Correlated encoding/decoding log messages via hints

Issue: SPR-16966

spring-core/src/main/java/org/springframework/core/codec/AbstractEncoder.java

@@ -18,7 +18,6 @@ package org.springframework.core.codec;
 
 import java.util.Arrays;
 import java.util.List;
-import java.util.Map;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -60,17 +59,4 @@ public abstract class AbstractEncoder<T> implements Encoder<T> {
 		return this.encodableMimeTypes.stream().anyMatch(candidate -> candidate.isCompatibleWith(mimeType));
 	}
 
-	/**
-	 * Helper method to obtain the logger to use from the Map of hints, or fall
-	 * back on the default logger. This may be used for example to override
-	 * logging, e.g. for a multipart request where the full map of part values
-	 * has already been logged.
-	 * @param hints the hints passed to the encode method
-	 * @return the logger to use
-	 * @since 5.1
-	 */
-	protected Log getLogger(@Nullable Map<String, Object> hints) {
-		return hints != null ? ((Log) hints.getOrDefault(Log.class.getName(), logger)) : logger;
-	}
-
 }

spring-core/src/main/java/org/springframework/core/codec/ByteArrayDecoder.java

@@ -54,7 +54,7 @@ public class ByteArrayDecoder extends AbstractDataBufferDecoder<byte[]> {
 		dataBuffer.read(result);
 		DataBufferUtils.release(dataBuffer);
 		if (logger.isDebugEnabled()) {
-			logger.debug("Read " + result.length + " bytes");
+			logger.debug(Hints.getLogPrefix(hints) + "Read " + result.length + " bytes");
 		}
 		return result;
 	}

spring-core/src/main/java/org/springframework/core/codec/ByteArrayEncoder.java

@@ -55,9 +55,10 @@ public class ByteArrayEncoder extends AbstractEncoder<byte[]> {
 
 		return Flux.from(inputStream).map(bytes -> {
 			DataBuffer dataBuffer = bufferFactory.wrap(bytes);
-			Log logger = getLogger(hints);
-			if (logger.isDebugEnabled()) {
-				logger.debug("Writing " + dataBuffer.readableByteCount() + " bytes");
+			Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+			if (theLogger.isDebugEnabled()) {
+				theLogger.debug(Hints.getLogPrefix(hints) +
+						"Writing " + dataBuffer.readableByteCount() + " bytes");
 			}
 			return dataBuffer;
 		});

spring-core/src/main/java/org/springframework/core/codec/ByteBufferDecoder.java

@@ -58,7 +58,7 @@ public class ByteBufferDecoder extends AbstractDataBufferDecoder<ByteBuffer> {
 		copy.flip();
 		DataBufferUtils.release(dataBuffer);
 		if (logger.isDebugEnabled()) {
-			logger.debug("Read " + byteCount + " bytes");
+			logger.debug(Hints.getLogPrefix(hints) + "Read " + byteCount + " bytes");
 		}
 		return copy;
 	}

spring-core/src/main/java/org/springframework/core/codec/ByteBufferEncoder.java

@@ -56,9 +56,10 @@ public class ByteBufferEncoder extends AbstractEncoder<ByteBuffer> {
 
 		return Flux.from(inputStream).map(byteBuffer -> {
 			DataBuffer dataBuffer = bufferFactory.wrap(byteBuffer);
-			Log logger = getLogger(hints);
-			if (logger.isDebugEnabled()) {
-				logger.debug("Writing " + dataBuffer.readableByteCount() + " bytes");
+			Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+			if (theLogger.isDebugEnabled()) {
+				theLogger.debug(Hints.getLogPrefix(hints) +
+						"Writing " + dataBuffer.readableByteCount() + " bytes");
 			}
 			return dataBuffer;
 		});

spring-core/src/main/java/org/springframework/core/codec/CharSequenceEncoder.java

@@ -69,9 +69,9 @@ public final class CharSequenceEncoder extends AbstractEncoder<CharSequence> {
 		Charset charset = getCharset(mimeType);
 
 		return Flux.from(inputStream).map(charSequence -> {
-			Log logger = getLogger(hints);
-			if (logger.isDebugEnabled()) {
-				logger.debug("Writing '" + charSequence + "'");
+			Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+			if (theLogger.isDebugEnabled()) {
+				theLogger.debug(Hints.getLogPrefix(hints) + "Writing '" + charSequence + "'");
 			}
 			CharBuffer charBuffer = CharBuffer.wrap(charSequence);
 			ByteBuffer byteBuffer = charset.encode(charBuffer);

spring-core/src/main/java/org/springframework/core/codec/DataBufferDecoder.java

@@ -63,7 +63,7 @@ public class DataBufferDecoder extends AbstractDataBufferDecoder<DataBuffer> {
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
 		if (logger.isDebugEnabled()) {
-			logger.debug("Read " + buffer.readableByteCount() + " bytes");
+			logger.debug(Hints.getLogPrefix(hints) + "Read " + buffer.readableByteCount() + " bytes");
 		}
 		return buffer;
 	}

spring-core/src/main/java/org/springframework/core/codec/DataBufferEncoder.java

@@ -55,9 +55,11 @@ public class DataBufferEncoder extends AbstractEncoder<DataBuffer> {
 
 		Flux<DataBuffer> flux = Flux.from(inputStream);
 
