GH-3207: RSocket inbound: decode each flux item (#3208)

* GH-3207: RSocket inbound: decode each flux item

Fixes #3207

Previously an incoming RSocket Publisher has been decoded as a single unit
leading to extra work on the client side, e.g. a delimiter has to be provided
to treat each payload item as independent

* To have a consistency with Spring Messaging and its `PayloadMethodArgumentResolver`
change an `RSocketInboundGateway` to process inbound payloads as `Flux` and decode
each item independently.
* Change `RSocketDslTests` to remove delimiters and make it consistent with the regular
`RSocketRequester` client

* * Add `decodeFluxAsUnit` option into `RSocketInboundGateway`
* Document the change

Author: artembilan

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,6 @@ public class RSocketInboundGatewayParser extends AbstractInboundGatewayParser {
 
 	private static final List<String> NON_ELIGIBLE_ATTRIBUTES =
 			Arrays.asList("path",
-					"interaction-models",
 					"rsocket-strategies",
 					"rsocket-connector",
 					"request-element-type");
@@ -61,7 +60,6 @@ protected void doPostProcess(BeanDefinitionBuilder builder, Element element) {
 				"rSocketStrategies");
 		IntegrationNamespaceUtils.setReferenceIfAttributeDefined(builder, element, "rsocket-connector",
 				"RSocketConnector");
-		IntegrationNamespaceUtils.setValueIfAttributeDefined(builder, element, "interaction-models");
 	}
 
 }

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

@@ -23,6 +23,8 @@
 import org.springframework.integration.rsocket.inbound.RSocketInboundGateway;
 import org.springframework.messaging.rsocket.RSocketStrategies;
 
+import reactor.core.publisher.Flux;
+
 /**
  * The {@link MessagingGatewaySpec} implementation for the {@link RSocketInboundGateway}.
  *
@@ -82,4 +84,16 @@ public RSocketInboundGatewaySpec requestElementType(ResolvableType requestElemen
 		return this;
 	}
 
+	/**
+	 * Configure an option to decode an incoming {@link Flux} as a single unit or each its event separately.
+	 * @param decodeFluxAsUnit decode incoming {@link Flux} as a single unit or each event separately.
+	 * @return the spec
+	 * @since 5.3
+	 * @see RSocketInboundGateway#setDecodeFluxAsUnit(boolean)
+	 */
+	public RSocketInboundGatewaySpec decodeFluxAsUnit(boolean decodeFluxAsUnit) {
+		this.target.setDecodeFluxAsUnit(decodeFluxAsUnit);
+		return this;
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -85,6 +85,8 @@ public class RSocketInboundGateway extends MessagingGatewaySupport implements In
 	@Nullable
 	private ResolvableType requestElementType;
 
+	private boolean decodeFluxAsUnit;
+
 	/**
 	 * Instantiate based on the provided path patterns to map this endpoint for incoming RSocket requests.
 	 * @param pathArg the mapping patterns to use.
@@ -160,6 +162,20 @@ public void setRequestElementType(ResolvableType requestElementType) {
 		this.requestElementType = requestElementType;
 	}
 
+	/**
+	 * Configure an option to decode an incoming {@link Flux} as a single unit or each its event separately.
+	 * Defaults to {@code false} for consistency with Spring Messaging {@code @MessageMapping}.
+	 * The target {@link Flux} decoding logic depends on the {@link Decoder} selected.
+	 * For example a {@link org.springframework.core.codec.StringDecoder} requires a new line separator to
+	 * be present in the stream to indicate a byte buffer end.
+	 * @param decodeFluxAsUnit decode incoming {@link Flux} as a single unit or each event separately.
+	 * @since 5.3
+	 * @see Decoder#decode(Publisher, ResolvableType, MimeType, java.util.Map)
+	 */
+	public void setDecodeFluxAsUnit(boolean decodeFluxAsUnit) {
+		this.decodeFluxAsUnit = decodeFluxAsUnit;
+	}
+
 	@Override
 	protected void onInit() {
 		super.onInit();
@@ -219,14 +235,17 @@ private Mono<Message<?>> decodeRequestMessage(Message<?> requestMessage) {
 	@SuppressWarnings("unchecked")
 	@Nullable
 	private Object decodePayload(Message<?> requestMessage) {
-		ResolvableType elementType = this.requestElementType;
+		ResolvableType elementType;
 		MimeType mimeType = requestMessage.getHeaders().get(MessageHeaders.CONTENT_TYPE, MimeType.class);
-		if (elementType == null) {
+		if (this.requestElementType == null) {
 			elementType =
 					mimeType != null && "text".equals(mimeType.getType())
 							? ResolvableType.forClass(String.class)
 							: ResolvableType.forClass(byte[].class);
 		}
+		else {
+			elementType = this.requestElementType;
+		}
 
