From b865f3cbe9aeaf0feceaf013a947dfa4c1c79044 Mon Sep 17 00:00:00 2001
From: Gary Russell <grussell@pivotal.io>
Date: Fri, 10 Nov 2017 13:36:09 -0500
Subject: [PATCH] RGH-83: Allow binders to add interceptors

Resolves https://github.com/spring-cloud/spring-cloud-stream-binder-rabbit/issues/83

The RabbitMQ binder needs to add an interceptor to evaluate expressions (if they
include `payload`) before the payload is serialized.

Add a hook to allow the binder to post-process the message channel.

Resolves #1134
---
 .../cloud/stream/binder/AbstractBinder.java           |  4 ++--
 .../stream/binder/AbstractMessageChannelBinder.java   | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractBinder.java b/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractBinder.java
index 7df341865..a90e027c6 100644
--- a/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractBinder.java
+++ b/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractBinder.java
@@ -97,8 +97,8 @@ public abstract class AbstractBinder<T, C extends ConsumerProperties, P extends
 		return this.applicationContext.getBeanFactory();
 	}
 
-	public void setIntegrationEvaluationContext(EvaluationContext evaluationContext) {
-		this.evaluationContext = evaluationContext;
+	protected EvaluationContext getEvaluationContext() {
+		return this.evaluationContext;
 	}
 
 	@Override
diff --git a/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractMessageChannelBinder.java b/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractMessageChannelBinder.java
index 91ecc5e6e..ed8a0fd3c 100644
--- a/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractMessageChannelBinder.java
+++ b/spring-cloud-stream/src/main/java/org/springframework/cloud/stream/binder/AbstractMessageChannelBinder.java
@@ -138,6 +138,7 @@ public abstract class AbstractMessageChannelBinder<C extends ConsumerProperties,
 		if (producerMessageHandler instanceof Lifecycle) {
 			((Lifecycle) producerMessageHandler).start();
 		}
+		postProcessOutputChannel(outputChannel, producerProperties);
 		((SubscribableChannel) outputChannel).subscribe(
 				new SendingHandler(producerMessageHandler, HeaderMode.embeddedHeaders
 						.equals(producerProperties.getHeaderMode()), this.headersToEmbed,
@@ -163,6 +164,16 @@ public abstract class AbstractMessageChannelBinder<C extends ConsumerProperties,
 		};
 	}
 
+	/**
+	 * Allows subclasses to perform post processing on the channel - for example to
+	 * add more interceptors.
+	 * @param outputChannel the channel.
+	 * @param producerProperties the producer properties.
+	 */
+	protected void postProcessOutputChannel(MessageChannel outputChannel, P producerProperties) {
+		// default no-op
+	}
+
 	/**
 	 * Creates a {@link MessageHandler} with the ability to send data to the target
 	 * middleware. If the returned instance is also a {@link Lifecycle}, it will be