-		Log logger = getLogger(hints);
-		if (logger.isDebugEnabled()) {
-			flux = flux.doOnNext(buffer -> logger.debug("Writing " + buffer.readableByteCount() + " bytes"));
+		Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+		if (theLogger.isDebugEnabled()) {
+			flux = flux.doOnNext(buffer ->
+					theLogger.debug(Hints.getLogPrefix(hints) +
+							"Writing " + buffer.readableByteCount() + " bytes"));
 		}
 
 		return flux;

spring-core/src/main/java/org/springframework/core/codec/Hints.java

+/*
+ * Copyright 2002-2018 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.core.codec;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.apache.commons.logging.Log;
+
+import org.springframework.lang.Nullable;
+
+/**
+ * Constants and convenience methods for working with hints.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ * @see ResourceRegionEncoder#BOUNDARY_STRING_HINT
+ */
+public abstract class Hints {
+
+	/**
+	 * Name of hint exposing a prefix to use for correlating log messages.
+	 * @since 5.1
+	 */
+	public static final String LOG_PREFIX_HINT = Log.class.getName() + ".PREFIX";
+
+	/**
+	 * Name of hint for a preferred {@link Log logger} to use. This can be used
+	 * by a composite encoder (e.g. multipart requests) to control or suppress
+	 * logging by individual part encoders.
+	 * @since 5.1
+	 */
+	public static final String LOGGER_HINT = Log.class.getName();
+
+
+	/**
+	 * Create a map wit a single hint via {@link Collections#singletonMap}.
+	 * @param hintName the hint name
+	 * @param value the hint value
+	 * @return the created map
+	 */
+	public static Map<String, Object> from(String hintName, Object value) {
+		return Collections.singletonMap(hintName, value);
+	}
+
+	/**
+	 * Return an empty map of hints via {@link Collections#emptyMap()}.
+	 * @return the empty map
+	 */
+	public static Map<String, Object> none() {
+		return Collections.emptyMap();
+	}
+
+	/**
+	 * Obtain the value for a required hint.
+	 * @param hints the hints map
+	 * @param hintName the required hint name
+	 * @param <T> the hint type to cast to
+	 * @return the hint value
+	 * @throws IllegalArgumentException if the hint is not found
+	 */
+	@SuppressWarnings("unchecked")
+	public static <T> T getRequiredHint(@Nullable Map<String, Object> hints, String hintName) {
+		if (hints == null) {
+			throw new IllegalArgumentException("No hints map for required hint '" + hintName + "'");
+		}
+		T hint = (T) hints.get(hintName);
+		if (hint == null) {
+			throw new IllegalArgumentException("Hints map must contain the hint '" + hintName + "'");
+		}
+		return hint;
+	}
+
+	/**
+	 * Obtain the hint {@link #LOG_PREFIX_HINT}, if present, or an empty String.
+	 * @param hints the hints passed to the encode method
+	 * @return the log prefix
+	 */
+	public static String getLogPrefix(@Nullable Map<String, Object> hints) {
+		return hints != null ? (String) hints.getOrDefault(LOG_PREFIX_HINT, "") : "";
+	}
+
+	/**
+	 * Obtain the hint {@link #LOGGER_HINT}, if present, or the given logger.
+	 * @param hints the hints passed to the encode method
+	 * @param defaultLogger the logger to return if a hint is not found
+	 * @return the logger to use
+	 */
+	public static Log getLoggerOrDefault(@Nullable Map<String, Object> hints, Log defaultLogger) {
+		return hints != null ? (Log) hints.getOrDefault(LOGGER_HINT, defaultLogger) : defaultLogger;
+	}
+
+	/**
+	 * Merge two maps of hints, creating and copying into a new map if both have
+	 * values, or returning the non-empty map, or an empty map if both are empty.
+	 * @param hints1 1st map of hints
+	 * @param hints2 2nd map of hints
+	 * @return a single map with hints from both
+	 */
+	public static Map<String, Object> merge(Map<String, Object> hints1, Map<String, Object> hints2) {
+		if (hints1.isEmpty() && hints2.isEmpty()) {
+			return Collections.emptyMap();
+		}
+		else if (hints2.isEmpty()) {
+			return hints1;
+		}
+		else if (hints1.isEmpty()) {
+			return hints2;
+		}
+		else {
+			Map<String, Object> result = new HashMap<>(hints1.size() + hints2.size());
+			result.putAll(hints1);
+			result.putAll(hints2);
+			return result;
+		}
+	}
+
+	/**
+	 * Merge a single hint into a map of hints, possibly creating and copying
+	 * all hints into a new map, or otherwise if the map of hints is empty,
+	 * creating a new single entry map.
+	 * @param hints a map of hints to be merge
+	 * @param hintName the hint name to merge
+	 * @param hintValue the hint value to merge
+	 * @return a single map with all hints
+	 */
+	public static Map<String, Object> merge(Map<String, Object> hints, String hintName, Object hintValue) {
+		if (hints.isEmpty()) {
+			return Collections.singletonMap(hintName, hintValue);
+		}
+		else {
+			Map<String, Object> result = new HashMap<>(hints.size() + 1);
+			result.putAll(hints);
+			result.put(hintName, hintValue);
+			return result;
+		}
+	}
+
+}

spring-core/src/main/java/org/springframework/core/codec/ResourceDecoder.java

@@ -73,7 +73,7 @@ public class ResourceDecoder extends AbstractDataBufferDecoder<Resource> {
 		Assert.state(clazz != null, "No resource class");
 
 		if (logger.isDebugEnabled()) {
-			logger.debug("Read " + bytes.length + " bytes");
+			logger.debug(Hints.getLogPrefix(hints) + "Read " + bytes.length + " bytes");
 		}
 
 		if (InputStreamResource.class == clazz) {

spring-core/src/main/java/org/springframework/core/codec/ResourceEncoder.java

@@ -69,9 +69,9 @@ public class ResourceEncoder extends AbstractSingleValueEncoder<Resource> {
 	protected Flux<DataBuffer> encode(Resource resource, DataBufferFactory dataBufferFactory,
 			ResolvableType type, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
-		Log logger = getLogger(hints);
-		if (logger.isDebugEnabled()) {
-			logger.debug("Writing [" + resource + "]");
+		Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+		if (theLogger.isDebugEnabled()) {
+			theLogger.debug(Hints.getLogPrefix(hints) + "Writing [" + resource + "]");
 		}
 
 		return DataBufferUtils.read(resource, dataBufferFactory, this.bufferSize);

spring-core/src/main/java/org/springframework/core/codec/ResourceRegionEncoder.java

