Sonar Fixes

https://sonar.spring.io/component_issues?id=org.springframework.integration%3Aspring-integration%3Amaster#resolved=false|types=BUG

In `IntegrationFlowRegistration` double check locking is ok for `inputChannel`
because we're assigning an existing object, but `MessagingTemplate` constructs
a new object for which double check locking doesn't work.

In any case, for both these items, the chance of concurrent access is extremely low
and is idempotent anyway, so remove double check locking.

Several inner classes can be static.

Other minor fixes.

spring-integration-core/src/main/java/org/springframework/integration/channel/DefaultHeaderChannelRegistry.java

@@ -229,7 +229,7 @@ public class DefaultHeaderChannelRegistry extends IntegrationObjectSupport
 	}
 
 
-	private final class MessageChannelWrapper {
+	private static final class MessageChannelWrapper {
 
 		private final MessageChannel channel;
 

spring-integration-core/src/main/java/org/springframework/integration/channel/QueueChannel.java

@@ -119,7 +119,7 @@ public class QueueChannel extends AbstractPollableChannel implements QueueChanne
 					long nanos = TimeUnit.MILLISECONDS.toNanos(timeout);
 					long deadline = System.nanoTime() + nanos;
 					while (this.queue.size() == 0 && nanos > 0) {
-						this.queueSemaphore.tryAcquire(nanos, TimeUnit.NANOSECONDS);
+						this.queueSemaphore.tryAcquire(nanos, TimeUnit.NANOSECONDS); // NOSONAR - ok to ignore result
 						nanos = deadline - System.nanoTime();
 					}
 					return this.queue.poll();

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

@@ -84,7 +84,7 @@ public class ServiceActivatorAnnotationPostProcessor extends AbstractMethodAnnot
 		return serviceActivator;
 	}
 
-	private final class ReplyProducingMessageHandlerWrapper extends AbstractReplyProducingMessageHandler
+	private static final class ReplyProducingMessageHandlerWrapper extends AbstractReplyProducingMessageHandler
 			implements Lifecycle {
 
 		private final MessageHandler target;

spring-integration-core/src/main/java/org/springframework/integration/dsl/StandardIntegrationFlow.java

@@ -35,7 +35,7 @@ public class StandardIntegrationFlow implements IntegrationFlow, SmartLifecycle
 
 	private final List<SmartLifecycle> lifecycles = new LinkedList<SmartLifecycle>();
 
-	private final boolean registerComponents = true;
+	private final boolean registerComponents = true; // NOSONAR
 
 	private boolean running;
 
@@ -43,7 +43,7 @@ public class StandardIntegrationFlow implements IntegrationFlow, SmartLifecycle
 		this.integrationComponents = new LinkedList<Object>(integrationComponents);
 	}
 
-	//TODO Figure out some custom DestinationResolver when we don't register singletons
+	//TODO Figure out some custom DestinationResolver when we don't register singletons - remove NOSONAR above when done
 	/*public void setRegisterComponents(boolean registerComponents) {
 		this.registerComponents = registerComponents;
 	}*/

spring-integration-core/src/main/java/org/springframework/integration/dsl/context/IntegrationFlowRegistration.java

@@ -53,7 +53,7 @@ public class IntegrationFlowRegistration {
 	}
 
 	void setBeanFactory(ConfigurableListableBeanFactory beanFactory) {
-		this.beanFactory = beanFactory;
+		this.beanFactory = beanFactory; // NOSONAR (synchronization)
 	}
 
 	void setIntegrationFlowContext(IntegrationFlowContext integrationFlowContext) {
@@ -78,28 +78,24 @@ public class IntegrationFlowRegistration {
 
 	public MessageChannel getInputChannel() {
 		if (this.inputChannel == null) {
-			synchronized (this) {
-				if (this.inputChannel == null) {
-					if (this.integrationFlow instanceof StandardIntegrationFlow) {
-						StandardIntegrationFlow integrationFlow = (StandardIntegrationFlow) this.integrationFlow;
-						Object next = integrationFlow.getIntegrationComponents().iterator().next();
-						if (next instanceof MessageChannel) {
-							this.inputChannel = (MessageChannel) next;
-						}
-						else {
-							throw new IllegalStateException("The 'IntegrationFlow' [" + integrationFlow + "] " +
-									"doesn't start with 'MessageChannel' for direct message sending.");
-						}
-					}
-					else {
-						throw new IllegalStateException("Only 'StandardIntegrationFlow' instances " +
-								"(e.g. extracted from 'IntegrationFlow' Lambdas) can be used " +
-								"for direct 'send' operation. " +
-								"But [" + this.integrationFlow + "] ins't one of them.\n" +
-								"Consider 'BeanFactory.getBean()' usage for sending messages " +
-								"to the required 'MessageChannel'.");
-					}
+			if (this.integrationFlow instanceof StandardIntegrationFlow) {
+				StandardIntegrationFlow integrationFlow = (StandardIntegrationFlow) this.integrationFlow;
+				Object next = integrationFlow.getIntegrationComponents().iterator().next();
+				if (next instanceof MessageChannel) {
+					this.inputChannel = (MessageChannel) next;
 				}
+				else {
+					throw new IllegalStateException("The 'IntegrationFlow' [" + integrationFlow + "] " +
+							"doesn't start with 'MessageChannel' for direct message sending.");
+				}
+			}
+			else {
+				throw new IllegalStateException("Only 'StandardIntegrationFlow' instances " +
+						"(e.g. extracted from 'IntegrationFlow' Lambdas) can be used " +
+						"for direct 'send' operation. " +
+						"But [" + this.integrationFlow + "] ins't one of them.\n" +
+						"Consider 'BeanFactory.getBean()' usage for sending messages " +
+						"to the required 'MessageChannel'.");
 			}
 		}
 		return this.inputChannel;
@@ -115,25 +111,21 @@ public class IntegrationFlowRegistration {
 	 */
 	public MessagingTemplate getMessagingTemplate() {
 		if (this.messagingTemplate == null) {
-			synchronized (this) {
-				if (this.messagingTemplate == null) {
-					this.messagingTemplate = new MessagingTemplate(getInputChannel()) {
+			this.messagingTemplate = new MessagingTemplate(getInputChannel()) {
 
