Introduce ServerHttpMessageWriter/Reader to resolve hints

Issue: SPR-14693

Author: sdeleuze

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/method/annotation/AbstractMessageReaderArgumentResolver.java

@@ -18,6 +18,7 @@
 import java.lang.annotation.Annotation;
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
@@ -32,6 +33,7 @@
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.HttpMessageReader;
+import org.springframework.http.codec.ServerHttpMessageReader;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
@@ -115,8 +117,8 @@ public ReactiveAdapterRegistry getAdapterRegistry() {
 	protected Mono<Object> readBody(MethodParameter bodyParameter, boolean isBodyRequired,
 			ServerWebExchange exchange) {
 
-		Class<?> bodyType = ResolvableType.forMethodParameter(bodyParameter).resolve();
-		ReactiveAdapter adapter = getAdapterRegistry().getAdapterTo(bodyType);
+		ResolvableType bodyType = ResolvableType.forMethodParameter(bodyParameter);
+		ReactiveAdapter adapter = getAdapterRegistry().getAdapterTo(bodyType.resolve());
 
 		ResolvableType elementType = ResolvableType.forMethodParameter(bodyParameter);
 		if (adapter != null) {
@@ -130,9 +132,15 @@ protected Mono<Object> readBody(MethodParameter bodyParameter, boolean isBodyReq
 		}
 
 		for (HttpMessageReader<?> reader : getMessageReaders()) {
-			if (reader.canRead(elementType, mediaType, Collections.emptyMap())) {
+
+			Map<String, Object> hints = (reader instanceof ServerHttpMessageReader ?
+						((ServerHttpMessageReader<?>)reader).resolveReadHints(bodyType, elementType,
+								mediaType, exchange.getRequest()) : Collections.emptyMap());
+
+			if (reader.canRead(elementType, mediaType, hints)) {
+
 				if (adapter != null && adapter.getDescriptor().isMultiValue()) {
-					Flux<?> flux = reader.read(elementType, request, Collections.emptyMap())
+					Flux<?> flux = reader.read(elementType, request, hints)
 							.onErrorResumeWith(ex -> Flux.error(getReadError(ex, bodyParameter)));
 					if (checkRequired(adapter, isBodyRequired)) {
 						flux = flux.switchIfEmpty(Flux.error(getRequiredBodyError(bodyParameter)));
@@ -143,7 +151,7 @@ protected Mono<Object> readBody(MethodParameter bodyParameter, boolean isBodyReq
 					return Mono.just(adapter.fromPublisher(flux));
 				}
 				else {
-					Mono<?> mono = reader.readMono(elementType, request, Collections.emptyMap())
+					Mono<?> mono = reader.readMono(elementType, request, hints)
 							.otherwise(ex -> Mono.error(getReadError(ex, bodyParameter)));
 					if (checkRequired(adapter, isBodyRequired)) {
 						mono = mono.otherwiseIfEmpty(Mono.error(getRequiredBodyError(bodyParameter)));

spring-web-reactive/src/main/java/org/springframework/web/reactive/result/method/annotation/AbstractMessageWriterResultHandler.java

@@ -17,6 +17,7 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.stream.Collectors;
 
 import org.reactivestreams.Publisher;
@@ -28,6 +29,7 @@
 import org.springframework.core.ResolvableType;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.HttpMessageWriter;
+import org.springframework.http.codec.ServerHttpMessageWriter;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
@@ -89,22 +91,22 @@ public List<HttpMessageWriter<?>> getMessageWriters() {
 
 
 	@SuppressWarnings("unchecked")
-	protected Mono<Void> writeBody(Object body, MethodParameter bodyType, ServerWebExchange exchange) {
+	protected Mono<Void> writeBody(Object body, MethodParameter bodyParameter, ServerWebExchange exchange) {
 
-		Class<?> bodyClass = bodyType.getParameterType();
-		ReactiveAdapter adapter = getAdapterRegistry().getAdapterFrom(bodyClass, body);
+		ResolvableType bodyType = ResolvableType.forMethodParameter(bodyParameter);
+		ReactiveAdapter adapter = getAdapterRegistry().getAdapterFrom(bodyType.resolve(), body);
 