@@ -91,10 +91,7 @@ public class ResourceRegionEncoder extends AbstractEncoder<ResourceRegion> {
 					.flatMapMany(region -> writeResourceRegion(region, bufferFactory, hints));
 		}
 		else {
-			Assert.notNull(hints, "'hints' must not be null");
-			Assert.isTrue(hints.containsKey(BOUNDARY_STRING_HINT), "'hints' must contain boundaryString hint");
-			final String boundaryString = (String) hints.get(BOUNDARY_STRING_HINT);
-
+			final String boundaryString = Hints.getRequiredHint(hints, BOUNDARY_STRING_HINT);
 			byte[] startBoundary = getAsciiBytes("\r\n--" + boundaryString + "\r\n");
 			byte[] contentType =
 					(mimeType != null ? getAsciiBytes("Content-Type: " + mimeType + "\r\n") : new byte[0]);
@@ -126,9 +123,10 @@ public class ResourceRegionEncoder extends AbstractEncoder<ResourceRegion> {
 		long position = region.getPosition();
 		long count = region.getCount();
 
-		Log logger = getLogger(hints);
-		if (logger.isDebugEnabled()) {
-			logger.debug("Writing region " + position + "-" + (position + count) + " of [" + resource + "]");
+		Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+		if (theLogger.isDebugEnabled()) {
+			theLogger.debug(Hints.getLogPrefix(hints) +
+					"Writing region " + position + "-" + (position + count) + " of [" + resource + "]");
 		}
 
 		Flux<DataBuffer> in = DataBufferUtils.read(resource, position, bufferFactory, this.bufferSize);
@@ -149,7 +147,8 @@ public class ResourceRegionEncoder extends AbstractEncoder<ResourceRegion> {
 		long end = start + region.getCount() - 1;
 		OptionalLong contentLength = contentLength(region.getResource());
 		if (contentLength.isPresent()) {
-			return getAsciiBytes("Content-Range: bytes " + start + '-' + end + '/' + contentLength.getAsLong() + "\r\n\r\n");
+			long length = contentLength.getAsLong();
+			return getAsciiBytes("Content-Range: bytes " + start + '-' + end + '/' + length + "\r\n\r\n");
 		}
 		else {
 			return getAsciiBytes("Content-Range: bytes " + start + '-' + end + "\r\n\r\n");

spring-core/src/main/java/org/springframework/core/codec/StringDecoder.java

@@ -207,7 +207,7 @@ public final class StringDecoder extends AbstractDataBufferDecoder<String> {
 		DataBufferUtils.release(dataBuffer);
 		String value = charBuffer.toString();
 		if (logger.isDebugEnabled()) {
-			logger.debug("Decoded '" + value + "'");
+			logger.debug(Hints.getLogPrefix(hints) + "Decoded '" + value + "'");
 		}
 		return value;
 	}

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

@@ -16,8 +16,6 @@
 
 package org.springframework.http.codec;
 
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -26,6 +24,7 @@ import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Decoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.HttpMessage;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpInputMessage;
@@ -114,9 +113,8 @@ public class DecoderHttpMessageReader<T> implements HttpMessageReader<T> {
 	public Flux<T> read(ResolvableType actualType, ResolvableType elementType,
 			ServerHttpRequest request, ServerHttpResponse response, Map<String, Object> hints) {
 
-		Map<String, Object> allHints = new HashMap<>(4);
-		allHints.putAll(getReadHints(actualType, elementType, request, response));
-		allHints.putAll(hints);
+		Map<String, Object> allHints = Hints.merge(hints,
+				getReadHints(actualType, elementType, request, response));
 
 		return read(elementType, request, allHints);
 	}
@@ -125,9 +123,8 @@ public class DecoderHttpMessageReader<T> implements HttpMessageReader<T> {
 	public Mono<T> readMono(ResolvableType actualType, ResolvableType elementType,
 			ServerHttpRequest request, ServerHttpResponse response, Map<String, Object> hints) {
 
-		Map<String, Object> allHints = new HashMap<>(4);
-		allHints.putAll(getReadHints(actualType, elementType, request, response));
-		allHints.putAll(hints);
+		Map<String, Object> allHints = Hints.merge(hints,
+				getReadHints(actualType, elementType, request, response));
 
 		return readMono(elementType, request, allHints);
 	}
@@ -141,10 +138,10 @@ public class DecoderHttpMessageReader<T> implements HttpMessageReader<T> {
 			ResolvableType elementType, ServerHttpRequest request, ServerHttpResponse response) {
 
 		if (this.decoder instanceof HttpMessageDecoder) {
-			HttpMessageDecoder<?> httpDecoder = (HttpMessageDecoder<?>) this.decoder;
-			return httpDecoder.getDecodeHints(actualType, elementType, request, response);
+			HttpMessageDecoder<?> decoder = (HttpMessageDecoder<?>) this.decoder;
+			return decoder.getDecodeHints(actualType, elementType, request, response);
 		}
-		return Collections.emptyMap();
+		return Hints.none();
 	}
 
 }

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

@@ -16,8 +16,6 @@
 
 package org.springframework.http.codec;
 
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -27,6 +25,7 @@ import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.MediaType;
@@ -159,9 +158,8 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 			ResolvableType elementType, @Nullable MediaType mediaType, ServerHttpRequest request,
 			ServerHttpResponse response, Map<String, Object> hints) {
 
