From dc6f5aa0047ef2938b2679da2cf8d5d5097b3d4d Mon Sep 17 00:00:00 2001
From: abilan <abilan@vmware.com>
Date: Mon, 28 Nov 2022 14:12:12 -0500
Subject: [PATCH] GH-3953: Use lazy-load for output channels

Fixes https://github.com/spring-projects/spring-integration/issues/3953

The replying `MessageHandler` can resolve the target output channel in on-demand manner.
A new messaging annotations on `@Bean` parsing algorithm is missing the lazy-load
opportunity and uses a `RuntimeBeanReference` for output channel options
loading its bean eagerly.

* Fix `AbstractMethodAnnotationPostProcessor` to use a `outputChannelName` and
`defaultOutputChannelName` target properties for channel names to set.
---
 ...AbstractMethodAnnotationPostProcessor.java |  4 +--
 ...ingAnnotationsWithBeanAnnotationTests.java | 35 +++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/spring-integration-core/src/main/java/org/springframework/integration/config/AbstractMethodAnnotationPostProcessor.java b/spring-integration-core/src/main/java/org/springframework/integration/config/AbstractMethodAnnotationPostProcessor.java
index 4645a58431..abd651d10c 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/config/AbstractMethodAnnotationPostProcessor.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/config/AbstractMethodAnnotationPostProcessor.java
@@ -211,8 +211,8 @@ public abstract class AbstractMethodAnnotationPostProcessor<T extends Annotation
 
 					new BeanDefinitionPropertiesMapper(handlerBeanDefinition, annotations)
 							.setPropertyValue(SEND_TIMEOUT_ATTRIBUTE)
-							.setPropertyReference("outputChannel")
-							.setPropertyReference("defaultOutputChannel");
+							.setPropertyValue("outputChannel", "outputChannelName")
+							.setPropertyValue("defaultOutputChannel", "defaultOutputChannelName");
 				}
 
 				if (isClassIn(handlerBeanClass, AbstractMessageProducingHandler.class,
diff --git a/spring-integration-core/src/test/java/org/springframework/integration/config/annotation/MessagingAnnotationsWithBeanAnnotationTests.java b/spring-integration-core/src/test/java/org/springframework/integration/config/annotation/MessagingAnnotationsWithBeanAnnotationTests.java
index 599dff2b96..290d1f96bb 100644
--- a/spring-integration-core/src/test/java/org/springframework/integration/config/annotation/MessagingAnnotationsWithBeanAnnotationTests.java
+++ b/spring-integration-core/src/test/java/org/springframework/integration/config/annotation/MessagingAnnotationsWithBeanAnnotationTests.java
@@ -47,6 +47,7 @@ import org.springframework.integration.aggregator.ExpressionEvaluatingCorrelatio
 import org.springframework.integration.aggregator.ExpressionEvaluatingReleaseStrategy;
 import org.springframework.integration.annotation.BridgeFrom;
 import org.springframework.integration.annotation.BridgeTo;
+import org.springframework.integration.annotation.EndpointId;
 import org.springframework.integration.annotation.Filter;
 import org.springframework.integration.annotation.InboundChannelAdapter;
 import org.springframework.integration.annotation.Poller;
@@ -63,6 +64,7 @@ import org.springframework.integration.config.EnableMessageHistory;
 import org.springframework.integration.context.IntegrationContextUtils;
 import org.springframework.integration.core.MessageSelector;
 import org.springframework.integration.core.MessageSource;
+import org.springframework.integration.dsl.IntegrationFlow;
 import org.springframework.integration.endpoint.AbstractEndpoint;
 import org.springframework.integration.endpoint.EventDrivenConsumer;
 import org.springframework.integration.endpoint.SourcePollingChannelAdapter;
@@ -70,7 +72,10 @@ import org.springframework.integration.filter.ExpressionEvaluatingSelector;
 import org.springframework.integration.history.MessageHistory;
 import org.springframework.integration.splitter.DefaultMessageSplitter;
 import org.springframework.integration.store.MessageGroup;
+import org.springframework.integration.test.util.TestUtils;
 import org.springframework.integration.transformer.ExpressionEvaluatingTransformer;
+import org.springframework.integration.transformer.MessageTransformingHandler;
+import org.springframework.integration.transformer.ObjectToMapTransformer;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
@@ -151,6 +156,10 @@ public class MessagingAnnotationsWithBeanAnnotationTests {
 	@Autowired
 	private CountDownLatch reactiveCustomizerLatch;
 
+	@Autowired
+	@Qualifier("objectToMapEndpoint.handler")
+	private MessageTransformingHandler objectToMapTransformerHandler;
+
 	@Test
 	public void testMessagingAnnotationsFlow() throws InterruptedException {
 		Stream.of(this.sourcePollingChannelAdapters).forEach(AbstractEndpoint::start);
@@ -253,6 +262,18 @@ public class MessagingAnnotationsWithBeanAnnotationTests {
 				.verifyComplete();
 	}
 
+	@Test
+	public void outputChannelIsLazyLoaded() {
+		assertThat(TestUtils.getPropertyValue(this.objectToMapTransformerHandler, "outputChannelName"))
+				.isEqualTo("lazilyCreatedChannel");
+
+		assertThat(TestUtils.getPropertyValue(this.objectToMapTransformerHandler, "outputChannel")).isNull();
+
+		assertThat(this.objectToMapTransformerHandler.getOutputChannel())
+				.isInstanceOf(DirectChannel.class)
+				.extracting("beanName")
+				.isEqualTo("lazilyCreatedChannel");
+	}
 
 	@Configuration
 	@EnableIntegration
@@ -460,6 +481,20 @@ public class MessagingAnnotationsWithBeanAnnotationTests {
 			};
 		}
 
+		@Bean
+		@Transformer(inputChannel = "toMapChannel", outputChannel = "lazilyCreatedChannel")
+		@EndpointId("objectToMapEndpoint")
+		public ObjectToMapTransformer objectToMapTransformer() {
+			return new ObjectToMapTransformer();
+		}
+
+		@Bean
+		public IntegrationFlow lazyChannelFlow() {
+			return IntegrationFlow.from("lazilyCreatedChannel")
+					.log()
+					.nullChannel();
+		}
+
 	}
 
 	@Configuration