Refine null-safety in spring-messaging

See gh-32475

spring-messaging/src/main/java/org/springframework/messaging/MessageDeliveryException.java

@@ -16,6 +16,8 @@
 
 package org.springframework.messaging;
 
+import org.springframework.lang.Nullable;
+
 /**
  * Exception that indicates an error occurred during message delivery.
  *
@@ -37,11 +39,11 @@ public class MessageDeliveryException extends MessagingException {
 		super(undeliveredMessage, description);
 	}
 
-	public MessageDeliveryException(Message<?> message, Throwable cause) {
+	public MessageDeliveryException(Message<?> message, @Nullable Throwable cause) {
 		super(message, cause);
 	}
 
-	public MessageDeliveryException(Message<?> undeliveredMessage, String description, Throwable cause) {
+	public MessageDeliveryException(Message<?> undeliveredMessage, String description, @Nullable Throwable cause) {
 		super(undeliveredMessage, description, cause);
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/MessagingException.java

@@ -53,7 +53,7 @@ public class MessagingException extends NestedRuntimeException {
 		this.failedMessage = message;
 	}
 
-	public MessagingException(Message<?> message, Throwable cause) {
+	public MessagingException(Message<?> message, @Nullable Throwable cause) {
 		super(null, cause);
 		this.failedMessage = message;
 	}

spring-messaging/src/main/java/org/springframework/messaging/converter/MappingJackson2MessageConverter.java

@@ -200,7 +200,8 @@ public class MappingJackson2MessageConverter extends AbstractMessageConverter {
 		}
 
 		// Do not log warning for serializer not found (note: different message wording on Jackson 2.9)
-		boolean debugLevel = (cause instanceof JsonMappingException && cause.getMessage().startsWith("Cannot find"));
+		boolean debugLevel = (cause instanceof JsonMappingException && cause.getMessage() != null
+				&& cause.getMessage().startsWith("Cannot find"));
 
 		if (debugLevel ? logger.isDebugEnabled() : logger.isWarnEnabled()) {
 			String msg = "Failed to evaluate Jackson " + (type instanceof JavaType ? "de" : "") +

spring-messaging/src/main/java/org/springframework/messaging/handler/CompositeMessageCondition.java

@@ -80,6 +80,7 @@ public class CompositeMessageCondition implements MessageCondition<CompositeMess
 	}
 
 	@Override
+	@Nullable
 	public CompositeMessageCondition getMatchingCondition(Message<?> message) {
 		List<MessageCondition<?>> result = new ArrayList<>(this.messageConditions.size());
 		for (MessageCondition<?> condition : this.messageConditions) {

spring-messaging/src/main/java/org/springframework/messaging/handler/annotation/reactive/AbstractNamedValueMethodArgumentResolver.java

@@ -81,6 +81,7 @@ public abstract class AbstractNamedValueMethodArgumentResolver implements SyncHa
 
 
 	@Override
+	@Nullable
 	public Object resolveArgumentValue(MethodParameter parameter, Message<?> message) {
 		NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
 		MethodParameter nestedParameter = parameter.nestedIfOptional();

spring-messaging/src/main/java/org/springframework/messaging/handler/annotation/reactive/MessageMappingMessageHandler.java

@@ -272,6 +272,7 @@ public class MessageMappingMessageHandler extends AbstractMethodMessageHandler<C
 
 
 	@Override
+	@Nullable
 	protected CompositeMessageCondition getMappingForMethod(Method method, Class<?> handlerType) {
 		CompositeMessageCondition methodCondition = getCondition(method);
 		if (methodCondition != null) {
@@ -325,12 +326,14 @@ public class MessageMappingMessageHandler extends AbstractMethodMessageHandler<C
 	}
 
 	@Override
+	@Nullable
 	protected RouteMatcher.Route getDestination(Message<?> message) {
 		return (RouteMatcher.Route) message.getHeaders()
 				.get(DestinationPatternsMessageCondition.LOOKUP_DESTINATION_HEADER);
 	}
 