 		Publisher<?> publisher;
 		ResolvableType elementType;
 		if (adapter != null) {
 			publisher = adapter.toPublisher(body);
 			elementType = adapter.getDescriptor().isNoValue() ?
 					ResolvableType.forClass(Void.class) :
-					ResolvableType.forMethodParameter(bodyType).getGeneric(0);
+					bodyType.getGeneric(0);
 		}
 		else {
 			publisher = Mono.justOrEmpty(body);
-			elementType = ResolvableType.forMethodParameter(bodyType);
+			elementType = bodyType;
 		}
 
 		if (void.class == elementType.getRawClass() || Void.class == elementType.getRawClass()) {
@@ -121,10 +123,14 @@ protected Mono<Void> writeBody(Object body, MethodParameter bodyType, ServerWebE
 
 		if (bestMediaType != null) {
 			for (HttpMessageWriter<?> messageWriter : getMessageWriters()) {
-				if (messageWriter.canWrite(elementType, bestMediaType, Collections.emptyMap())) {
+				Map<String, Object> hints = (messageWriter instanceof ServerHttpMessageWriter ?
+						((ServerHttpMessageWriter<?>)messageWriter).resolveWriteHints(bodyType, elementType,
+								bestMediaType, exchange.getRequest()) : Collections.emptyMap());
+				if (messageWriter.canWrite(elementType, bestMediaType, hints)) {
+
 					ServerHttpResponse response = exchange.getResponse();
 					return messageWriter.write((Publisher) publisher, elementType,
-							bestMediaType, response, Collections.emptyMap());
+							bestMediaType, response, hints);
 				}
 			}
 		}

spring-web/src/main/java/org/springframework/http/codec/AbstractServerHttpMessageReader.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.http.codec;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
+import org.springframework.http.MediaType;
+import org.springframework.http.ReactiveHttpInputMessage;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+
+/**
+ * {@link HttpMessageReader} wrapper to extend that implements {@link ServerHttpMessageReader} in order
+ * to allow providing hints.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+public abstract class AbstractServerHttpMessageReader<T> implements ServerHttpMessageReader<T> {
+
+	private HttpMessageReader<T> reader;
+
+
+	public AbstractServerHttpMessageReader(HttpMessageReader<T> reader) {
+		this.reader = reader;
+	}
+
+	@Override
+	public boolean canRead(ResolvableType elementType, MediaType mediaType, Map<String, Object> hints) {
+		return this.reader.canRead(elementType, mediaType, hints);
+	}
+
+	@Override
+	public Flux<T> read(ResolvableType elementType, ReactiveHttpInputMessage inputMessage, Map<String, Object> hints) {
+		return this.reader.read(elementType, inputMessage, hints);
+	}
+
+	@Override
+	public Mono<T> readMono(ResolvableType elementType, ReactiveHttpInputMessage inputMessage, Map<String, Object> hints) {
+		return this.reader.readMono(elementType, inputMessage, hints);
+	}
+
+	@Override
+	public List<MediaType> getReadableMediaTypes() {
+		return this.reader.getReadableMediaTypes();
+	}
+
+	@Override
+	public final Map<String, Object> resolveReadHints(ResolvableType streamType,
+			ResolvableType elementType, MediaType mediaType, ServerHttpRequest request) {
+
+		Map<String, Object> hints = new HashMap<>();
+		if (this.reader instanceof ServerHttpMessageReader) {
+			hints.putAll(((ServerHttpMessageReader<T>)this.reader).resolveReadHints(streamType, elementType, mediaType, request));
+		}
+		hints.putAll(resolveReadHintsInternal(streamType, elementType, mediaType, request));
+		return hints;
+	}
+
+	/**
+	 * Abstract method that returns hints which can be used to customize how the body should be read.
+	 * Invoked from {@link #resolveReadHints}.
+	 * @param streamType the original type used in the method parameter. For annotation
+	 * based controllers, the {@link MethodParameter} is available via {@link ResolvableType#getSource()}.
+	 * @param elementType the stream element type to return
+	 * @param mediaType the media type to read, can be {@code null} if not specified.
+	 * Typically the value of a {@code Content-Type} header.
+	 * @param request the current HTTP request
+	 * @return Additional information about how to read the body
+	 */
+	protected abstract Map<String, Object> resolveReadHintsInternal(ResolvableType streamType,
+			ResolvableType elementType, MediaType mediaType, ServerHttpRequest request);
+
+}

