Sonar fixes

* use equals
* inner assignment
* local before return
* unnecessary locals
* catch and throw
* uninstantiable with no statics
* implement `Serializable` in `Comparator` to enable `TreeMap` serialization
* exceptions as flow control

Author: garyrussell

spring-integration-core/src/main/java/org/springframework/integration/aggregator/CorrelatingMessageBarrier.java

@@ -108,6 +108,7 @@ private Object getLock(Object correlationKey) {
 	}
 
 
+	@SuppressWarnings("unchecked")
 	@Override
 	public Message<Object> receive() {
 		for (Object key : this.correlationLocks.keySet()) {
@@ -130,9 +131,7 @@ public Message<Object> receive() {
 						else {
 							remove(key);
 						}
-						@SuppressWarnings("unchecked")
-						Message<Object> result = (Message<Object>) nextMessage;
-						return result;
+						return (Message<Object>) nextMessage;
 					}
 				}
 			}

spring-integration-core/src/main/java/org/springframework/integration/aggregator/MessageSequenceComparator.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.aggregator;
 
+import java.io.Serializable;
 import java.util.Comparator;
 
 import org.springframework.integration.IntegrationMessageHeaderAccessor;
@@ -25,8 +26,10 @@
  * @author Mark Fisher
  * @author Dave Syer
  * @author Artem Bilan
+ * @author Gary Russell
  */
-public class MessageSequenceComparator implements Comparator<Message<?>> {
+@SuppressWarnings("serial")
+public class MessageSequenceComparator implements Comparator<Message<?>>, Serializable {
 
 	@Override
 	public int compare(Message<?> o1, Message<?> o2) {

spring-integration-core/src/main/java/org/springframework/integration/aop/PublisherAnnotationAdvisor.java

@@ -193,7 +193,7 @@ public boolean matches(Method method, Class<?> targetClass) {
 			}
 			// The method may be on an interface, so let's check on the target class as well.
 			Method specificMethod = AopUtils.getMostSpecificMethod(method, targetClass);
-			return (specificMethod != method &&
+			return (!specificMethod.equals(method) &&
 					(AnnotationUtils.getAnnotation(specificMethod, this.annotationType) != null));
 		}
 

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

@@ -106,7 +106,8 @@ public void subscribe(Subscriber<? super Message<T>> subscriber) {
 					.<Message<T>>create(sink ->
 									sink.onRequest(n -> {
 										Message<?> m;
-										while (!sink.isCancelled() && n-- > 0 && (m = this.channel.receive()) != null) {
+										while (!sink.isCancelled() && n-- > 0
+												&& (m = this.channel.receive()) != null) { // NOSONAR
 											sink.next((Message<T>) m);
 										}
 									}),

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

@@ -39,7 +39,7 @@ public final class FixedSubscriberChannelBeanFactoryPostProcessor implements Bea
 
 	private final Map<String, String> candidateFixedChannelHandlerMap;
 
-	private FixedSubscriberChannelBeanFactoryPostProcessor(Map<String, String> candidateHandlers) {
+	FixedSubscriberChannelBeanFactoryPostProcessor(Map<String, String> candidateHandlers) {
 		this.candidateFixedChannelHandlerMap = candidateHandlers;
 	}
 

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

@@ -158,7 +158,7 @@ public Object postProcess(Object bean, String beanName, Method method, List<Anno
 		orderable(method, handler);
 		producerOrRouter(annotations, handler);
 
-		if (handler != sourceHandler) {
+		if (!handler.equals(sourceHandler)) {
 			String handlerBeanName = generateHandlerBeanName(beanName, method);
 			if (handler instanceof ReplyProducingMessageHandlerWrapper
 					&& StringUtils.hasText(MessagingAnnotationUtils.endpointIdValue(method))) {

spring-integration-core/src/main/java/org/springframework/integration/config/xml/PointToPointChannelParser.java

@@ -52,7 +52,7 @@ protected BeanDefinitionBuilder buildBeanDefinition(Element element, ParserConte
 
 		// configure a queue-based channel if any queue sub-element is defined
 		String channel = element.getAttribute(ID_ATTRIBUTE);
-		if ((queueElement = DomUtils.getChildElementByTagName(element, "queue")) != null) {
+		if ((queueElement = DomUtils.getChildElementByTagName(element, "queue")) != null) { // NOSONAR inner assignment
 			builder = BeanDefinitionBuilder.genericBeanDefinition(QueueChannel.class);
 			boolean hasStoreRef = this.parseStoreRef(builder, queueElement, channel, false);
 			boolean hasQueueRef = this.parseQueueRef(builder, queueElement);
@@ -76,7 +76,7 @@ protected BeanDefinitionBuilder buildBeanDefinition(Element element, ParserConte
 						element);
 			}
 		}
-		else if ((queueElement = DomUtils.getChildElementByTagName(element, "priority-queue")) != null) {
+		else if ((queueElement = DomUtils.getChildElementByTagName(element, "priority-queue")) != null) { // NOSONAR
 			builder = BeanDefinitionBuilder.genericBeanDefinition(PriorityChannel.class);
 			boolean hasCapacity = this.parseQueueCapacity(builder, queueElement);
 			String comparatorRef = queueElement.getAttribute("comparator");
@@ -97,7 +97,7 @@ else if ((queueElement = DomUtils.getChildElementByTagName(element, "priority-qu
 			}
 
