new QueueChannel();
+		}
+
+	}
+
+}