spring-web/src/main/java/org/springframework/http/codec/AbstractServerHttpMessageWriter.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.http.codec;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.reactivestreams.Publisher;
+import reactor.core.publisher.Mono;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
+import org.springframework.http.MediaType;
+import org.springframework.http.ReactiveHttpOutputMessage;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+
+/**
+ * {@link HttpMessageWriter} wrapper to extend that implements {@link ServerHttpMessageWriter} in order
+ * to allow providing hints.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+public abstract class AbstractServerHttpMessageWriter<T> implements ServerHttpMessageWriter<T> {
+
+	private HttpMessageWriter<T> writer;
+
+
+	public AbstractServerHttpMessageWriter(HttpMessageWriter<T> writer) {
+		this.writer = writer;
+	}
+
+	@Override
+	public boolean canWrite(ResolvableType elementType, MediaType mediaType, Map<String, Object> hints) {
+		return this.writer.canWrite(elementType, mediaType, hints);
+	}
+
+	@Override
+	public Mono<Void> write(Publisher<? extends T> inputStream, ResolvableType elementType,
+			MediaType mediaType, ReactiveHttpOutputMessage outputMessage, Map<String, Object> hints) {
+
+		return this.writer.write(inputStream, elementType, mediaType, outputMessage, hints);
+	}
+
+	@Override
+	public List<MediaType> getWritableMediaTypes() {
+		return this.writer.getWritableMediaTypes();
+	}
+
+	@Override
+	public final Map<String, Object> resolveWriteHints(ResolvableType streamType,
+			ResolvableType elementType, MediaType mediaType, ServerHttpRequest request) {
+
+		Map<String, Object> hints = new HashMap<>();
+		if (this.writer instanceof ServerHttpMessageWriter) {
+			hints.putAll(((ServerHttpMessageWriter<T>)this.writer).resolveWriteHints(streamType, elementType, mediaType, request));
+		}
+		hints.putAll(resolveWriteHintsInternal(streamType, elementType, mediaType, request));
+		return hints;
+	}
+
+	/**
+	 * Abstract method that returns hints which can be used to customize how the body should be written.
+	 * Invoked from {@link #resolveWriteHints}.
+	 * @param streamType the original type used for the method return value. For annotation
+	 * based controllers, the {@link MethodParameter} is available via {@link ResolvableType#getSource()}.
+	 * @param elementType the stream element type to process
+	 * @param mediaType the content type to use when writing. May be {@code null} to
+	 * indicate that the default content type of the converter must be used.
+	 * @param request the current HTTP request
+	 * @return Additional information about how to write the body
+	 */
+	protected abstract Map<String, Object> resolveWriteHintsInternal(ResolvableType streamType,
+			ResolvableType elementType, MediaType mediaType, ServerHttpRequest request);
+
+}

spring-web/src/main/java/org/springframework/http/codec/ServerHttpMessageReader.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.http.codec;
+
+import java.util.Map;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
+import org.springframework.http.MediaType;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+
+/**
+ * Server and annotation based controller specific {@link HttpMessageReader} that allows to
+ * resolve hints using annotations or request based information.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+public interface ServerHttpMessageReader<T> extends HttpMessageReader<T> {
+
+	/**
+	 * Return hints that can be used to customize how the body should be read
+	 * @param streamType the original type used in the method parameter. For annotation
+	 * based controllers, the {@link MethodParameter} is available via {@link ResolvableType#getSource()}.
+	 * @param elementType the stream element type to return
+	 * @param mediaType the media type to read, can be {@code null} if not specified.
+	 * Typically the value of a {@code Content-Type} header.
+	 * @param request the current HTTP request
+	 * @return Additional information about how to read the body
+	 */
+	Map<String, Object> resolveReadHints(ResolvableType streamType, ResolvableType elementType,
+			MediaType mediaType, ServerHttpRequest request);
+
+}

spring-web/src/main/java/org/springframework/http/codec/ServerHttpMessageWriter.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.http.codec;
+
+import java.util.Map;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.core.ResolvableType;
+import org.springframework.http.MediaType;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+
+/**
+ * Server oriented {@link HttpMessageWriter} that allows to resolve hints using annotations or
+ * request based information.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+public interface ServerHttpMessageWriter<T> extends HttpMessageWriter<T> {
+
+	/**
+	 * Return hints that can be used to customize how the body should be written
+	 * @param streamType the original type used for the method return value. For annotation
+	 * based controllers, the {@link MethodParameter} is available via {@link ResolvableType#getSource()}.
+	 * @param elementType the stream element type to process
+	 * @param mediaType the content type to use when writing. May be {@code null} to
+	 * indicate that the default content type of the converter must be used.
+	 * @param request the current HTTP request
+	 * @return Additional information about how to write the body
+	 */
+	Map<String, Object> resolveWriteHints(ResolvableType streamType, ResolvableType elementType,
+			MediaType mediaType, ServerHttpRequest request);
+
+}