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

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 @@ public interface BodyExtractor<T, M extends ReactiveHttpInputMessage> {
 		 * @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 abstract class BodyExtractors {
 		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 abstract class BodyExtractors {
 		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 @@ public interface BodyInserter<T, M extends ReactiveHttpOutputMessage> {
 		 */
 		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 abstract class BodyInserters {
 		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 abstract class BodyInserters {
 		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 abstract class BodyInserters {
 		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 @@ public abstract class BodyInserters {
 					.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.ZoneId;
 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 @@ class DefaultClientRequestBuilder implements ClientRequest.BodyBuilder {
 				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 @@ package org.springframework.web.reactive.function.client;
 
 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 @@ class DefaultClientResponse implements ClientResponse {
 			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

@@ -78,6 +78,11 @@ class DefaultServerRequest implements ServerRequest {
 
 	@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() {
@@ -85,6 +90,10 @@ class DefaultServerRequest implements ServerRequest {
 					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.ZonedDateTime;
 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 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 		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 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 	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 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 
 		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 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 				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 abstract class RequestPredicates {
 			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.HttpHeaders;
 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 @@ import org.springframework.web.reactive.function.BodyExtractor;
  * {@link #body(BodyExtractor)} respectively.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 5.0
  */
 public interface ServerRequest {
@@ -71,9 +73,20 @@ public interface ServerRequest {
 	 * @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.HttpHeaders;
 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 @@ import org.springframework.web.server.ServerWebExchange;
  * {@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 @@ public interface ServerResponse {
 		 */
 		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 class ServerRequestWrapper implements ServerRequest {
 		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/test/java/org/springframework/web/reactive/function/BodyExtractorsTests.java

@@ -19,10 +19,14 @@ package org.springframework.web.reactive.function;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
+import com.fasterxml.jackson.annotation.JsonView;
 import org.junit.Before;
 import org.junit.Test;
 import reactor.core.publisher.Flux;
@@ -43,13 +47,20 @@ import org.springframework.http.codec.json.Jackson2JsonDecoder;
 import org.springframework.http.codec.xml.Jaxb2XmlDecoder;
 import org.springframework.mock.http.server.reactive.test.MockServerHttpRequest;
 
+import static org.springframework.http.codec.json.AbstractJackson2Codec.JSON_VIEW_HINT;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
 /**
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  */
 public class BodyExtractorsTests {
 
 	private BodyExtractor.Context context;
 
+	private Map<String, Object> hints;
+
 	@Before
 	public void createContext() {
 		final List<HttpMessageReader<?>> messageReaders = new ArrayList<>();
@@ -63,8 +74,12 @@ public class BodyExtractorsTests {
 			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
 				return messageReaders::stream;
 			}
+			@Override
+			public Map<String, Object> hints() {
+				return hints;
+			}
 		};
-
+		this.hints = new HashMap();
 	}
 
 	@Test
@@ -87,6 +102,31 @@ public class BodyExtractorsTests {
 				.verify();
 	}
 
+	@Test
+	public void toMonoWithHints() throws Exception {
+		BodyExtractor<Mono<User>, ReactiveHttpInputMessage> extractor = BodyExtractors.toMono(User.class);
+		this.hints.put(JSON_VIEW_HINT, SafeToDeserialize.class);
+
+		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+		DefaultDataBuffer dataBuffer =
+				factory.wrap(ByteBuffer.wrap("{\"username\":\"foo\",\"password\":\"bar\"}".getBytes(StandardCharsets.UTF_8)));
+		Flux<DataBuffer> body = Flux.just(dataBuffer);
+
+		MockServerHttpRequest request = new MockServerHttpRequest();
+		request.getHeaders().setContentType(MediaType.APPLICATION_JSON);
+		request.setBody(body);
+
+		Mono<User> result = extractor.extract(request, this.context);
+
+		StepVerifier.create(result)
+				.consumeNextWith(user -> {
+					assertEquals("foo", user.getUsername());
+					assertNull(user.getPassword());
+				})
+				.expectComplete()
+				.verify();
+	}
+
 	@Test
 	public void toFlux() throws Exception {
 		BodyExtractor<Flux<String>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(String.class);
@@ -107,6 +147,35 @@ public class BodyExtractorsTests {
 				.verify();
 	}
 
