From d8fb02306f6fbb6a273d69d4eb0a57e21d1adef2 Mon Sep 17 00:00:00 2001
From: Artem Bilan <artem.bilan@broadcom.com>
Date: Tue, 10 Dec 2024 16:34:29 -0500
Subject: [PATCH] GH-9709: Fix `IntegrationFlow` for input channel resolution

Fixes: #9709
Issue link: https://github.com/spring-projects/spring-integration/issues/9709

The Java DSL loses an `inputChannel` when existing channel is referenced by its name.
Then the target IntegrationFlow does not contain a bean reference for this channel and when we call its `getInputChannel()` we got something from middle of the flow.
However, that `inputChannel` is really expected to be an input for the flow.

* Fix `IntegrationFlowBeanPostProcessor` to get a bean by `MessageChannelReference` and populate it into `targetIntegrationComponents`
as we do for newly created `DirectChannel` if there is no bean for provided `MessageChannelReference`

# Conflicts:
#	spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowBeanPostProcessor.java
---
 .../context/IntegrationFlowBeanPostProcessor.java    | 11 ++++++++---
 .../composition/IntegrationFlowCompositionTests.java | 12 +++++++++---
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowBeanPostProcessor.java b/spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowBeanPostProcessor.java
index b746627c83..3386fe7392 100644
--- a/spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowBeanPostProcessor.java
+++ b/spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowBeanPostProcessor.java
@@ -74,6 +74,7 @@ import org.springframework.integration.dsl.support.MessageChannelReference;
 import org.springframework.integration.gateway.AnnotationGatewayProxyFactoryBean;
 import org.springframework.integration.support.context.NamedComponent;
 import org.springframework.lang.Nullable;
+import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.MessageHandler;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -181,11 +182,15 @@ public class IntegrationFlowBeanPostProcessor
 			}
 			else if (component instanceof MessageChannelReference messageChannelReference) {
 				String channelBeanName = messageChannelReference.name();
+				MessageChannel channelByName;
 				if (!this.beanFactory.containsBean(channelBeanName)) {
-					DirectChannel directChannel = new DirectChannel();
-					registerComponent(directChannel, channelBeanName, flowBeanName);
-					targetIntegrationComponents.put(directChannel, channelBeanName);
+					channelByName = new DirectChannel();
+					registerComponent(channelByName, channelBeanName, flowBeanName);
 				}
+				else {
+					channelByName = this.beanFactory.getBean(channelBeanName, MessageChannel.class);
+				}
+				targetIntegrationComponents.put(channelByName, channelBeanName);
 			}
 			else if (component instanceof SourcePollingChannelAdapterSpec spec) {
 				Map<Object, String> componentsToRegister = spec.getComponentsToRegister();
diff --git a/spring-integration-core/src/test/java/org/springframework/integration/dsl/composition/IntegrationFlowCompositionTests.java b/spring-integration-core/src/test/java/org/springframework/integration/dsl/composition/IntegrationFlowCompositionTests.java
index d3413cacf1..ee84fef3ae 100644
--- a/spring-integration-core/src/test/java/org/springframework/integration/dsl/composition/IntegrationFlowCompositionTests.java
+++ b/spring-integration-core/src/test/java/org/springframework/integration/dsl/composition/IntegrationFlowCompositionTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2021-2023 the original author or authors.
+ * Copyright 2021-2024 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.
@@ -202,11 +202,17 @@ public class IntegrationFlowCompositionTests {
 					.to(lastFlow);
 		}
 
+		@Bean
+		DirectChannel lastFlowInput() {
+			return new DirectChannel();
+		}
+
 		@Bean
 		IntegrationFlow lastFlow() {
-			return f -> f
+			return IntegrationFlow.from("lastFlowInput")
 					.<String, String>transform(p -> p + ", and last flow")
-					.channel(c -> c.queue("lastFlowResult"));
+					.channel(c -> c.queue("lastFlowResult"))
+					.get();
 		}
 
 	}