-		Map<String, Object> allHints = new HashMap<>();
-		allHints.putAll(getWriteHints(actualType, elementType, mediaType, request, response));
-		allHints.putAll(hints);
+		Map<String, Object> allHints = Hints.merge(hints,
+				getWriteHints(actualType, elementType, mediaType, request, response));
 
 		return write(inputStream, elementType, mediaType, response, allHints);
 	}
@@ -175,10 +173,10 @@ public class EncoderHttpMessageWriter<T> implements HttpMessageWriter<T> {
 			@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
 
 		if (this.encoder instanceof HttpMessageEncoder) {
-			HttpMessageEncoder<?> httpEncoder = (HttpMessageEncoder<?>) this.encoder;
-			return httpEncoder.getEncodeHints(streamType, elementType, mediaType, request, response);
+			HttpMessageEncoder<?> encoder = (HttpMessageEncoder<?>) this.encoder;
+			return encoder.getEncodeHints(streamType, elementType, mediaType, request, response);
 		}
-		return Collections.emptyMap();
+		return Hints.none();
 	}
 
 }

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

@@ -29,6 +29,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpInputMessage;
@@ -108,7 +109,7 @@ public class FormHttpMessageReader extends LoggingCodecSupport
 					DataBufferUtils.release(buffer);
 					MultiValueMap<String, String> formData = parseFormData(charset, body);
 					if (shouldLogRequestDetails()) {
-						logger.debug("Decoded " + formData);
+						logger.debug(Hints.getLogPrefix(hints) + "Decoded " + formData);
 					}
 					return formData;
 				});

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

@@ -29,6 +29,7 @@ import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.MediaType;
 import org.springframework.http.ReactiveHttpOutputMessage;
@@ -131,7 +132,7 @@ public class FormHttpMessageWriter extends LoggingCodecSupport
 
 		return Mono.from(inputStream).flatMap(form -> {
 			if (shouldLogRequestDetails()) {
-				logger.debug("Encoding " + form);
+				logger.debug(Hints.getLogPrefix(hints) + "Encoding " + form);
 			}
 			String value = serializeForm(form, charset);
 			ByteBuffer byteBuffer = charset.encode(value);

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

@@ -16,12 +16,12 @@
 
 package org.springframework.http.codec;
 
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.MediaType;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
@@ -58,7 +58,7 @@ public interface HttpMessageEncoder<T> extends Encoder<T> {
 	default Map<String, Object> getEncodeHints(ResolvableType actualType, ResolvableType elementType,
 			@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
 
-		return Collections.emptyMap();
+		return Hints.none();
 	}
 
 }

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

@@ -18,8 +18,6 @@ package org.springframework.http.codec;
 
 import java.io.File;
 import java.io.IOException;
-import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -31,6 +29,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.codec.ResourceDecoder;
 import org.springframework.core.codec.ResourceEncoder;
 import org.springframework.core.codec.ResourceRegionEncoder;
@@ -119,7 +118,7 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 			ReactiveHttpOutputMessage message, Map<String, Object> hints) {
 
 		HttpHeaders headers = message.getHeaders();
-		MediaType resourceMediaType = getResourceMediaType(mediaType, resource);
+		MediaType resourceMediaType = getResourceMediaType(mediaType, resource, hints);
 		headers.setContentType(resourceMediaType);
 
 		if (headers.getContentLength() < 0) {
@@ -129,7 +128,7 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 			}
 		}
 
-		return zeroCopy(resource, null, message)
+		return zeroCopy(resource, null, message, hints)
 				.orElseGet(() -> {
 					Mono<Resource> input = Mono.just(resource);
 					DataBufferFactory factory = message.bufferFactory();
@@ -138,13 +137,15 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 				});
 	}
 
-	private static MediaType getResourceMediaType(@Nullable MediaType mediaType, Resource resource) {
+	private static MediaType getResourceMediaType(
+			@Nullable MediaType mediaType, Resource resource, Map<String, Object> hints) {
+
 		if (mediaType != null && mediaType.isConcrete() && !mediaType.equals(MediaType.APPLICATION_OCTET_STREAM)) {
 			return mediaType;
 		}
 		mediaType = MediaTypeFactory.getMediaType(resource).orElse(MediaType.APPLICATION_OCTET_STREAM);
 		if (logger.isDebugEnabled()) {
-			logger.debug("Resource associated with '" + mediaType + "'");
+			logger.debug(Hints.getLogPrefix(hints) + "Resource associated with '" + mediaType + "'");
 		}
 		return mediaType;
 	}
@@ -162,7 +163,7 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 	}
 
 	private static Optional<Mono<Void>> zeroCopy(Resource resource, @Nullable ResourceRegion region,
-			ReactiveHttpOutputMessage message) {
+			ReactiveHttpOutputMessage message, Map<String, Object> hints) {
 
 		if (message instanceof ZeroCopyHttpOutputMessage && resource.isFile()) {
 			try {
@@ -171,7 +172,7 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 				long count = region != null ? region.getCount() : file.length();
 				if (logger.isDebugEnabled()) {
 					String formatted = region != null ? "region " + pos + "-" + (count) + " of " : "";
-					logger.debug("Zero-copy " + formatted + "[" + resource + "]");
+					logger.debug(Hints.getLogPrefix(hints) + "Zero-copy " + formatted + "[" + resource + "]");
 				}
 				return Optional.of(((ZeroCopyHttpOutputMessage) message).writeWith(file, pos, count));
 			}
@@ -211,7 +212,7 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 
 			response.setStatusCode(HttpStatus.PARTIAL_CONTENT);
 			List<ResourceRegion> regions = HttpRange.toResourceRegions(ranges, resource);
-			MediaType resourceMediaType = getResourceMediaType(mediaType, resource);
+			MediaType resourceMediaType = getResourceMediaType(mediaType, resource, hints);
 
