Refactor shutdown deferral logic based on review feedback

- Move @nullable to type declaration
- Use pattern matching for ListenerContainerAware
- Skip waiting when replyCounter is null or count is zero
- Extract shutdown wait logic into separate method
- Add author tag and update whats-new.adoc

Signed-off-by: Jeongjun Min <[email protected]>

Author: m3k0813

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/core/RabbitTemplate.java

@@ -159,6 +159,7 @@
  * @author Alexey Platonov
  * @author Leonardo Ferreira
  * @author Ngoc Nhan
+ * @author Jeongjun Min
  *
  * @since 1.0
  */

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/listener/SimpleMessageListenerContainer.java

@@ -87,6 +87,7 @@
  * @author Jeonggi Kim
  * @author Java4ye
  * @author Thomas Badie
+ * @author Jeongjun Min
  *
  * @since 1.0
  */
@@ -692,22 +693,8 @@ protected void shutdownAndWaitOrCallback(@Nullable Runnable callback) {
 		Runnable awaitShutdown = () -> {
 			logger.info("Waiting for workers to finish.");
 			try {
-				ActiveObjectCounter<Object> replyCounter = null;
-				Object listener = getMessageListener();
-				if (listener instanceof ListenerContainerAware) {
-					replyCounter = ((ListenerContainerAware) listener).getPendingReplyCounter();
-				}
-
-				if (replyCounter != null) {
-					if (logger.isInfoEnabled()) {
-						logger.info("Waiting for pending replies: " + replyCounter.getCount());
-					}
-					if (!replyCounter.await(getShutdownTimeout(), TimeUnit.MILLISECONDS)) {
-						if (logger.isWarnEnabled()) {
-							logger.warn("Shutdown timeout expired, but " + replyCounter.getCount()
-									+ " pending replies still remain.");
-						}
-					}
+				if (getMessageListener() instanceof ListenerContainerAware listenerContainerAware) {
+					awaitPendingReplies(listenerContainerAware);
 				}
 
 				boolean finished = this.cancellationLock.await(getShutdownTimeout(), TimeUnit.MILLISECONDS);
@@ -756,6 +743,22 @@ private void runCallbackIfNotNull(@Nullable Runnable callback) {
 		}
 	}
 
+	private void awaitPendingReplies(ListenerContainerAware listener) throws InterruptedException {
+		ActiveObjectCounter<Object> replyCounter = listener.getPendingReplyCounter();
+
+		if (replyCounter != null && replyCounter.getCount() > 0) {
+			if (logger.isInfoEnabled()) {
+				logger.info("Waiting for pending replies: " + replyCounter.getCount());
+			}
+			if (!replyCounter.await(getShutdownTimeout(), TimeUnit.MILLISECONDS)) {
+				if (logger.isWarnEnabled()) {
+					logger.warn("Shutdown timeout expired, but " + replyCounter.getCount()
+							+ " pending replies still remain.");
+				}
+			}
+		}
+	}
+
 	private boolean isActive(BlockingQueueConsumer consumer) {
 		boolean consumerActive;
 		this.consumersLock.lock();

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/support/ListenerContainerAware.java

@@ -25,6 +25,7 @@
  * interface can have configuration verified during initialization.
  *
  * @author Gary Russell
+ * @author Jeongjun Min
  * @since 1.5
  *
  */
@@ -44,8 +45,7 @@ public interface ListenerContainerAware {
 	 * @return the counter, or null.
 	 * @since 4.0
 	 */
-	@Nullable
-	default ActiveObjectCounter<Object> getPendingReplyCounter() {
+	default @Nullable ActiveObjectCounter<Object> getPendingReplyCounter() {
 		return null;
 	}
 }

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/listener/SimpleMessageListenerContainerTests.java

@@ -104,6 +104,7 @@
  * @author Yansong Ren
  * @author Tim Bourquin
  * @author Jeonggi Kim
+ * @author Jeongjun Min
  */
 public class SimpleMessageListenerContainerTests {
 

src/reference/antora/modules/ROOT/pages/whats-new.adoc

@@ -36,4 +36,9 @@ There is no need to keep out-dated utilities and recommendation is to migrate to
 The Jackson 2 has been deprecated for removal in whole Spring portfolio.
 Respective new classes have been introduced to support Jackson 3.
 
-See xref:amqp/message-converters.adoc[] for more information.
+See xref:amqp/message-converters.adoc[] for more information.
+
+[[x40-enhancements]]
+=== Enhancements
+
+Defer `SimpleMessageListenerContainer` shutdown for pending `RabbitTemplate` replies.