MIME types by Class for Encoder, Decoder, HttpMessageReader|Writer

Closes gh-26212

Author: rstoyanchev

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.core.codec;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
@@ -59,7 +60,7 @@ public interface Decoder<T> {
 	 * this type must have been previously passed to the {@link #canDecode}
 	 * method and it must have returned {@code true}.
 	 * @param mimeType the MIME type associated with the input stream (optional)
-	 * @param hints additional information about how to do encode
+	 * @param hints additional information about how to do decode
 	 * @return the output stream with decoded elements
 	 */
 	Flux<T> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
@@ -72,7 +73,7 @@ Flux<T> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
 	 * this type must have been previously passed to the {@link #canDecode}
 	 * method and it must have returned {@code true}.
 	 * @param mimeType the MIME type associated with the input stream (optional)
-	 * @param hints additional information about how to do encode
+	 * @param hints additional information about how to do decode
 	 * @return the output stream with the decoded element
 	 */
 	Mono<T> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementType,
@@ -85,7 +86,7 @@ Mono<T> decodeToMono(Publisher<DataBuffer> inputStream, ResolvableType elementTy
 	 * @param buffer the {@code DataBuffer} to decode
 	 * @param targetType the expected output type
 	 * @param mimeType the MIME type associated with the data
-	 * @param hints additional information about how to do encode
+	 * @param hints additional information about how to do decode
 	 * @return the decoded value, possibly {@code null}
 	 * @since 5.2
 	 */
@@ -111,8 +112,27 @@ default T decode(DataBuffer buffer, ResolvableType targetType,
 	}
 
 	/**
-	 * Return the list of MIME types this decoder supports.
+	 * Return the list of MIME types supported by this Decoder. The list may not
+	 * apply to every possible target element type and calls to this method
+	 * should typically be guarded via {@link #canDecode(ResolvableType, MimeType)
+	 * canDecode(elementType, null)}. The list may also exclude MIME types
+	 * supported only for a specific element type. Alternatively, use
+	 * {@link #getDecodableMimeTypes(ResolvableType)} for a more precise list.
+	 * @return the list of supported MIME types
 	 */
 	List<MimeType> getDecodableMimeTypes();
 
+	/**
+	 * Return the list of MIME types supported by this Decoder for the given type
+	 * of element. This list may differ from {@link #getDecodableMimeTypes()}
+	 * if the Decoder doesn't support the given element type or if it supports
+	 * it only for a subset of MIME types.
+	 * @param targetType the type of element to check for decoding
+	 * @return the list of MIME types supported for the given target type
+	 * @since 5.3.4
+	 */
+	default List<MimeType> getDecodableMimeTypes(ResolvableType targetType) {
+		return (canDecode(targetType, null) ? getDecodableMimeTypes() : Collections.emptyList());
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.core.codec;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -90,8 +91,27 @@ default DataBuffer encodeValue(T value, DataBufferFactory bufferFactory,
 	}
 
 	/**
-	 * Return the list of mime types this encoder supports.
+	 * Return the list of MIME types supported by this Encoder. The list may not
+	 * apply to every possible target element type and calls to this method should
+	 * typically be guarded via {@link #canEncode(ResolvableType, MimeType)
+	 * canEncode(elementType, null)}. The list may also exclude MIME types
+	 * supported only for a specific element type. Alternatively, use
+	 * {@link #getEncodableMimeTypes(ResolvableType)} for a more precise list.
+	 * @return the list of supported MIME types
 	 */
 	List<MimeType> getEncodableMimeTypes();
 
+	/**
+	 * Return the list of MIME types supported by this Encoder for the given type
+	 * of element. This list may differ from the {@link #getEncodableMimeTypes()}
+	 * if the Encoder doesn't support the element type or if it supports it only
+	 * for a subset of MIME types.
+	 * @param elementType the type of element to check for encoding
+	 * @return the list of MIME types supported for the given element type
+	 * @since 5.3.4
+	 */
+	default List<MimeType> getEncodableMimeTypes(ResolvableType elementType) {
+		return (canEncode(elementType, null) ? getEncodableMimeTypes() : Collections.emptyList());
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -87,6 +87,10 @@ public List<MediaType> getReadableMediaTypes() {
 		return this.mediaTypes;
 	}
 