 		}
-		else if ((queueElement = DomUtils.getChildElementByTagName(element, "rendezvous-queue")) != null) {
+		else if ((queueElement = DomUtils.getChildElementByTagName(element, "rendezvous-queue")) != null) { // NOSONAR
 			builder = BeanDefinitionBuilder.genericBeanDefinition(RendezvousChannel.class);
 		}
 

spring-integration-core/src/main/java/org/springframework/integration/config/xml/SelectorChainParser.java

@@ -35,6 +35,7 @@
  *
  * @author Mark Fisher
  * @author Iwein Fuld
+ * @author Gary Russell
  */
 public class SelectorChainParser extends AbstractSingleBeanDefinitionParser {
 
@@ -43,6 +44,7 @@ protected String getBeanClassName(Element element) {
 		return MessageSelectorChain.class.getName();
 	}
 
+	@Override
 	public void doParse(Element element, ParserContext parserContext, BeanDefinitionBuilder builder) {
 		if (!StringUtils.hasText(element.getAttribute("id"))) {
 			parserContext.getReaderContext().error("id is required", element);
@@ -82,8 +84,7 @@ private RuntimeBeanReference buildSelectorChain(ParserContext parserContext, Nod
 		this.parseSelectorChain(nestedBuilder, (Element) child, parserContext);
 		String nestedBeanName = BeanDefinitionReaderUtils.registerWithGeneratedName(nestedBuilder.getBeanDefinition(),
 				parserContext.getRegistry());
-		RuntimeBeanReference built = new RuntimeBeanReference(nestedBeanName);
-		return built;
+		return new RuntimeBeanReference(nestedBeanName);
 	}
 
 	private RuntimeBeanReference buildMethodInvokingSelector(ParserContext parserContext, String ref, String method) {

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

@@ -59,7 +59,7 @@ public final class StandardIntegrationFlowContext implements IntegrationFlowCont
 
 	private BeanDefinitionRegistry beanDefinitionRegistry;
 
-	private StandardIntegrationFlowContext() {
+	StandardIntegrationFlowContext() {
 	}
 
 	@Override

spring-integration-core/src/main/java/org/springframework/integration/router/RecipientListRouter.java

@@ -137,15 +137,15 @@ public void addRecipient(String channelName, String selectorExpression) {
 		addRecipient(channelName, selectorExpression, this.recipients);
 	}
 
-	private void addRecipient(String channelName, String selectorExpression, Queue<Recipient> recipients) {
+	private void addRecipient(String channelName, String selectorExpression, Queue<Recipient> recipientsToAdd) {
 		Assert.hasText(channelName, "'channelName' must not be empty.");
 		Assert.hasText(selectorExpression, "'selectorExpression' must not be empty.");
 		ExpressionEvaluatingSelector expressionEvaluatingSelector =
 				new ExpressionEvaluatingSelector(selectorExpression);
 		expressionEvaluatingSelector.setBeanFactory(getBeanFactory());
 		Recipient recipient = new Recipient(channelName, expressionEvaluatingSelector);
 		setupRecipient(recipient);
-		recipients.add(recipient);
+		recipientsToAdd.add(recipient);
 	}
 
 	@Override
@@ -158,11 +158,11 @@ public void addRecipient(String channelName, MessageSelector selector) {
 		addRecipient(channelName, selector, this.recipients);
 	}
 
-	private void addRecipient(String channelName, MessageSelector selector, Queue<Recipient> recipients) {
+	private void addRecipient(String channelName, MessageSelector selector, Queue<Recipient> recipientsToAdd) {
 		Assert.hasText(channelName, "'channelName' must not be empty.");
 		Recipient recipient = new Recipient(channelName, selector);
 		setupRecipient(recipient);
-		recipients.add(recipient);
+		recipientsToAdd.add(recipient);
 	}
 
 	public void addRecipient(MessageChannel channel) {
@@ -208,9 +208,9 @@ public int removeRecipient(String channelName, String selectorExpression) {
 			Recipient next = it.next();
 			MessageSelector selector = next.getSelector();
 			MessageChannel channel = next.getChannel();
-			if (selector instanceof ExpressionEvaluatingSelector &&
-					channel == targetChannel &&
-					((ExpressionEvaluatingSelector) selector).getExpressionString().equals(selectorExpression)) {
+			if (selector instanceof ExpressionEvaluatingSelector
+					&& channel.equals(targetChannel)
+					&& ((ExpressionEvaluatingSelector) selector).getExpressionString().equals(selectorExpression)) {
 				it.remove();
 				counter++;
 			}