+	@Test
+	public void toFluxWithHints() throws Exception {
+		BodyExtractor<Flux<User>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(User.class);
+		this.hints.put(JSON_VIEW_HINT, SafeToDeserialize.class);
+
+		DefaultDataBufferFactory factory = new DefaultDataBufferFactory();
+		DefaultDataBuffer dataBuffer =
+				factory.wrap(ByteBuffer.wrap("[{\"username\":\"foo\",\"password\":\"bar\"},{\"username\":\"bar\",\"password\":\"baz\"}]".getBytes(StandardCharsets.UTF_8)));
+		Flux<DataBuffer> body = Flux.just(dataBuffer);
+
+		MockServerHttpRequest request = new MockServerHttpRequest();
+		request.getHeaders().setContentType(MediaType.APPLICATION_JSON);
+		request.setBody(body);
+
+		Flux<User> result = extractor.extract(request, this.context);
+
+		StepVerifier.create(result)
+				.consumeNextWith(user -> {
+					assertEquals("foo", user.getUsername());
+					assertNull(user.getPassword());
+				})
+				.consumeNextWith(user -> {
+					assertEquals("bar", user.getUsername());
+					assertNull(user.getPassword());
+				})
+				.expectComplete()
+				.verify();
+	}
+
 	@Test
 	public void toFluxUnacceptable() throws Exception {
 		BodyExtractor<Flux<String>, ReactiveHttpInputMessage> extractor = BodyExtractors.toFlux(String.class);
@@ -125,6 +194,10 @@ public class BodyExtractorsTests {
 			public Supplier<Stream<HttpMessageReader<?>>> messageReaders() {
 				return Stream::empty;
 			}
+			@Override
+			public Map<String, Object> hints() {
+				return Collections.emptyMap();
+			}
 		};
 
 		Flux<String> result = extractor.extract(request, emptyContext);
@@ -153,4 +226,39 @@ public class BodyExtractorsTests {
 				.verify();
 	}
 
+
+	interface SafeToDeserialize {}
+
+	private static class User {
+
+		@JsonView(SafeToDeserialize.class)
+		private String username;
+
+		private String password;
+
+		public User() {
+		}
+
+		public User(String username, String password) {
+			this.username = username;
+			this.password = password;
+		}
+
+		public String getUsername() {
+			return username;
+		}
+
+		public void setUsername(String username) {
+			this.username = username;
+		}
+
+		public String getPassword() {
+			return password;
+		}
+
+		public void setPassword(String password) {
+			this.password = password;
+		}
+	}
+
 }

spring-web-reactive/src/test/java/org/springframework/web/reactive/function/BodyInsertersTests.java

@@ -21,10 +21,13 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.function.Supplier;
 import java.util.stream.Stream;
 
+import com.fasterxml.jackson.annotation.JsonView;
 import org.junit.Before;
 import org.junit.Test;
 import reactor.core.publisher.Flux;
@@ -51,14 +54,18 @@ import org.springframework.mock.http.server.reactive.test.MockServerHttpResponse
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertArrayEquals;
+import static org.springframework.http.codec.json.AbstractJackson2Codec.JSON_VIEW_HINT;
 
 /**
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  */
 public class BodyInsertersTests {
 
 	private BodyInserter.Context context;
 
+	private Map<String, Object> hints;
+
 	@Before
 	public void createContext() {
 		final List<HttpMessageWriter<?>> messageWriters = new ArrayList<>();
@@ -71,19 +78,21 @@ public class BodyInsertersTests {
 		messageWriters
 				.add(new ServerSentEventHttpMessageWriter(Collections.singletonList(jsonEncoder)));
 
-
 		this.context = new BodyInserter.Context() {
 			@Override
 			public Supplier<Stream<HttpMessageWriter<?>>> messageWriters() {
 				return messageWriters::stream;
 			}
+			@Override
+			public Map<String, Object> hints() {
+				return hints;
+			}
 		};
-
+		this.hints = new HashMap();
 	}
 
