GH-10083 Add Nullability to core router

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

@@ -37,6 +37,7 @@
 import org.springframework.integration.router.MethodInvokingRouter;
 import org.springframework.integration.util.MessagingAnnotationUtils;
 import org.springframework.messaging.MessageHandler;
+import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -169,6 +170,7 @@ private void routerAttributes(List<Annotation> annotations, AbstractMessageRoute
 				}
 				Properties properties = (Properties) getConversionService().convert(mappings.toString(),
 						TypeDescriptor.valueOf(String.class), TypeDescriptor.valueOf(Properties.class));
+				Assert.state(properties != null, "The properties for channel mappings must not be null.");
 				methodInvokingRouter.replaceChannelMappings(properties);
 			}
 

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

@@ -27,6 +27,8 @@
 import java.util.Properties;
 import java.util.Set;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.log.LogMessage;
 import org.springframework.integration.support.management.MappingMessageRouterManagement;
@@ -50,6 +52,7 @@
  * @author Artem Bilan
  * @author Trung Pham
  * @author Ngoc Nhan
+ * @author Glenn Renfro
  *
  * @since 2.1
  */
@@ -72,9 +75,9 @@ protected boolean removeEldestEntry(Entry<String, MessageChannel> eldest) {
 
 					});
 
-	private String prefix;
+	private @Nullable String prefix;
 
-	private String suffix;
+	private @Nullable String suffix;
 
 	private boolean resolutionRequired = true;
 
@@ -104,15 +107,15 @@ public void setChannelMappings(Map<String, String> channelMappings) {
 	 * Specify a prefix to be added to each channel name prior to resolution.
 	 * @param prefix The prefix.
 	 */
-	public void setPrefix(String prefix) {
+	public void setPrefix(@Nullable String prefix) {
 		this.prefix = prefix;
 	}
 
 	/**
 	 * Specify a suffix to be added to each channel name prior to resolution.
 	 * @param suffix The suffix.
 	 */
-	public void setSuffix(String suffix) {
+	public void setSuffix(@Nullable String suffix) {
 		this.suffix = suffix;
 	}
 
@@ -274,7 +277,7 @@ protected Collection<MessageChannel> determineTargetChannels(Message<?> message)
 	 * @param message The message.
 	 * @return The channel keys.
 	 */
-	protected abstract List<Object> getChannelKeys(Message<?> message);
+	protected abstract @Nullable List<Object> getChannelKeys(Message<?> message);
 
 	/**
 	 * Convenience method allowing conversion of a list
@@ -289,7 +292,6 @@ protected Collection<MessageChannel> determineTargetChannels(Message<?> message)
 	@Override
 	@ManagedOperation
 	public void replaceChannelMappings(Properties channelMappings) {
-		Assert.notNull(channelMappings, "'channelMappings' must not be null");
 		Map<String, String> newChannelMappings = new LinkedHashMap<>();
 		Set<String> keys = channelMappings.stringPropertyNames();
 		for (String key : keys) {
@@ -304,7 +306,7 @@ private void doSetChannelMappings(Map<String, String> newChannelMappings) {
 		logger.debug(LogMessage.format("Channel mappings: %s replaced with: %s", oldChannelMappings, newChannelMappings));
 	}
 
-	private MessageChannel resolveChannelForName(String channelName, Message<?> message) {
+	private @Nullable MessageChannel resolveChannelForName(String channelName, Message<?> message) {
 		MessageChannel channel = null;
 		try {
 			channel = getChannelResolver().resolveDestination(channelName);
@@ -360,7 +362,7 @@ private void addChannel(Collection<MessageChannel> channels, Message<?> message,
 		}
 	}
 
-	private void addToCollection(Collection<MessageChannel> channels, Collection<?> channelKeys, Message<?> message) {
+	private void addToCollection(Collection<MessageChannel> channels, @Nullable Collection<?> channelKeys, Message<?> message) {
 		if (channelKeys == null) {
 			return;
 		}

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

@@ -21,6 +21,8 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
@@ -47,6 +49,7 @@
  * @author Stefan Ferstl
  * @author Artem Bilan
  * @author Christian Tzolov
+ * @author Glenn Renfro
  */
 @ManagedResource
 @IntegrationManagedResource
@@ -56,9 +59,9 @@ public abstract class AbstractMessageRouter extends AbstractMessageHandler imple
 
 	private final MessagingTemplate messagingTemplate = new MessagingTemplate();
 
-	private volatile MessageChannel defaultOutputChannel;
+	private volatile @Nullable MessageChannel defaultOutputChannel;
 
-	private volatile String defaultOutputChannelName;
+	private volatile @Nullable String defaultOutputChannelName;
 
 	private volatile boolean ignoreSendFailures;
 
@@ -85,7 +88,7 @@ public void setDefaultOutputChannel(MessageChannel defaultOutputChannel) {
 	 * @since 4.3
 	 */
 	@Override
-	public MessageChannel getDefaultOutputChannel() {
+	public @Nullable MessageChannel getDefaultOutputChannel() {
 		if (this.defaultOutputChannelName != null) {
 			this.lock.lock();
 			try {