-						@Override
-						public Message<?> receive() {
-							return receiveAndConvert(Message.class);
-						}
-
-						@Override
-						public <T> T receiveAndConvert(Class<T> targetClass) {
-							throw new UnsupportedOperationException("The 'receive()/receiveAndConvert()' " +
-									"isn't supported on the 'IntegrationFlow' input channel.");
-						}
-
-					};
-					this.messagingTemplate.setBeanFactory(this.beanFactory);
+				@Override
+				public Message<?> receive() {
+					return receiveAndConvert(Message.class);
 				}
-			}
+
+				@Override
+				public <T> T receiveAndConvert(Class<T> targetClass) {
+					throw new UnsupportedOperationException("The 'receive()/receiveAndConvert()' " +
+							"isn't supported on the 'IntegrationFlow' input channel.");
+				}
+
+			};
+			this.messagingTemplate.setBeanFactory(this.beanFactory);
 		}
 		return this.messagingTemplate;
 	}

spring-integration-core/src/main/java/org/springframework/integration/store/SimpleMessageStore.java

@@ -278,13 +278,13 @@ public class SimpleMessageStore extends AbstractMessageGroupStore
 						throw outOfCapacityException;
 					}
 					group = getMessageGroupFactory().create(groupId);
-					this.groupIdToMessageGroup.putIfAbsent(groupId, group);
+					this.groupIdToMessageGroup.put(groupId, group);
 					upperBound = new UpperBound(this.groupCapacity);
 					for (Message<?> message : messages) {
 						upperBound.tryAcquire(-1);
 						group.add(message);
 					}
-					this.groupToUpperBound.putIfAbsent(groupId, upperBound);
+					this.groupToUpperBound.put(groupId, upperBound);
 				}
 				else {
 					upperBound = this.groupToUpperBound.get(groupId);

spring-integration-core/src/main/java/org/springframework/integration/support/converter/SimpleMessageConverter.java

@@ -141,7 +141,7 @@ public class SimpleMessageConverter implements MessageConverter, BeanFactoryAwar
 	}
 
 
-	private class DefaultOutboundMessageMapper implements OutboundMessageMapper<Object> {
+	private static class DefaultOutboundMessageMapper implements OutboundMessageMapper<Object> {
 
 		DefaultOutboundMessageMapper() {
 			super();

spring-integration-core/src/main/java/org/springframework/integration/util/SimplePool.java

@@ -122,18 +122,22 @@ public class SimplePool<T> implements Pool<T> {
 	 * if it was recently reduced and too many items were in use to allow the new size
 	 * to be set.
 	 */
-	public int getPoolSize() {
+	@Override
+	public synchronized int getPoolSize() {
 		return this.poolSize.get();
 	}
 
+	@Override
 	public int getIdleCount() {
 		return this.available.size();
 	}
 
+	@Override
 	public int getActiveCount() {
 		return this.inUse.size();
 	}
 
+	@Override
 	public int getAllocatedCount() {
 		return this.allocated.size();
 	}
@@ -153,6 +157,7 @@ public class SimplePool<T> implements Pool<T> {
 	 * Obtains an item from the pool; waits up to waitTime milliseconds (default infinity).
 	 * @throws MessagingException if no items become available in time.
 	 */
+	@Override
 	public T getItem() {
 		boolean permitted = false;
 		try {
@@ -205,6 +210,7 @@ public class SimplePool<T> implements Pool<T> {
 	/**
 	 * Returns an item to the pool.
 	 */
+	@Override
 	public synchronized void releaseItem(T item) {
 		Assert.notNull(item, "Item cannot be null");
 		Assert.isTrue(this.allocated.contains(item),
@@ -234,6 +240,7 @@ public class SimplePool<T> implements Pool<T> {
 		}
 	}
 
+	@Override
 	public synchronized void removeAllIdleItems() {
 		T item;
 		while ((item = this.available.poll()) != null) {