-
 	@Test
-	public void ofObject() throws Exception {
+	public void ofString() throws Exception {
 		String body = "foo";
 		BodyInserter<String, ReactiveHttpOutputMessage> inserter = BodyInserters.fromObject(body);
 
@@ -99,6 +108,35 @@ public class BodyInsertersTests {
 				.verify();
 	}
 
+	@Test
+	public void ofObject() throws Exception {
+		User body = new User("foo", "bar");
+		BodyInserter<User, ReactiveHttpOutputMessage> inserter = BodyInserters.fromObject(body);
+		MockServerHttpResponse response = new MockServerHttpResponse();
+		Mono<Void> result = inserter.insert(response, this.context);
+		StepVerifier.create(result).expectComplete().verify();
+
+		StepVerifier.create(response.getBodyAsString())
+				.expectNext("{\"username\":\"foo\",\"password\":\"bar\"}")
+				.expectComplete()
+				.verify();
+	}
+
+	@Test
+	public void ofObjectWithHints() throws Exception {
+		User body = new User("foo", "bar");
+		BodyInserter<User, ReactiveHttpOutputMessage> inserter = BodyInserters.fromObject(body);
+		this.hints.put(JSON_VIEW_HINT, SafeToSerialize.class);
+		MockServerHttpResponse response = new MockServerHttpResponse();
+		Mono<Void> result = inserter.insert(response, this.context);
+		StepVerifier.create(result).expectComplete().verify();
+
+		StepVerifier.create(response.getBodyAsString())
+				.expectNext("{\"username\":\"foo\"}")
+				.expectComplete()
+				.verify();
+	}
+
 	@Test
 	public void ofPublisher() throws Exception {
 		Flux<String> body = Flux.just("foo");
@@ -180,4 +218,39 @@ public class BodyInsertersTests {
 	}
 
 
+	interface SafeToSerialize {}
+
+	private static class User {
+
+		@JsonView(SafeToSerialize.class)
+		private String username;
+
+		private String password;
+
+		public User() {
+		}
+
+		public User(String username, String password) {
+			this.username = username;
+			this.password = password;
+		}
+
+		public String getUsername() {
+			return username;
+		}
+
+		public void setUsername(String username) {
+			this.username = username;
+		}
+
+		public String getPassword() {
+			return password;
+		}
+
+		public void setPassword(String password) {
+			this.password = password;
+		}
+	}
+
+
 }

spring-web-reactive/src/test/java/org/springframework/web/reactive/function/server/MockServerRequest.java

@@ -99,6 +99,11 @@ public class MockServerRequest implements ServerRequest {
 		return (S) this.body;
 	}
 
+	@Override
+	public <S> S body(BodyExtractor<S, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
+		return (S) this.body;
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public <S> Mono<S> bodyToMono(Class<? extends S> elementClass) {

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

@@ -50,7 +50,7 @@ import org.springframework.util.MimeTypeUtils;
 public class ServerSentEventHttpMessageWriter implements HttpMessageWriter<Object> {
 
 	/**
-	 * Server-Sent Events hint expecting a {@link Boolean} value which when set to true
+	 * Server-Sent Events hint key expecting a {@link Boolean} value which when set to true
 	 * will adapt the content in order to comply with Server-Sent Events recommendation.
 	 * For example, it will append "data:" after each line break with data encoders
 	 * supporting it.

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Codec.java

@@ -38,6 +38,11 @@ import org.springframework.util.MimeType;
  */
 public class AbstractJackson2Codec {
 
+	/**
+	 * Hint key to use with a {@link Class} value specifying the JSON View to use to serialize
+	 * or deserialize an object.
+	 * @see <a href="http://wiki.fasterxml.com/JacksonJsonViews">Jackson JSON Views</a>
+	 */
 	public static final String JSON_VIEW_HINT = AbstractJackson2Codec.class.getName() + ".jsonView";
 
 	protected static final List<MimeType> JSON_MIME_TYPES = Arrays.asList(