 	@Override
+	@Nullable
 	protected CompositeMessageCondition getMatchingMapping(CompositeMessageCondition mapping, Message<?> message) {
 		return mapping.getMatchingCondition(message);
 	}

spring-messaging/src/main/java/org/springframework/messaging/handler/annotation/support/AbstractNamedValueMethodArgumentResolver.java

@@ -89,6 +89,7 @@ public abstract class AbstractNamedValueMethodArgumentResolver implements Handle
 
 
 	@Override
+	@Nullable
 	public Object resolveArgument(MethodParameter parameter, Message<?> message) throws Exception {
 		NamedValueInfo namedValueInfo = getNamedValueInfo(parameter);
 		MethodParameter nestedParameter = parameter.nestedIfOptional();

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/InvocableHandlerMethod.java

@@ -111,7 +111,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 	 * @see #doInvoke
 	 */
 	@Nullable
-	public Object invoke(Message<?> message, Object... providedArgs) throws Exception {
+	public Object invoke(Message<?> message, @Nullable Object... providedArgs) throws Exception {
 		Object[] args = getMethodArgumentValues(message, providedArgs);
 		if (logger.isTraceEnabled()) {
 			logger.trace("Arguments: " + Arrays.toString(args));
@@ -125,7 +125,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 	 * <p>The resulting array will be passed into {@link #doInvoke}.
 	 * @since 5.1.2
 	 */
-	protected Object[] getMethodArgumentValues(Message<?> message, Object... providedArgs) throws Exception {
+	protected Object[] getMethodArgumentValues(Message<?> message, @Nullable Object... providedArgs) throws Exception {
 		MethodParameter[] parameters = getMethodParameters();
 		if (ObjectUtils.isEmpty(parameters)) {
 			return EMPTY_ARGS;

spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/ReactiveReturnValueHandler.java

@@ -23,6 +23,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
+import org.springframework.lang.Nullable;
 
 /**
  * Support for single-value reactive types (like {@code Mono} or {@code Single})
@@ -57,6 +58,7 @@ public class ReactiveReturnValueHandler extends AbstractAsyncReturnValueHandler
 	}
 
 	@Override
+	@Nullable
 	public CompletableFuture<?> toCompletableFuture(Object returnValue, MethodParameter returnType) {
 		ReactiveAdapter adapter = this.adapterRegistry.getAdapter(returnType.getParameterType(), returnValue);
 		if (adapter != null) {

spring-messaging/src/main/java/org/springframework/messaging/rsocket/annotation/support/RSocketFrameTypeMessageCondition.java

@@ -134,6 +134,7 @@ public class RSocketFrameTypeMessageCondition extends AbstractMessageCondition<R
 	}
 
 	@Override
+	@Nullable
 	public RSocketFrameTypeMessageCondition getMatchingCondition(Message<?> message) {
 		FrameType actual = message.getHeaders().get(FRAME_TYPE_HEADER, FrameType.class);
 		if (actual != null) {

spring-messaging/src/main/java/org/springframework/messaging/rsocket/service/RSocketServiceProxyFactory.java

@@ -247,6 +247,7 @@ public final class RSocketServiceProxyFactory {
 		}
 
 		@Override
+		@Nullable
 		public Object invoke(MethodInvocation invocation) throws Throwable {
 			Method method = invocation.getMethod();
 			RSocketServiceMethod serviceMethod = this.serviceMethods.get(method);

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/PrincipalMethodArgumentResolver.java

@@ -20,6 +20,7 @@ import java.security.Principal;
 import java.util.Optional;
 
 import org.springframework.core.MethodParameter;
+import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
@@ -40,6 +41,7 @@ public class PrincipalMethodArgumentResolver implements HandlerMethodArgumentRes
 	}
 
 	@Override
+	@Nullable
 	public Object resolveArgument(MethodParameter parameter, Message<?> message){
 		Principal user = SimpMessageHeaderAccessor.getUser(message.getHeaders());
 		return parameter.isOptional() ? Optional.ofNullable(user) : user;

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandler.java

@@ -476,6 +476,7 @@ public class SimpAnnotationMethodMessageHandler extends AbstractMethodMessageHan
 	}
 
 	@Override
+	@Nullable
 	protected String getLookupDestination(@Nullable String destination) {
 		if (destination == null) {
 			return null;