+	@Override
+	public List<MediaType> getReadableMediaTypes(ResolvableType elementType) {
+		return MediaType.asMediaTypes(this.decoder.getDecodableMimeTypes(elementType));
+	}
 
 	@Override
 	public boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -105,6 +105,10 @@ public List<MediaType> getWritableMediaTypes() {
 		return this.mediaTypes;
 	}
 
+	@Override
+	public List<MediaType> getWritableMediaTypes(ResolvableType elementType) {
+		return MediaType.asMediaTypes(getEncoder().getEncodableMimeTypes(elementType));
+	}
 
 	@Override
 	public boolean canWrite(ResolvableType elementType, @Nullable MediaType mediaType) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.http.codec;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -43,10 +44,29 @@
 public interface HttpMessageReader<T> {
 
 	/**
-	 * Return the {@link MediaType}'s that this reader supports.
+	 * Return the list of media types supported by this reader. The list may not
+	 * apply to every possible target element type and calls to this method
+	 * should typically be guarded via {@link #canRead(ResolvableType, MediaType)
+	 * canWrite(elementType, null)}. The list may also exclude media types
+	 * supported only for a specific element type. Alternatively, use
+	 * {@link #getReadableMediaTypes(ResolvableType)} for a more precise list.
+	 * @return the general list of supported media types
 	 */
 	List<MediaType> getReadableMediaTypes();
 
+	/**
+	 * Return the list of media types supported by this Reader for the given type
+	 * of element. This list may differ from {@link #getReadableMediaTypes()}
+	 * if the Reader doesn't support the element type, or if it supports it
+	 * only for a subset of media types.
+	 * @param elementType the type of element to read
+	 * @return the list of media types supported for the given class
+	 * @since 5.3.4
+	 */
+	default List<MediaType> getReadableMediaTypes(ResolvableType elementType) {
+		return (canRead(elementType, null) ? getReadableMediaTypes() : Collections.emptyList());
+	}
+
 	/**
 	 * Whether the given object type is supported by this reader.
 	 * @param elementType the type of object to check
@@ -56,7 +76,7 @@ public interface HttpMessageReader<T> {
 	boolean canRead(ResolvableType elementType, @Nullable MediaType mediaType);
 
 	/**
-	 * Read from the input message and encode to a stream of objects.
+	 * Read from the input message and decode to a stream of objects.
 	 * @param elementType the type of objects in the stream which must have been
 	 * previously checked via {@link #canRead(ResolvableType, MediaType)}
 	 * @param message the message to read from
@@ -66,7 +86,7 @@ public interface HttpMessageReader<T> {
 	Flux<T> read(ResolvableType elementType, ReactiveHttpInputMessage message, Map<String, Object> hints);
 
 	/**
-	 * Read from the input message and encode to a single object.
+	 * Read from the input message and decode to a single object.
 	 * @param elementType the type of objects in the stream which must have been
 	 * previously checked via {@link #canRead(ResolvableType, MediaType)}
 	 * @param message the message to read from

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -16,6 +16,7 @@
 
 package org.springframework.http.codec;
 
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 
@@ -43,10 +44,29 @@
 public interface HttpMessageWriter<T> {
 
 	/**
-	 * Return the {@link MediaType}'s that this writer supports.
+	 * Return the list of media types supported by this Writer. The list may not
+	 * apply to every possible target element type and calls to this method should
+	 * typically be guarded via {@link #canWrite(ResolvableType, MediaType)
+	 * canWrite(elementType, null)}. The list may also exclude media types
+	 * supported only for a specific element type. Alternatively, use
+	 * {@link #getWritableMediaTypes(ResolvableType)} for a more precise list.
+	 * @return the general list of supported media types
 	 */
 	List<MediaType> getWritableMediaTypes();
 