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

@@ -16,6 +16,8 @@
 
 package org.springframework.integration.router;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.MessageChannel;
 
 /**
@@ -31,6 +33,7 @@ public interface MessageRouter {
 	 * Get the default output channel.
 	 * @return the channel.
 	 */
+	@Nullable
 	MessageChannel getDefaultOutputChannel();
 
 }

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

@@ -20,6 +20,8 @@
 import java.util.LinkedList;
 import java.util.List;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.messaging.Message;
 import org.springframework.util.CollectionUtils;
 
@@ -31,6 +33,7 @@
  * @author Oleg Zhurakousky
  * @author Gary Russell
  * @author Artem Bilan
+ * @author Glenn Renfro
  */
 public class PayloadTypeRouter extends AbstractMappingMessageRouter {
 
@@ -46,7 +49,7 @@ public class PayloadTypeRouter extends AbstractMappingMessageRouter {
 	 *    preferring direct interface over indirect subclass
 	 */
 	@Override
-	protected List<Object> getChannelKeys(Message<?> message) {
+	protected @Nullable List<Object> getChannelKeys(Message<?> message) {
 		if (CollectionUtils.isEmpty(getChannelMappings())) {
 			return null;
 		}
@@ -59,7 +62,7 @@ protected List<Object> getChannelKeys(Message<?> message) {
 		return (closestMatch != null) ? Collections.singletonList(closestMatch) : null;
 	}
 
-	private String findClosestMatch(Class<?> type, boolean isArray) { // NOSONAR
+	private @Nullable String findClosestMatch(Class<?> type, boolean isArray) { // NOSONAR
 		int minTypeDiffWeight = Integer.MAX_VALUE;
 		List<String> matches = new LinkedList<>();
 		for (String candidate : getChannelMappings().keySet()) {

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

@@ -76,6 +76,7 @@
  * @author Artem Bilan
  * @author Liujiong
  * @author Gary Russell
+ * @author Glenn Renfro
  */
 public class RecipientListRouter extends AbstractMessageRouter implements RecipientListRouterManagement {
 
@@ -151,11 +152,11 @@ public void addRecipient(String channelName) {
 		addRecipient(channelName, (MessageSelector) null);
 	}
 
-	public void addRecipient(String channelName, MessageSelector selector) {
+	public void addRecipient(String channelName, @Nullable MessageSelector selector) {
 		addRecipient(channelName, selector, this.recipients);
 	}
 
-	private void addRecipient(String channelName, MessageSelector selector, Queue<Recipient> recipientsToAdd) {
+	private void addRecipient(String channelName, @Nullable MessageSelector selector, Queue<Recipient> recipientsToAdd) {
 		Assert.hasText(channelName, "'channelName' must not be empty.");
 		Recipient recipient = new Recipient(channelName, selector);
 		setupRecipient(recipient);
@@ -166,7 +167,7 @@ public void addRecipient(MessageChannel channel) {
 		addRecipient(channel, null);
 	}
 
-	public void addRecipient(MessageChannel channel, MessageSelector selector) {
+	public void addRecipient(MessageChannel channel, @Nullable MessageSelector selector) {
 		Recipient recipient = new Recipient(channel, selector);
 		setupRecipient(recipient);
 		this.recipients.add(recipient);
@@ -273,19 +274,19 @@ protected void onInit() {
 
 	public static class Recipient {
 
-		private final MessageSelector selector;
+		private final @Nullable MessageSelector selector;
 
-		private MessageChannel channel;
+		private @Nullable MessageChannel channel;
 
-		private String channelName;
+		private @Nullable String channelName;
 
-		private DestinationResolver<MessageChannel> channelResolver;
+		private @Nullable DestinationResolver<MessageChannel> channelResolver;
 
 		public Recipient(MessageChannel channel) {
 			this(channel, null);
 		}
 
-		public Recipient(MessageChannel channel, MessageSelector selector) {
+		public Recipient(MessageChannel channel, @Nullable MessageSelector selector) {
 			this.channel = channel;
 			this.selector = selector;
 		}
@@ -294,7 +295,7 @@ public Recipient(String channelName) {
 			this(channelName, null);
 		}
 
-		public Recipient(String channelName, MessageSelector selector) {
+		public Recipient(String channelName, @Nullable MessageSelector selector) {
 			this.channelName = channelName;
 			this.selector = selector;
 		}
@@ -303,7 +304,7 @@ public void setChannelResolver(DestinationResolver<MessageChannel> channelResolv
 			this.channelResolver = channelResolver;
 		}
 
-		private MessageSelector getSelector() {
+		private @Nullable MessageSelector getSelector() {
 			return this.selector;
 		}
 

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

@@ -1,4 +1,5 @@
 /**
  * Provides classes supporting the router pattern.
  */
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.router;