 			if (regions.size() == 1){
 				ResourceRegion region = regions.get(0);
@@ -224,26 +225,26 @@ public class ResourceHttpMessageWriter implements HttpMessageWriter<Resource> {
 					headers.add("Content-Range", "bytes " + start + '-' + end + '/' + contentLength);
 					headers.setContentLength(end - start + 1);
 				}
-				return writeSingleRegion(region, response);
+				return writeSingleRegion(region, response, hints);
 			}
 			else {
 				String boundary = MimeTypeUtils.generateMultipartBoundaryString();
 				MediaType multipartType = MediaType.parseMediaType("multipart/byteranges;boundary=" + boundary);
 				headers.setContentType(multipartType);
-				Map<String, Object> theHints = new HashMap<>(hints);
-				theHints.put(ResourceRegionEncoder.BOUNDARY_STRING_HINT, boundary);
-				return encodeAndWriteRegions(Flux.fromIterable(regions), resourceMediaType, response, theHints);
+				Map<String, Object> allHints = Hints.merge(hints, ResourceRegionEncoder.BOUNDARY_STRING_HINT, boundary);
+				return encodeAndWriteRegions(Flux.fromIterable(regions), resourceMediaType, response, allHints);
 			}
 		});
 	}
 
-	private Mono<Void> writeSingleRegion(ResourceRegion region, ReactiveHttpOutputMessage message) {
+	private Mono<Void> writeSingleRegion(ResourceRegion region, ReactiveHttpOutputMessage message,
+			Map<String, Object> hints) {
 
-		return zeroCopy(region.getResource(), region, message)
+		return zeroCopy(region.getResource(), region, message, hints)
 				.orElseGet(() -> {
 					Publisher<? extends ResourceRegion> input = Mono.just(region);
 					MediaType mediaType = message.getHeaders().getContentType();
-					return encodeAndWriteRegions(input, mediaType, message, Collections.emptyMap());
+					return encodeAndWriteRegions(input, mediaType, message, hints);
 				});
 	}
 

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

@@ -105,7 +105,7 @@ public class ServerSentEventHttpMessageReader implements HttpMessageReader<Objec
 		boolean shouldWrap = isServerSentEvent(elementType);
 		ResolvableType valueType = (shouldWrap ? elementType.getGeneric() : elementType);
 
-		return stringDecoder.decode(message.getBody(), STRING_TYPE, null, Collections.emptyMap())
+		return stringDecoder.decode(message.getBody(), STRING_TYPE, null, hints)
 				.bufferUntil(line -> line.equals(""))
 				.concatMap(lines -> buildEvent(lines, valueType, shouldWrap, hints));
 	}

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

@@ -19,7 +19,6 @@ package org.springframework.http.codec;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -30,6 +29,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.http.MediaType;
@@ -188,9 +188,8 @@ public class ServerSentEventHttpMessageWriter implements HttpMessageWriter<Objec
 			@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response,
 			Map<String, Object> hints) {
 
-		Map<String, Object> allHints = new HashMap<>();
-		allHints.putAll(getEncodeHints(actualType, elementType, mediaType, request, response));
-		allHints.putAll(hints);
+		Map<String, Object> allHints = Hints.merge(hints,
+				getEncodeHints(actualType, elementType, mediaType, request, response));
 
 		return write(input, elementType, mediaType, response, allHints);
 	}
@@ -199,10 +198,10 @@ public class ServerSentEventHttpMessageWriter implements HttpMessageWriter<Objec
 			@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
 
 		if (this.encoder instanceof HttpMessageEncoder) {
-			HttpMessageEncoder<?> httpEncoder = (HttpMessageEncoder<?>) this.encoder;
-			return httpEncoder.getEncodeHints(actualType, elementType, mediaType, request, response);
+			HttpMessageEncoder<?> encoder = (HttpMessageEncoder<?>) this.encoder;
+			return encoder.getEncodeHints(actualType, elementType, mediaType, request, response);
 		}
-		return Collections.emptyMap();
+		return Hints.none();
 	}
 
 }

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.java

@@ -36,6 +36,7 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.DecodingException;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.codec.HttpMessageDecoder;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -112,7 +113,7 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 			try {
 				Object value = reader.readValue(tokenBuffer.asParser(getObjectMapper()));
 				if (logger.isDebugEnabled()) {
-					logger.debug("Decoded [" + value + "]");
+					logger.debug(Hints.getLogPrefix(hints) +"Decoded [" + value + "]");
 				}
 				return value;
 			}

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Encoder.java

@@ -42,6 +42,7 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.EncodingException;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.http.MediaType;
@@ -141,9 +142,9 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 	private DataBuffer encodeValue(Object value, @Nullable MimeType mimeType, DataBufferFactory bufferFactory,
 			ResolvableType elementType, @Nullable Map<String, Object> hints, JsonEncoding encoding) {
 
-		Log logger = getLogger(hints);
-		if (logger.isDebugEnabled()) {
-			logger.debug("Encoding [" + value + "]");
+		Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+		if (theLogger.isDebugEnabled()) {
+			theLogger.debug(Hints.getLogPrefix(hints) + "Encoding [" + value + "]");
 		}
 
 		JavaType javaType = getJavaType(elementType.getType(), null);
@@ -218,7 +219,7 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 	public Map<String, Object> getEncodeHints(@Nullable ResolvableType actualType, ResolvableType elementType,
 			@Nullable MediaType mediaType, ServerHttpRequest request, ServerHttpResponse response) {
 
-		return (actualType != null ? getHints(actualType) : Collections.emptyMap());
+		return (actualType != null ? getHints(actualType) : Hints.none());
 	}
 
 	// Jackson2CodecSupport ...

spring-web/src/main/java/org/springframework/http/codec/json/Jackson2CodecSupport.java

@@ -34,6 +34,7 @@ import org.apache.commons.logging.LogFactory;
 import org.springframework.core.GenericTypeResolver;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.MimeType;
@@ -98,19 +99,6 @@ public abstract class Jackson2CodecSupport {
 		return (mimeType == null || this.mimeTypes.stream().anyMatch(m -> m.isCompatibleWith(mimeType)));
 	}
 