 		Object payload = requestMessage.getPayload();
 
@@ -235,9 +254,18 @@ private Object decodePayload(Message<?> requestMessage) {
 		if (payload instanceof DataBuffer) {
 			return decoder.decode((DataBuffer) payload, elementType, mimeType, null);
 		}
-		else {
+		else if (this.decodeFluxAsUnit) {
 			return decoder.decode((Publisher<DataBuffer>) payload, elementType, mimeType, null);
 		}
+		else {
+			return Flux.from((Publisher<DataBuffer>) payload)
+					.handle((buffer, synchronousSink) -> {
+						Object value = decoder.decode(buffer, elementType, mimeType, null);
+						if (value != null) {
+							synchronousSink.next(value);
+						}
+					});
+		}
 	}
 
 	private Flux<DataBuffer> createReply(Object reply, Message<?> requestMessage) {

spring-integration-rsocket/src/main/resources/org/springframework/integration/rsocket/config/spring-integration-rsocket.xsd

@@ -93,6 +93,16 @@
 							</xsd:documentation>
 						</xsd:annotation>
 					</xsd:attribute>
+					<xsd:attribute name="decode-flux-as-unit" default="false">
+						<xsd:annotation>
+							<xsd:documentation>
+								Decode incoming Flux as a single unit or each event separately.
+							</xsd:documentation>
+						</xsd:annotation>
+						<xsd:simpleType>
+							<xsd:union memberTypes="xsd:boolean xsd:string"/>
+						</xsd:simpleType>
+					</xsd:attribute>
 				</xsd:extension>
 			</xsd:complexContent>
 		</xsd:complexType>

spring-integration-rsocket/src/test/java/org/springframework/integration/rsocket/config/RSocketInboundGatewayParserTests-context.xml

@@ -25,6 +25,7 @@
 								 auto-startup="false"
 								 request-channel="requestChannel"
 								 rsocket-strategies="rsocketStrategies"
-								 request-element-type="byte[]"/>
+								 request-element-type="byte[]"
+								 decode-flux-as-unit="true"/>
 
 </beans>

spring-integration-rsocket/src/test/java/org/springframework/integration/rsocket/config/RSocketInboundGatewayParserTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2019 the original author or authors.
+ * Copyright 2019-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -44,7 +44,7 @@ class RSocketInboundGatewayParserTests {
 	private RSocketInboundGateway inboundGateway;
 
 	@Test
-	void testOutboundGatewayParser() {
+	void testInboundGatewayParser() {
 		assertThat(TestUtils.getPropertyValue(this.inboundGateway, "rsocketConnector"))
 				.isSameAs(this.clientRSocketConnector);
 		assertThat(TestUtils.getPropertyValue(this.inboundGateway, "rsocketStrategies"))
@@ -54,6 +54,7 @@ void testOutboundGatewayParser() {
 				.isEqualTo(byte[].class);
 		assertThat(this.inboundGateway.getInteractionModels())
 				.containsExactly(RSocketInteractionModel.fireAndForget, RSocketInteractionModel.requestChannel);
+		assertThat(TestUtils.getPropertyValue(this.inboundGateway, "decodeFluxAsUnit", Boolean.class)).isTrue();
 	}
 
 }

spring-integration-rsocket/src/test/java/org/springframework/integration/rsocket/dsl/RSocketDslTests.java

@@ -31,6 +31,8 @@
 import org.springframework.integration.rsocket.ClientRSocketConnector;
 import org.springframework.integration.rsocket.RSocketInteractionModel;
 import org.springframework.integration.rsocket.ServerRSocketConnector;
+import org.springframework.integration.support.MessageBuilder;
+import org.springframework.messaging.Message;
 import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 
@@ -48,17 +50,30 @@ public class RSocketDslTests {
 
