Allow to specify hints with the functional web API

The most common use case is specifying JSON views.

ServerResponse.BodyBuilder#hint(String, Object) allows to
specify response body serialization hints.

ServerRequest#body(BodyExtractor, Map) allows to specify
request body extraction hints.

Issue: SPR-15030

Author: sdeleuze

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/BodyExtractor.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.reactive.function;
 
+import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
@@ -52,6 +53,11 @@ interface Context {
 		 * @return the stream of message readers
 		 */
 		Supplier<Stream<HttpMessageReader<?>>> messageReaders();
+
+		/**
+		 * Return the map of hints to use to customize body extraction.
+		 */
+		Map<String, Object> hints();
 	}
 
 }

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/BodyExtractors.java

@@ -65,7 +65,7 @@ public static <T> BodyExtractor<Mono<T>, ReactiveHttpInputMessage> toMono(Resolv
 		Assert.notNull(elementType, "'elementType' must not be null");
 		return (request, context) -> readWithMessageReaders(request, context,
 				elementType,
-				reader -> reader.readMono(elementType, request, Collections.emptyMap()),
+				reader -> reader.readMono(elementType, request, context.hints()),
 				Mono::error);
 	}
 
@@ -90,7 +90,7 @@ public static <T> BodyExtractor<Flux<T>, ReactiveHttpInputMessage> toFlux(Resolv
 		Assert.notNull(elementType, "'elementType' must not be null");
 		return (inputMessage, context) -> readWithMessageReaders(inputMessage, context,
 				elementType,
-				reader -> reader.read(elementType, inputMessage, Collections.emptyMap()),
+				reader -> reader.read(elementType, inputMessage, context.hints()),
 				Flux::error);
 	}
 

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/BodyInserter.java

@@ -16,6 +16,7 @@
 
 package org.springframework.web.reactive.function;
 
+import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
@@ -54,6 +55,11 @@ interface Context {
 		 */
 		Supplier<Stream<HttpMessageWriter<?>>> messageWriters();
 
+		/**
+		 * Return the map of hints to use for response body conversion.
+		 */
+		Map<String, Object> hints();
+
 	}
 
 

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/BodyInserters.java

@@ -16,7 +16,6 @@
 
 package org.springframework.web.reactive.function;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
@@ -119,7 +118,7 @@ public static <T extends Resource> BodyInserter<T, ReactiveHttpOutputMessage> fr
 		return (response, context) -> {
 					HttpMessageWriter<Resource> messageWriter = resourceHttpMessageWriter(context);
 					return messageWriter.write(Mono.just(resource), RESOURCE_TYPE, null,
-							response, Collections.emptyMap());
+							response, context.hints());
 				};
 	}
 
@@ -146,7 +145,7 @@ public static <T, S extends Publisher<ServerSentEvent<T>>> BodyInserter<S, Serve
 		return (response, context) -> {
 					HttpMessageWriter<ServerSentEvent<T>> messageWriter = sseMessageWriter(context);
 					return messageWriter.write(eventsPublisher, SERVER_SIDE_EVENT_TYPE,
-							MediaType.TEXT_EVENT_STREAM, response, Collections.emptyMap());
+							MediaType.TEXT_EVENT_STREAM, response, context.hints());
 				};
 	}
 
@@ -186,7 +185,7 @@ public static <T, S extends Publisher<T>> BodyInserter<S, ServerHttpResponse> fr
 		return (outputMessage, context) -> {
 					HttpMessageWriter<T> messageWriter = sseMessageWriter(context);
 					return messageWriter.write(eventsPublisher, eventType,
-							MediaType.TEXT_EVENT_STREAM, outputMessage, Collections.emptyMap());
+							MediaType.TEXT_EVENT_STREAM, outputMessage, context.hints());
 
 				};
 	}
@@ -227,8 +226,7 @@ private static <T, P extends Publisher<?>, M extends ReactiveHttpOutputMessage>
 					.findFirst()
 					.map(BodyInserters::cast)
 					.map(messageWriter -> messageWriter
-							.write(body, bodyType, contentType, m, Collections
-									.emptyMap()))
+							.write(body, bodyType, contentType, m, context.hints()))
 					.orElseGet(() -> {
 						List<MediaType> supportedMediaTypes = messageWriters.get()
 								.flatMap(reader -> reader.getWritableMediaTypes().stream())

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/client/DefaultClientRequestBuilder.java

@@ -22,6 +22,8 @@
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.util.Arrays;
+import java.util.Collections;
+import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
@@ -220,6 +222,11 @@ public Mono<Void> writeTo(ClientHttpRequest request, WebClientStrategies strateg
 				public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
 					return strategies.messageWriters();
 				}
+
+				@Override
+				public Map<String, Object> hints() {
+					return Collections.emptyMap();
+				}
 			});
 		}
 	}

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/client/DefaultClientResponse.java

@@ -18,6 +18,7 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.OptionalLong;
 import java.util.function.Function;
@@ -74,6 +75,10 @@ public <T> T body(BodyExtractor<T, ? super ClientHttpResponse> extractor) {
 			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
 				return strategies.messageReaders();
 			}
+			@Override
+			public Map<String, Object> hints() {
+				return Collections.emptyMap();
+			}
 		});
 	}
 

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/DefaultServerRequest.java

@@ -78,13 +78,22 @@ public Headers headers() {
 
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
+		return body(extractor, Collections.emptyMap());
+	}
+
+	@Override
+	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
 		Assert.notNull(extractor, "'extractor' must not be null");
 		return extractor.extract(request(),
 				new BodyExtractor.Context() {
 					@Override
 					public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
 						return DefaultServerRequest.this.strategies.messageReaders();
 					}
+					@Override
+					public Map<String, Object> hints() {
+						return hints;
+					}
 				});
 	}
 