-	/**
-	 * Helper method to obtain the logger to use from the Map of hints, or fall
-	 * back on the default logger. This may be used for example to override
-	 * logging, e.g. for a multipart request where the full map of part values
-	 * has already been logged.
-	 * @param hints the hints passed to the encode method
-	 * @return the logger to use
-	 * @since 5.1
-	 */
-	protected Log getLogger(@Nullable Map<String, Object> hints) {
-		return hints != null ? ((Log) hints.getOrDefault(Log.class.getName(), logger)) : logger;
-	}
-
 	protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {
 		TypeFactory typeFactory = this.objectMapper.getTypeFactory();
 		return typeFactory.constructType(GenericTypeResolver.resolveType(type, contextClass));
@@ -123,10 +111,10 @@ public abstract class Jackson2CodecSupport {
 			if (annotation != null) {
 				Class<?>[] classes = annotation.value();
 				Assert.isTrue(classes.length == 1, JSON_VIEW_HINT_ERROR + param);
-				return Collections.singletonMap(JSON_VIEW_HINT, classes[0]);
+				return Hints.from(JSON_VIEW_HINT, classes[0]);
 			}
 		}
-		return Collections.emptyMap();
+		return Hints.none();
 	}
 
 	@Nullable

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

@@ -29,7 +29,6 @@ import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
-import org.apache.commons.logging.Log;
 import org.apache.commons.logging.impl.NoOpLog;
 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
@@ -38,6 +37,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.CharSequenceEncoder;
 import org.springframework.core.codec.CodecException;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
@@ -87,8 +87,7 @@ public class MultipartHttpMessageWriter extends LoggingCodecSupport
 	public static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;
 
 	/** Suppress logging from individual part writers (full map logged at this level). */
-	private static final Map<String, Object> DEFAULT_HINTS =
-			Collections.singletonMap(Log.class.getName(), new NoOpLog());
+	private static final Map<String, Object> DEFAULT_HINTS = Hints.from(Hints.LOGGER_HINT, new NoOpLog());
 
 
 	private final List<HttpMessageWriter<?>> partWriters;
@@ -191,7 +190,7 @@ public class MultipartHttpMessageWriter extends LoggingCodecSupport
 
 		return Mono.from(inputStream).flatMap(map -> {
 			if (this.formWriter == null || isMultipart(map, mediaType)) {
-				return writeMultipart(map, outputMessage);
+				return writeMultipart(map, outputMessage, hints);
 			}
 			else {
 				@SuppressWarnings("unchecked")
@@ -216,7 +215,9 @@ public class MultipartHttpMessageWriter extends LoggingCodecSupport
 		return false;
 	}
 
-	private Mono<Void> writeMultipart(MultiValueMap<String, ?> map, ReactiveHttpOutputMessage outputMessage) {
+	private Mono<Void> writeMultipart(
+			MultiValueMap<String, ?> map, ReactiveHttpOutputMessage outputMessage, Map<String, Object> hints) {
+
 		byte[] boundary = generateMultipartBoundary();
 
 		Map<String, String> params = new HashMap<>(2);
@@ -226,7 +227,7 @@ public class MultipartHttpMessageWriter extends LoggingCodecSupport
 		outputMessage.getHeaders().setContentType(new MediaType(MediaType.MULTIPART_FORM_DATA, params));
 
 		if (shouldLogRequestDetails()) {
-			logger.debug("Encoding " + map);
+			logger.debug(Hints.getLogPrefix(hints) + "Encoding " + map);
 		}
 
 		Flux<DataBuffer> body = Flux.fromIterable(map.entrySet())

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

@@ -45,6 +45,7 @@ import reactor.core.publisher.FluxSink;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DataBufferUtils;
@@ -95,7 +96,7 @@ public class SynchronossPartHttpMessageReader extends LoggingCodecSupport implem
 		return Flux.create(new SynchronossPartGenerator(message, this.bufferFactory, this.streamStorageFactory))
 				.doOnNext(part -> {
 					if (shouldLogRequestDetails()) {
-						logger.debug("Decoded [" + part + "]");
+						logger.debug(Hints.getLogPrefix(hints) + "Decoded [" + part + "]");
 					}
 				});
 	}

spring-web/src/main/java/org/springframework/http/codec/xml/Jaxb2XmlDecoder.java

@@ -40,6 +40,7 @@ import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.AbstractDecoder;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.DecodingException;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -107,7 +108,7 @@ public class Jaxb2XmlDecoder extends AbstractDecoder<Object> {
 		return splitEvents.map(events -> {
 			Object value = unmarshal(events, outputClass);
 			if (logger.isDebugEnabled()) {
-				logger.debug("Decoded [" + value + "]");
+				logger.debug(Hints.getLogPrefix(hints) + "Decoded [" + value + "]");
 			}
 			return value;
 		});

spring-web/src/main/java/org/springframework/http/codec/xml/Jaxb2XmlEncoder.java

@@ -32,6 +32,7 @@ import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.AbstractSingleValueEncoder;
 import org.springframework.core.codec.CodecException;
 import org.springframework.core.codec.EncodingException;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.lang.Nullable;
@@ -74,9 +75,9 @@ public class Jaxb2XmlEncoder extends AbstractSingleValueEncoder<Object> {
 	protected Flux<DataBuffer> encode(Object value, DataBufferFactory dataBufferFactory,
 			ResolvableType type, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 		try {
-			Log logger = getLogger(hints);
-			if (logger.isDebugEnabled()) {
-				logger.debug("Encoding [" + value + "]");
+			Log theLogger = Hints.getLoggerOrDefault(hints, logger);
+			if (theLogger.isDebugEnabled()) {
+				theLogger.debug(Hints.getLogPrefix(hints) + "Encoding [" + value + "]");
 			}
 			DataBuffer buffer = dataBufferFactory.allocateBuffer(1024);
 			OutputStream outputStream = buffer.asOutputStream();

spring-web/src/main/java/org/springframework/web/server/ServerWebExchange.java

@@ -44,9 +44,9 @@ import org.springframework.util.MultiValueMap;
 public interface ServerWebExchange {
 
