Support DestinationVariable on RSocket handlers

Prior to this commit, the pattern destination variables were not set in
the message headers prior to calling the handler. In this case, the
`DestinationVariableMethodArgumentResolver` could not get the
destination variables from the message headers and resolve those as
handler arguments.

This commit mutates the message headers if the message destination
contains patterns.

Fixes gh-22776

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

@@ -24,9 +24,12 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.LinkedHashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.function.Predicate;
 
+import reactor.core.publisher.Mono;
+
 import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ConfigurableApplicationContext;
@@ -39,6 +42,7 @@ import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.CompositeMessageCondition;
 import org.springframework.messaging.handler.DestinationPatternsMessageCondition;
+import org.springframework.messaging.handler.HandlerMethod;
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.handler.annotation.support.AnnotationExceptionHandlerMethodResolver;
 import org.springframework.messaging.handler.invocation.AbstractExceptionHandlerMethodResolver;
@@ -46,9 +50,11 @@ import org.springframework.messaging.handler.invocation.reactive.AbstractEncoder
 import org.springframework.messaging.handler.invocation.reactive.AbstractMethodMessageHandler;
 import org.springframework.messaging.handler.invocation.reactive.HandlerMethodArgumentResolver;
 import org.springframework.messaging.handler.invocation.reactive.HandlerMethodReturnValueHandler;
+import org.springframework.messaging.support.MessageHeaderAccessor;
 import org.springframework.stereotype.Controller;
 import org.springframework.util.AntPathMatcher;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.PathMatcher;
 import org.springframework.util.StringValueResolver;
 import org.springframework.validation.Validator;
@@ -311,4 +317,19 @@ public class MessageMappingMessageHandler extends AbstractMethodMessageHandler<C
 		return new AnnotationExceptionHandlerMethodResolver(beanType);
 	}
 
+	@Override
+	protected Mono<Void> handleMatch(CompositeMessageCondition mapping, HandlerMethod handlerMethod, Message<?> message) {
+		Set<String> patterns = mapping.getCondition(DestinationPatternsMessageCondition.class).getPatterns();
+		if (!CollectionUtils.isEmpty(patterns)) {
+			String pattern = patterns.iterator().next();
+			String destination = getDestination(message);
+			Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(pattern, destination);
+			if (!CollectionUtils.isEmpty(vars)) {
+				MessageHeaderAccessor mha = MessageHeaderAccessor.getAccessor(message, MessageHeaderAccessor.class);
+				Assert.state(mha != null && mha.isMutable(), "Mutable MessageHeaderAccessor required");
+				mha.setHeader(DestinationVariableMethodArgumentResolver.DESTINATION_TEMPLATE_VARIABLES_HEADER, vars);
+			}
+		}
+		return super.handleMatch(mapping, handlerMethod, message);
+	}
 }

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

@@ -381,7 +381,11 @@ public abstract class AbstractMethodMessageHandler<T>
 			// handleNoMatch would have been invoked already
 			return Mono.empty();
 		}
-		HandlerMethod handlerMethod = match.getHandlerMethod().createWithResolvedBean();
+		return handleMatch(match.mapping, match.handlerMethod, message);
+	}
+
+	protected Mono<Void> handleMatch(T mapping, HandlerMethod handlerMethod, Message<?> message) {
+		handlerMethod = handlerMethod.createWithResolvedBean();
 		return this.invocableHelper.handleMessage(handlerMethod, message);
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/rsocket/MessagingRSocket.java

@@ -180,6 +180,7 @@ class MessagingRSocket extends AbstractRSocket {
 
 	private MessageHeaders createHeaders(String destination, @Nullable MonoProcessor<?> replyMono) {
 		MessageHeaderAccessor headers = new MessageHeaderAccessor();
+		headers.setLeaveMutable(true);
 		headers.setHeader(DestinationPatternsMessageCondition.LOOKUP_DESTINATION_HEADER, destination);
 		if (this.dataMimeType != null) {
 			headers.setContentType(this.dataMimeType);

spring-messaging/src/test/java/org/springframework/messaging/handler/annotation/support/reactive/MessageMappingMessageHandlerTests.java

@@ -39,10 +39,13 @@ import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.DestinationPatternsMessageCondition;
+import org.springframework.messaging.handler.annotation.DestinationVariable;
 import org.springframework.messaging.handler.annotation.MessageExceptionHandler;
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.handler.invocation.reactive.TestEncoderMethodReturnValueHandler;
 import org.springframework.messaging.support.GenericMessage;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.messaging.support.MessageHeaderAccessor;
 import org.springframework.stereotype.Controller;
 
 import static java.nio.charset.StandardCharsets.*;
@@ -89,6 +92,13 @@ public class MessageMappingMessageHandlerTests {
 		verifyOutputContent(Collections.singletonList("abcdef::response"));
 	}
 
+	@Test
+	public void handleWithDestinationVariable() {
+		MessageMappingMessageHandler messsageHandler = initMesssageHandler();
+		messsageHandler.handleMessage(message("destination.test", "abcdef")).block(Duration.ofSeconds(5));
+		verifyOutputContent(Collections.singletonList("test::abcdef::response"));
+	}
+
 	@Test
 	public void handleException() {
 		MessageMappingMessageHandler messsageHandler = initMesssageHandler();
@@ -143,9 +153,11 @@ public class MessageMappingMessageHandlerTests {
 	}
 
 	private Message<?> message(String destination, String... content) {
-		return new GenericMessage<>(
-				Flux.fromIterable(Arrays.asList(content)).map(payload -> toDataBuffer(payload)),
-				Collections.singletonMap(DestinationPatternsMessageCondition.LOOKUP_DESTINATION_HEADER, destination));
+		Flux<DataBuffer> payload = Flux.fromIterable(Arrays.asList(content)).map(parts -> toDataBuffer(parts));
+		MessageHeaderAccessor headers = new MessageHeaderAccessor();
+		headers.setLeaveMutable(true);
+		headers.setHeader(DestinationPatternsMessageCondition.LOOKUP_DESTINATION_HEADER, destination);
+		return MessageBuilder.createMessage(payload, headers.getMessageHeaders());
 	}
 
 	private DataBuffer toDataBuffer(String payload) {
@@ -181,6 +193,11 @@ public class MessageMappingMessageHandlerTests {
 			return payload + "::response";
 		}
 
+		@MessageMapping("destination.{variable}")
+		String handleWithDestinationVariable(@DestinationVariable String variable, String payload) {
+			return variable + "::" + payload + "::response";
+		}
+
 		@MessageMapping("exception")
 		String handleAndThrow() {
 			throw new IllegalArgumentException("rejected");