Simplify RSocket client responder config

Now that responder RSocketStrategies also exposes responder strategies,
AnnotationClientResponderConfigurer is reduced and no longer needs to
be public. This commit folds it into RSocketMessageHandler as a nested
class and exposes it as a ClientRSocketFactoryConfigurer through a
static method that accepts the handlers to use.

Effectively a shortcut for creating RSocketMessageHandler, giving it
RSocketStrategies, calling afterPropertiesSet, and then the instance
createResponder.

See gh-23314

Author: rstoyanchev

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

@@ -30,7 +30,7 @@
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.codec.Decoder;
 import org.springframework.lang.Nullable;
-import org.springframework.messaging.rsocket.annotation.support.AnnotationClientResponderConfigurer;
+import org.springframework.messaging.rsocket.annotation.support.RSocketMessageHandler;
 import org.springframework.util.MimeType;
 
 /**
@@ -165,14 +165,15 @@ interface Builder {
 
 		/**
 		 * Callback to configure the {@code ClientRSocketFactory} directly.
-		 * <p>See {@link AnnotationClientResponderConfigurer} for configuring a
-		 * client side responder.
+		 * <p>See static factory method
+		 * {@link RSocketMessageHandler#clientResponder(Object...)} for
+		 * configuring a client side responder with annotated methods.
 		 * <p><strong>Note:</strong> Do not set {@link #dataMimeType(MimeType)}
 		 * and {@link #metadataMimeType(MimeType)} directly on the
 		 * {@code ClientRSocketFactory}. Use the shortcuts on this builder
 		 * instead since the created {@code RSocketRequester} needs to be aware
 		 * of those settings.
-		 * @see AnnotationClientResponderConfigurer
+		 * @see RSocketMessageHandler#clientResponder(Object...)
 		 */
 		RSocketRequester.Builder rsocketFactory(ClientRSocketFactoryConfigurer configurer);
 

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

@@ -24,10 +24,12 @@
 
 import io.rsocket.ConnectionSetupPayload;
 import io.rsocket.RSocket;
+import io.rsocket.RSocketFactory;
 import io.rsocket.SocketAcceptor;
 import io.rsocket.frame.FrameType;
 import reactor.core.publisher.Mono;
 
+import org.springframework.beans.BeanUtils;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.core.codec.Decoder;
@@ -40,6 +42,7 @@
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.handler.annotation.reactive.MessageMappingMessageHandler;
 import org.springframework.messaging.handler.invocation.reactive.HandlerMethodReturnValueHandler;
+import org.springframework.messaging.rsocket.ClientRSocketFactoryConfigurer;
 import org.springframework.messaging.rsocket.DefaultMetadataExtractor;
 import org.springframework.messaging.rsocket.MetadataExtractor;
 import org.springframework.messaging.rsocket.RSocketRequester;
@@ -324,10 +327,50 @@ private MessagingRSocket createResponder(ConnectionSetupPayload setupPayload, RS
 		Assert.notNull(strategies, "No RSocketStrategies. Was afterPropertiesSet not called?");
 		RSocketRequester requester = RSocketRequester.wrap(rsocket, dataMimeType, metadataMimeType, strategies);
 
-		Assert.notNull(this.metadataExtractor, () -> "No MetadataExtractor. Was afterPropertiesSet not called?");
+		Assert.state(this.metadataExtractor != null,
+				() -> "No MetadataExtractor. Was afterPropertiesSet not called?");
+
+		Assert.state(getRouteMatcher() != null,
+				() -> "No RouteMatcher. Was afterPropertiesSet not called?");
 
 		return new MessagingRSocket(dataMimeType, metadataMimeType, this.metadataExtractor, requester,
 				this, getRouteMatcher(), strategies);
 	}
 
+
+	public static ClientRSocketFactoryConfigurer clientResponder(Object... handlers) {
+		return new ResponderConfigurer(handlers);
+	}
+
+
+	private static final class ResponderConfigurer implements ClientRSocketFactoryConfigurer {
+
+		private final List<Object> handlers = new ArrayList<>();
+
+		@Nullable
+		private RSocketStrategies strategies;
+
+
+		private ResponderConfigurer(Object... handlers) {
+			Assert.notEmpty(handlers, "No handlers");
+			for (Object obj : handlers) {
+				this.handlers.add(obj instanceof Class ? BeanUtils.instantiateClass((Class<?>) obj) : obj);
+			}
+		}
+
+		@Override
+		public void configureWithStrategies(RSocketStrategies strategies) {
+			this.strategies = strategies;
+		}
+
+		@Override
+		public void configure(RSocketFactory.ClientRSocketFactory factory) {
+			RSocketMessageHandler handler = new RSocketMessageHandler();
+			handler.setHandlers(this.handlers);
+			handler.setRSocketStrategies(this.strategies);
+			handler.afterPropertiesSet();
+			factory.acceptor(handler.clientResponder());
+		}
+	}
+
 }

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

@@ -39,7 +39,6 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.rsocket.annotation.ConnectMapping;
-import org.springframework.messaging.rsocket.annotation.support.AnnotationClientResponderConfigurer;
 import org.springframework.messaging.rsocket.annotation.support.RSocketMessageHandler;
 import org.springframework.stereotype.Controller;
 
@@ -111,7 +110,7 @@ private static void connectAndRunTest(String connectionRoute) {
 						factory.metadataMimeType("text/plain");
 						factory.setupPayload(ByteBufPayload.create("", connectionRoute));
 					})
-					.rsocketFactory(AnnotationClientResponderConfigurer.withHandlers(new ClientHandler()))
+					.rsocketFactory(RSocketMessageHandler.clientResponder(new ClientHandler()))
 					.rsocketStrategies(context.getBean(RSocketStrategies.class))
 					.connectTcp("localhost", server.address().getPort())
 					.block();