GH-10083: Apply NullAbility to rsocket module

Related to: #10083

* Remove `@Nullable`
* Revert `@Nullable` in `RSocketOutboundGateway#RSocketRequester`
* Change to private ctor

Signed-off-by: Tran Ngoc Nhan <ngocnhan.tran1996@gmail.com>

Author: ngocnhan-tran1996

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/AbstractRSocketConnector.java

@@ -16,14 +16,15 @@
 
 package org.springframework.integration.rsocket;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.SmartInitializingSingleton;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.SmartLifecycle;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.rsocket.RSocketStrategies;
 import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
@@ -64,8 +65,7 @@ public void setDataMimeType(@Nullable MimeType dataMimeType) {
 		this.rSocketMessageHandler.setDefaultDataMimeType(dataMimeType);
 	}
 
-	@Nullable
-	protected MimeType getDataMimeType() {
+	protected @Nullable MimeType getDataMimeType() {
 		return this.rSocketMessageHandler.getDefaultDataMimeType();
 	}
 

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/ClientRSocketConnector.java

@@ -49,14 +49,17 @@ public class ClientRSocketConnector extends AbstractRSocketConnector {
 	private RSocketConnectorConfigurer connectorConfigurer = (connector) -> {
 	};
 
+	@SuppressWarnings("NullAway.Init")
 	private Object setupData;
 
+	@SuppressWarnings("NullAway.Init")
 	private String setupRoute;
 
 	private Object[] setupRouteVars = new Object[0];
 
 	private boolean autoConnect;
 
+	@SuppressWarnings("NullAway.Init")
 	private RSocketRequester rsocketRequester;
 
 	/**

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/IntegrationRSocketMessageHandler.java

@@ -26,14 +26,14 @@
 
 import io.rsocket.Payload;
 import io.rsocket.frame.FrameType;
+import org.jspecify.annotations.Nullable;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.context.ApplicationContext;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.codec.Encoder;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.ReactiveMessageHandler;
 import org.springframework.messaging.handler.CompositeMessageCondition;
@@ -60,6 +60,7 @@
  */
 class IntegrationRSocketMessageHandler extends RSocketMessageHandler {
 
+	@SuppressWarnings("NullAway") // Reflection
 	private static final Method HANDLE_MESSAGE_METHOD =
 			ReflectionUtils.findMethod(ReactiveMessageHandler.class, "handleMessage", Message.class);
 
@@ -105,7 +106,7 @@ public void addEndpoint(IntegrationRSocketEndpoint endpoint) {
 		registerHandlerMethod(endpoint, HANDLE_MESSAGE_METHOD,
 				new CompositeMessageCondition(
 						frameTypeMessageCondition,
-						new DestinationPatternsMessageCondition(endpoint.getPath(), getRouteMatcher()))); // NOSONAR
+						new DestinationPatternsMessageCondition(endpoint.getPath(), obtainRouteMatcher()))); // NOSONAR
 	}
 
 	@Override
@@ -173,9 +174,8 @@ public Mono<Void> handleReturnValue(@Nullable Object returnValue, MethodParamete
 			}
 		}
 
-		@Nullable
 		@SuppressWarnings("unchecked")
-		private static AtomicReference<Flux<Payload>> getResponseReference(Message<?> message) {
+		private static @Nullable AtomicReference<Flux<Payload>> getResponseReference(Message<?> message) {
 			Object headerValue = message.getHeaders().get(RESPONSE_HEADER);
 			Assert.state(headerValue == null || headerValue instanceof AtomicReference, "Expected AtomicReference");
 			return (AtomicReference<Flux<Payload>>) headerValue;

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/ServerRSocketConnector.java

@@ -25,6 +25,7 @@
 import io.rsocket.transport.netty.server.CloseableChannel;
 import io.rsocket.transport.netty.server.TcpServerTransport;
 import io.rsocket.transport.netty.server.WebsocketServerTransport;
+import org.jspecify.annotations.Nullable;
 import reactor.core.Disposable;
 import reactor.core.publisher.Mono;
 import reactor.netty.http.server.HttpServer;
@@ -34,7 +35,6 @@
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
 import org.springframework.core.io.buffer.DataBuffer;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.rsocket.RSocketRequester;
 import org.springframework.messaging.rsocket.RSocketStrategies;
 import org.springframework.util.Assert;
@@ -51,11 +51,12 @@
  */
 public class ServerRSocketConnector extends AbstractRSocketConnector implements ApplicationEventPublisherAware {
 
-	private final ServerTransport<CloseableChannel> serverTransport;
+	private final @Nullable ServerTransport<CloseableChannel> serverTransport;
 
 	private Consumer<RSocketServer> serverConfigurer = (rsocketServer) -> {
 	};
 
+	@SuppressWarnings("NullAway.Init")
 	private Mono<CloseableChannel> serverMono;
 
 	/**
@@ -191,8 +192,7 @@ public Map<Object, RSocketRequester> getClientRSocketRequesters() {
 	 * @return the {@link RSocketRequester} or null.
 	 * @see ServerRSocketMessageHandler#getClientRSocketRequester(Object)
 	 */
-	@Nullable
-	public RSocketRequester getClientRSocketRequester(Object key) {
+	public @Nullable RSocketRequester getClientRSocketRequester(Object key) {
 		return serverRSocketMessageHandler().getClientRSocketRequester(key);
 	}
 

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/ServerRSocketMessageHandler.java