 	@Autowired
 	@Qualifier("rsocketUpperCaseRequestFlow.gateway")
-	private Function<Flux<String>, Flux<String>> rsocketUpperCaseFlowFunction;
+	private Function<Object, Flux<String>> rsocketUpperCaseFlowFunction;
 
 	@Test
 	void testRsocketUpperCaseFlows() {
-		Flux<String> result = this.rsocketUpperCaseFlowFunction.apply(Flux.just("a\n", "b\n", "c\n"));
+		Flux<String> result = this.rsocketUpperCaseFlowFunction.apply(Flux.just("a", "b", "c"));
 
 		StepVerifier.create(result)
 				.expectNext("A", "B", "C")
 				.verifyComplete();
 	}
 
+	@Test
+	void testRsocketUpperCaseWholeFlows() {
+		Message<Flux<String>> testMessage =
+				MessageBuilder.withPayload(Flux.just("a", "b", "c", "\n"))
+						.setHeader("route", "/uppercaseWhole")
+						.build();
+		Flux<String> result = this.rsocketUpperCaseFlowFunction.apply(testMessage);
+
+		StepVerifier.create(result)
+				.expectNext("ABC")
+				.verifyComplete();
+	}
+
 	@Configuration
 	@EnableIntegration
 	public static class TestConfiguration {
@@ -80,7 +95,8 @@ public ClientRSocketConnector clientRSocketConnector(ServerRSocketConnector serv
 		public IntegrationFlow rsocketUpperCaseRequestFlow(ClientRSocketConnector clientRSocketConnector) {
 			return IntegrationFlows
 					.from(Function.class)
-					.handle(RSockets.outboundGateway("/uppercase")
+					.handle(RSockets.outboundGateway(message ->
+							message.getHeaders().getOrDefault("route", "/uppercase"))
 									.interactionModel((message) -> RSocketInteractionModel.requestChannel)
 									.expectedResponseType("T(java.lang.String)")
 									.clientRSocketConnector(clientRSocketConnector),
@@ -100,6 +116,16 @@ public IntegrationFlow rsocketUpperCaseFlow() {
 					.get();
 		}
 
+		@Bean
+		public IntegrationFlow rsocketUpperCaseWholeFlow() {
+			return IntegrationFlows
+					.from(RSockets.inboundGateway("/uppercaseWhole")
+							.interactionModels(RSocketInteractionModel.requestChannel)
+							.decodeFluxAsUnit(true))
+					.<Flux<String>, Flux<String>>transform((flux) -> flux.map(String::toUpperCase))
+					.get();
+		}
+
 	}
 
 }

src/reference/asciidoc/rsocket.adoc

@@ -137,6 +137,12 @@ The `payload` of the message to send downstream is always a `Flux` according to
 When in a `fireAndForget` RSocket interaction model, the message has a plain converted `payload`.
 The reply `payload` could be a plain object or a `Publisher` - the `RSocketInboundGateway` converts both of them properly into an RSocket response according to the encoders provided in the `RSocketStrategies`.
 
+Starting with version 5.3, a `decodeFluxAsUnit` option (default `false`) is added to the `RSocketInboundGateway`.
+By default incoming `Flux` is transformed the way that each its event is decoded separately.
+This is an exact behavior present currently with `@MessageMapping` semantics.
+To restore a previous behavior or decode the whole `Flux` as single unit according application requirements, the `decodeFluxAsUnit` has to be set to `true`.
+However the target decoding logic depends on the `Decoder` selected, e.g. a `StringDecoder` requires a new line separator (by default) to be present in the stream to indicate a byte buffer end.
+
 See <<rsocket-java-config>> for samples how to configure an `RSocketInboundGateway` endpoint and deal with payloads downstream.
 
 [[rsocket-outbound]]

src/reference/asciidoc/whats-new.adoc

@@ -98,3 +98,9 @@ See <<./ws.adoc#ws,Web Services Support>> for more information.
 
 The `FailoverClientConnectionFactory` no longer fails back, by default, until the current connection fails.
 See <<./ip.adoc#failover-cf,TCP Failover Client Connection Factory>> for more information.
+
+[[x5.3-rsocket]]
+=== RSocket Changes
+
+A `decodeFluxAsUnit` option has been added to the `RSocketInboundGateway` with the meaning to decode incoming `Flux` as a single unit or apply decoding for each event in it.
+See <<./rsocket.adoc#rsocket-inbound,RSocket Inbound Gateway>> for more information.