 	/**
-	 * Name of {@link #getAttributes() attribute} whose value correlates log
-	 * messages for the exchange. Use {@link #getLogPrefix()} to obtain a
-	 * consistently formatted prefix based on this attribute.
+	 * Name of {@link #getAttributes() attribute} whose value can be used to
+	 * correlate log messages for this exchange. Use {@link #getLogPrefix()} to
+	 * obtain a consistently formatted prefix based on this attribute.
 	 * @since 5.1
 	 * @see #getLogPrefix()
 	 */
@@ -219,9 +219,10 @@ public interface ServerWebExchange {
 	void addUrlTransformer(Function<String, String> transformer);
 
 	/**
-	 * Return a common prefix to use for log messages related to the exchange.
-	 * The prefix is based on the value of the {@link #LOG_ID_ATTRIBUTE}
-	 * attribute along with some extra formatting.
+	 * Return a log message prefix to use to correlate messages for this exchange.
+	 * The prefix is based on the value of the attribute {@link #LOG_ID_ATTRIBUTE}
+	 * along with some extra formatting so that the prefix can be conveniently
+	 * prepended with no further formatting no separatorns required.
 	 * @return the log message prefix or an empty String if the
 	 * {@link #LOG_ID_ATTRIBUTE} is not set.
 	 * @since 5.1

spring-web/src/main/java/org/springframework/web/server/adapter/DefaultServerWebExchange.java

@@ -20,7 +20,6 @@ import java.security.Principal;
 import java.time.Instant;
 import java.time.temporal.ChronoUnit;
 import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
@@ -31,6 +30,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.i18n.LocaleContext;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.HttpStatus;
@@ -141,7 +141,7 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 						.filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
 						.findFirst()
 						.orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
-						.readMono(FORM_DATA_TYPE, request, Collections.emptyMap())
+						.readMono(FORM_DATA_TYPE, request, Hints.none())
 						.switchIfEmpty(EMPTY_FORM_DATA)
 						.cache();
 			}
@@ -163,7 +163,7 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 						.filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
 						.findFirst()
 						.orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
-						.readMono(MULTIPART_DATA_TYPE, request, Collections.emptyMap())
+						.readMono(MULTIPART_DATA_TYPE, request, Hints.none())
 						.switchIfEmpty(EMPTY_MULTIPART_DATA)
 						.cache();
 			}

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

@@ -458,8 +458,7 @@ public abstract class BodyInserters {
 					findWriter(context, MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA);
 			MultiValueMap<String, HttpEntity<?>> body = this.builder.build();
 			return messageWriter.write(Mono.just(body), MULTIPART_DATA_TYPE,
-					MediaType.MULTIPART_FORM_DATA,
-					outputMessage, context.hints());
+					MediaType.MULTIPART_FORM_DATA, outputMessage, context.hints());
 		}
 	}
 

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

@@ -28,6 +28,7 @@ import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -251,7 +252,7 @@ final class DefaultClientRequestBuilder implements ClientRequest.Builder {
 				}
 				@Override
 				public Map<String, Object> hints() {
-					return Collections.emptyMap();
+					return Hints.none();
 				}
 			});
 		}

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

@@ -26,6 +26,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBufferUtils;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpStatus;
@@ -95,7 +96,7 @@ class DefaultClientResponse implements ClientResponse {
 			}
 			@Override
 			public Map<String, Object> hints() {
-				return Collections.emptyMap();
+				return Hints.none();
 			}
 		});
 	}

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

@@ -31,6 +31,7 @@ import java.util.function.Consumer;
 
 import reactor.core.publisher.Mono;
 
+import org.springframework.core.codec.Hints;
 import org.springframework.http.CacheControl;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -236,6 +237,7 @@ class DefaultEntityResponseBuilder<T> implements EntityResponse.Builder<T> {
 				}
 				@Override
 				public Map<String, Object> hints() {
+					hints.put(Hints.LOG_PREFIX_HINT, exchange.getLogPrefix());
 					return hints;
 				}
 			});

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

@@ -33,6 +33,7 @@ import reactor.core.publisher.Flux;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.HttpCookie;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpRange;
@@ -123,11 +124,16 @@ class DefaultServerRequest implements ServerRequest {
 
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor) {
-		return body(extractor, Collections.emptyMap());
+		return bodyInternal(extractor, Hints.from(Hints.LOG_PREFIX_HINT, exchange().getLogPrefix()));
 	}
 
 	@Override
 	public <T> T body(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
+		hints = Hints.merge(hints, Hints.LOG_PREFIX_HINT, exchange().getLogPrefix());
+		return bodyInternal(extractor, hints);
+	}
+
+	private <T> T bodyInternal(BodyExtractor<T, ? super ServerHttpRequest> extractor, Map<String, Object> hints) {
 		return extractor.extract(request(),
 				new BodyExtractor.Context() {
 					@Override