@@ -23,11 +23,12 @@
 import java.util.Map;
 import java.util.function.BiFunction;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.aot.hint.annotation.Reflective;
 import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.context.ApplicationEventPublisherAware;
 import org.springframework.core.io.buffer.DataBuffer;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.handler.CompositeMessageCondition;
@@ -60,6 +61,7 @@
 public class ServerRSocketMessageHandler extends IntegrationRSocketMessageHandler
 		implements ApplicationEventPublisherAware {
 
+	@SuppressWarnings("NullAway") // Reflection
 	private static final Method HANDLE_CONNECTION_SETUP_METHOD =
 			ReflectionUtils.findMethod(ServerRSocketMessageHandler.class, "handleConnectionSetup", Message.class);
 
@@ -68,7 +70,7 @@ public class ServerRSocketMessageHandler extends IntegrationRSocketMessageHandle
 	private BiFunction<Map<String, Object>, DataBuffer, Object> clientRSocketKeyStrategy =
 			(headers, data) -> data.toString(StandardCharsets.UTF_8);
 
-	private ApplicationEventPublisher applicationEventPublisher;
+	private @Nullable ApplicationEventPublisher applicationEventPublisher;
 
 	/**
 	 * Create an service side RSocket message handler instance for delegating
@@ -120,8 +122,7 @@ public Map<Object, RSocketRequester> getClientRSocketRequesters() {
 	 * @param key the key for mapped {@link RSocketRequester} if any.
 	 * @return the mapped {@link RSocketRequester} or null.
 	 */
-	@Nullable
-	public RSocketRequester getClientRSocketRequester(Object key) {
+	public @Nullable RSocketRequester getClientRSocketRequester(Object key) {
 		return this.clientRSocketRequesters.get(key);
 	}
 
@@ -146,6 +147,7 @@ private void handleConnectionSetup(Message<DataBuffer> connectMessage) {
 		RSocketRequester rsocketRequester =
 				messageHeaders.get(RSocketRequesterMethodArgumentResolver.RSOCKET_REQUESTER_HEADER,
 						RSocketRequester.class);
+		Assert.notNull(rsocketRequester, "'rsocketRequester' can not be null");
 		this.clientRSocketRequesters.put(rsocketRequesterKey, rsocketRequester);
 		RSocketConnectedEvent rSocketConnectedEvent =
 				new RSocketConnectedEvent(this, messageHeaders, dataBuffer, rsocketRequester); // NOSONAR

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/config/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Provides classes for RSocket XML namespace parsing and configuration support.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.rsocket.config;

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/dsl/package-info.java

@@ -1,6 +1,5 @@
 /**
  * Provides RSocket Components support for Spring Integration Java DSL.
  */
-@org.springframework.lang.NonNullApi
-@org.springframework.lang.NonNullFields
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.rsocket.dsl;

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/inbound/RSocketInboundGateway.java

@@ -19,6 +19,7 @@
 import java.util.Arrays;
 import java.util.concurrent.atomic.AtomicReference;
 
+import org.jspecify.annotations.Nullable;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
@@ -37,7 +38,6 @@
 import org.springframework.integration.rsocket.IntegrationRSocketEndpoint;
 import org.springframework.integration.rsocket.RSocketInteractionModel;
 import org.springframework.integration.support.MessageBuilder;
-import org.springframework.lang.Nullable;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageDeliveryException;
 import org.springframework.messaging.MessageHeaders;
@@ -78,11 +78,9 @@ public class RSocketInboundGateway extends MessagingGatewaySupport implements In
 
 	private RSocketStrategies rsocketStrategies = RSocketStrategies.create();
 
-	@Nullable
-	private AbstractRSocketConnector rsocketConnector;
+	private @Nullable AbstractRSocketConnector rsocketConnector;
 
-	@Nullable
-	private ResolvableType requestElementType;
+	private @Nullable ResolvableType requestElementType;
 
 	private boolean decodeFluxAsUnit;
 
@@ -188,8 +186,8 @@ protected void onInit() {
 	@Override
 	protected void doStart() {
 		super.doStart();
-		if (this.rsocketConnector instanceof ClientRSocketConnector) {
-			((ClientRSocketConnector) this.rsocketConnector).connect();
+		if (this.rsocketConnector instanceof ClientRSocketConnector clientRSocketConnector) {
+			clientRSocketConnector.connect();
 		}
 	}
 
@@ -265,8 +263,8 @@ private Object decodePayload(Message<?> requestMessage) {
 
 		// The MessagingRSocket logic ensures that we can have only a single DataBuffer payload or Flux<DataBuffer>.
 		Decoder<Object> decoder = this.rsocketStrategies.decoder(elementType, mimeType);
-		if (payload instanceof DataBuffer) {
-			return decoder.decode((DataBuffer) payload, elementType, mimeType, null);
+		if (payload instanceof DataBuffer dataBuffer) {
+			return decoder.decode(dataBuffer, elementType, mimeType, null);
 		}
 		else if (this.decodeFluxAsUnit) {
 			return decoder.decode((Publisher<DataBuffer>) payload, elementType, mimeType, null);

spring-integration-rsocket/src/main/java/org/springframework/integration/rsocket/inbound/package-info.java

@@ -1,5 +1,5 @@
 /**
  * Provides classes representing inbound RSocket components.
  */
-@org.springframework.lang.NonNullApi
+@org.jspecify.annotations.NullMarked
 package org.springframework.integration.rsocket.inbound;