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/DefaultServerResponseBuilder.java

@@ -22,6 +22,7 @@
 import java.time.format.DateTimeFormatter;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.Locale;
@@ -62,6 +63,8 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 
 	private final HttpHeaders headers = new HttpHeaders();
 
+	private final Map<String, Object> hints = new HashMap<>();
+
 
 	public DefaultServerResponseBuilder(HttpStatus statusCode) {
 		this.statusCode = statusCode;
@@ -122,6 +125,12 @@ public ServerResponse.BodyBuilder eTag(String eTag) {
 		return this;
 	}
 
+	@Override
+	public ServerResponse.BodyBuilder hint(String key, Object value) {
+		this.hints.put(key, value);
+		return this;
+	}
+
 	@Override
 	public ServerResponse.BodyBuilder lastModified(ZonedDateTime lastModified) {
 		ZonedDateTime gmt = lastModified.withZoneSameInstant(ZoneId.of("GMT"));
@@ -182,7 +191,7 @@ public <T, P extends Publisher<T>> Mono<ServerResponse> body(P publisher,
 	public <T> Mono<ServerResponse> body(BodyInserter<T, ? super ServerHttpResponse> inserter) {
 		Assert.notNull(inserter, "'inserter' must not be null");
 		return Mono
-				.just(new BodyInserterServerResponse<T>(this.statusCode, this.headers, inserter));
+				.just(new BodyInserterServerResponse<T>(this.statusCode, this.headers, inserter, this.hints));
 	}
 
 	@Override
@@ -276,11 +285,14 @@ private static final class BodyInserterServerResponse<T> extends AbstractServerR
 
 		private final BodyInserter<T, ? super ServerHttpResponse> inserter;
 
+		private final Map<String, Object> hints;
+
 		public BodyInserterServerResponse(HttpStatus statusCode, HttpHeaders headers,
-				BodyInserter<T, ? super ServerHttpResponse> inserter) {
+				BodyInserter<T, ? super ServerHttpResponse> inserter, Map<String, Object> hints) {
 
 			super(statusCode, headers);
 			this.inserter = inserter;
+			this.hints = hints;
 		}
 
 		@Override
@@ -292,6 +304,10 @@ public Mono<Void> writeTo(ServerWebExchange exchange, HandlerStrategies strategi
 				public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
 					return strategies.messageWriters();
 				}
+				@Override
+				public Map<String, Object> hints() {
+					return hints;
+				}
 			});
 		}
 	}

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/RequestPredicates.java

@@ -323,6 +323,11 @@ public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
 			return this.request.body(extractor);
 		}
 
+		@Override
+		public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
+			return this.request.body(extractor, hints);
+		}
+
 		@Override
 		public <T> Mono<T> bodyToMono(Class<? extends T> elementClass) {
 			return this.request.bodyToMono(elementClass);

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/ServerRequest.java

@@ -31,6 +31,7 @@
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpRange;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.json.AbstractJackson2Codec;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.web.reactive.function.BodyExtractor;
 
@@ -40,6 +41,7 @@
  * {@link #body(BodyExtractor)} respectively.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.0
  */
 public interface ServerRequest {
@@ -71,9 +73,20 @@ default String path() {
 	 * @param extractor the {@code BodyExtractor} that reads from the request
 	 * @param <T> the type of the body returned
 	 * @return the extracted body
+	 * @see #body(BodyExtractor, Map)
 	 */
 	<T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor);
 
+	/**
+	 * Extract the body with the given {@code BodyExtractor} and hints.
+	 * @param extractor the {@code BodyExtractor} that reads from the request
+	 * @param hints the map of hints like {@link AbstractJackson2Codec#JSON_VIEW_HINT}
+	 * to use to customize body extraction
+	 * @param <T> the type of the body returned
+	 * @return the extracted body
+	 */
+	<T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints);
+
 	/**
 	 * Extract the body to a {@code Mono}.
 	 * @param elementClass the class of element in the {@code Mono}

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/ServerResponse.java

@@ -31,6 +31,7 @@
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.MediaType;
+import org.springframework.http.codec.json.AbstractJackson2Codec;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.Assert;
 import org.springframework.web.reactive.function.BodyInserter;
@@ -42,6 +43,7 @@
  * {@linkplain HandlerFunction handler function} or {@linkplain HandlerFilterFunction filter function}.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.0
  */
 public interface ServerResponse {
@@ -312,6 +314,12 @@ interface BodyBuilder extends HeadersBuilder<BodyBuilder> {
 		 */
 		BodyBuilder contentType(MediaType contentType);
 
+		/**
+		 * Add a serialization hint like {@link AbstractJackson2Codec#JSON_VIEW_HINT} to
+		 * customize how the body will be serialized.
+		 */
+		BodyBuilder hint(String key, Object value);
+
 		/**
 		 * Set the body of the response to the given {@code Publisher} and return it. This
 		 * convenience method combines {@link #body(BodyInserter)} and

spring-web-reactive/src/main/java/org/springframework/web/reactive/function/server/support/ServerRequestWrapper.java

@@ -91,6 +91,11 @@ public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
 		return this.request.body(extractor);
 	}
 
+	@Override
+	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
+		return this.request.body(extractor, hints);
+	}
+
 	@Override
 	public <T> Mono<T> bodyToMono(Class<? extends T> elementClass) {
 		return this.request.bodyToMono(elementClass);