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

@@ -20,7 +20,6 @@ import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.security.Principal;
 import java.time.Instant;
-import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -35,6 +34,7 @@ import reactor.core.publisher.Mono;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.i18n.LocaleContext;
 import org.springframework.core.ResolvableType;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.core.io.buffer.DataBufferFactory;
 import org.springframework.core.io.buffer.DataBufferUtils;
@@ -320,7 +320,7 @@ class DefaultServerRequestBuilder implements ServerRequest.Builder {
 							.filter(reader -> reader.canRead(FORM_DATA_TYPE, MediaType.APPLICATION_FORM_URLENCODED))
 							.findFirst()
 							.orElseThrow(() -> new IllegalStateException("No form data HttpMessageReader.")))
-							.readMono(FORM_DATA_TYPE, request, Collections.emptyMap())
+							.readMono(FORM_DATA_TYPE, request, Hints.none())
 							.switchIfEmpty(EMPTY_FORM_DATA)
 							.cache();
 				}
@@ -342,7 +342,7 @@ class DefaultServerRequestBuilder implements ServerRequest.Builder {
 							.filter(reader -> reader.canRead(MULTIPART_DATA_TYPE, MediaType.MULTIPART_FORM_DATA))
 							.findFirst()
 							.orElseThrow(() -> new IllegalStateException("No multipart HttpMessageReader.")))
-							.readMono(MULTIPART_DATA_TYPE, request, Collections.emptyMap())
+							.readMono(MULTIPART_DATA_TYPE, request, Hints.none())
 							.switchIfEmpty(EMPTY_MULTIPART_DATA)
 							.cache();
 				}

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

@@ -34,6 +34,7 @@ import org.reactivestreams.Publisher;
 import reactor.core.publisher.Mono;
 
 import org.springframework.core.ParameterizedTypeReference;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.CacheControl;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -399,6 +400,7 @@ class DefaultServerResponseBuilder implements ServerResponse.BodyBuilder {
 				}
 				@Override
 				public Map<String, Object> hints() {
+					hints.put(Hints.LOG_PREFIX_HINT, exchange.getLogPrefix());
 					return hints;
 				}
 			});

spring-webflux/src/main/java/org/springframework/web/reactive/resource/ResourceWebHandler.java

@@ -23,11 +23,8 @@ import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.EnumSet;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
-import java.util.function.Supplier;
 import java.util.stream.Collectors;
 
 import org.apache.commons.logging.Log;
@@ -36,7 +33,7 @@ import reactor.core.publisher.Mono;
 
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.ResolvableType;
-import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.Resource;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.http.CacheControl;
@@ -372,7 +369,8 @@ public class ResourceWebHandler implements WebHandler, InitializingBean {
 						Assert.state(writer != null, "No ResourceHttpMessageWriter");
 						return writer.write(Mono.just(resource),
 								null, ResolvableType.forClass(Resource.class), mediaType,
-								exchange.getRequest(), exchange.getResponse(), Collections.emptyMap());
+								exchange.getRequest(), exchange.getResponse(),
+								Hints.from(Hints.LOG_PREFIX_HINT, exchange.getLogPrefix()));
 					}
 					catch (IOException ex) {
 						return Mono.error(ex);

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

@@ -17,7 +17,6 @@
 package org.springframework.web.reactive.result.method.annotation;
 
 import java.lang.annotation.Annotation;
-import java.util.Collections;
 import java.util.EnumSet;
 import java.util.List;
 import java.util.Map;
@@ -34,7 +33,7 @@ import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.annotation.AnnotationUtils;
 import org.springframework.core.codec.DecodingException;
-import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.core.io.buffer.DataBuffer;
 import org.springframework.http.HttpMethod;
 import org.springframework.http.MediaType;
@@ -161,7 +160,7 @@ public abstract class AbstractMessageReaderArgumentResolver extends HandlerMetho
 
 		for (HttpMessageReader<?> reader : getMessageReaders()) {
 			if (reader.canRead(elementType, mediaType)) {
-				Map<String, Object> readHints = Collections.emptyMap();
+				Map<String, Object> readHints = Hints.from(Hints.LOG_PREFIX_HINT, exchange.getLogPrefix());
 				if (adapter != null && adapter.isMultiValue()) {
 					if (logger.isDebugEnabled()) {
 						logger.debug(exchange.getLogPrefix() + "0..N [" + elementType + "]");

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

@@ -16,9 +16,7 @@
 
 package org.springframework.web.reactive.result.method.annotation;
 
-import java.util.Collections;
 import java.util.List;
-import java.util.Map;
 import java.util.stream.Collectors;
 
 import org.reactivestreams.Publisher;
@@ -28,7 +26,7 @@ import org.springframework.core.MethodParameter;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
-import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.HttpMessageWriter;
 import org.springframework.http.server.reactive.ServerHttpRequest;
@@ -149,8 +147,8 @@ public abstract class AbstractMessageWriterResultHandler extends HandlerResultHa
 			}
 			for (HttpMessageWriter<?> writer : getMessageWriters()) {
 				if (writer.canWrite(elementType, bestMediaType)) {
-					return writer.write((Publisher) publisher, actualType, elementType,
-							bestMediaType, request, response, Collections.emptyMap());
+					return writer.write((Publisher) publisher, actualType, elementType, bestMediaType,
+							request, response, Hints.from(Hints.LOG_PREFIX_HINT, logPrefix));
 				}
 			}
 		}

spring-webflux/src/main/java/org/springframework/web/reactive/result/view/HttpMessageWriterView.java

@@ -16,7 +16,6 @@
 
 package org.springframework.web.reactive.result.view;
 
-import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -28,6 +27,7 @@ import reactor.core.publisher.Mono;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.core.codec.Encoder;
+import org.springframework.core.codec.Hints;
 import org.springframework.http.MediaType;
 import org.springframework.http.codec.EncoderHttpMessageWriter;
 import org.springframework.http.codec.HttpMessageWriter;
@@ -161,7 +161,8 @@ public class HttpMessageWriterView implements View {
 		Publisher<T> input = Mono.justOrEmpty(value);
 		ResolvableType elementType = ResolvableType.forClass(value.getClass());
 		return ((HttpMessageWriter<T>) this.writer).write(
-				input, elementType, contentType, exchange.getResponse(), Collections.emptyMap());
+				input, elementType, contentType, exchange.getResponse(),
+				Hints.from(Hints.LOG_PREFIX_HINT, exchange.getLogPrefix()));
 	}
 
 }