+	/**
+	 * Return the list of media types supported by this Writer for the given type
+	 * of element. This list may differ from {@link #getWritableMediaTypes()}
+	 * if the Writer doesn't support the element type, or if it supports it
+	 * only for a subset of media types.
+	 * @param elementType the type of element to encode
+	 * @return the list of media types supported for the given class
+	 * @since 5.3.4
+	 */
+	default List<MediaType> getWritableMediaTypes(ResolvableType elementType) {
+		return (canWrite(elementType, null) ? getWritableMediaTypes() : Collections.emptyList());
+	}
+
 	/**
 	 * Whether the given object type is supported by this writer.
 	 * @param elementType the type of object to check

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

@@ -259,6 +259,10 @@ public List<MimeType> getDecodableMimeTypes() {
 		return getMimeTypes();
 	}
 
+	@Override
+	public List<MimeType> getDecodableMimeTypes(ResolvableType targetType) {
+		return getMimeTypes(targetType);
+	}
 
 	// Jackson2CodecSupport
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -357,6 +357,11 @@ public List<MimeType> getEncodableMimeTypes() {
 		return getMimeTypes();
 	}
 
+	@Override
+	public List<MimeType> getEncodableMimeTypes(ResolvableType elementType) {
+		return getMimeTypes(elementType);
+	}
+
 	@Override
 	public List<MediaType> getStreamingMediaTypes() {
 		return Collections.unmodifiableList(this.streamingMediaTypes);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -18,6 +18,7 @@
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
@@ -148,7 +149,7 @@ public Map<MimeType, ObjectMapper> getObjectMappersForType(Class<?> clazz) {
 		return Collections.emptyMap();
 	}
 
-	private Map<Class<?>, Map<MimeType, ObjectMapper>> getObjectMapperRegistrations() {
+	protected Map<Class<?>, Map<MimeType, ObjectMapper>> getObjectMapperRegistrations() {
 		return (this.objectMapperRegistrations != null ? this.objectMapperRegistrations : Collections.emptyMap());
 	}
 
@@ -159,6 +160,17 @@ protected List<MimeType> getMimeTypes() {
 		return this.mimeTypes;
 	}
 
+	protected List<MimeType> getMimeTypes(ResolvableType elementType) {
+		Class<?> elementClass = elementType.toClass();
+		List<MimeType> result = null;
+		for (Map.Entry<Class<?>, Map<MimeType, ObjectMapper>> entry : getObjectMapperRegistrations().entrySet()) {
+			if (entry.getKey().isAssignableFrom(elementClass)) {
+				result = (result != null ? result : new ArrayList<>(entry.getValue().size()));
+				result.addAll(entry.getValue().keySet());
+			}
+		}
+		return (CollectionUtils.isEmpty(result) ? getMimeTypes() : result);
+	}
 
 	protected boolean supportsMimeType(@Nullable MimeType mimeType) {
 		if (mimeType == null) {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -196,7 +196,7 @@ private static <T, S extends Publisher<T>> S readWithMessageReaders(
 				.map(readerFunction)
 				.orElseGet(() -> {
 					List<MediaType> mediaTypes = context.messageReaders().stream()
-							.flatMap(reader -> reader.getReadableMediaTypes().stream())
+							.flatMap(reader -> reader.getReadableMediaTypes(elementType).stream())
 							.collect(Collectors.toList());
 					return errorFunction.apply(
 							new UnsupportedMediaTypeException(contentType, mediaTypes, elementType));

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 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.
@@ -385,7 +385,7 @@ private static UnsupportedMediaTypeException unsupportedError(ResolvableType bod
 			BodyInserter.Context context, @Nullable MediaType mediaType) {
 
 		List<MediaType> supportedMediaTypes = context.messageWriters().stream()
-				.flatMap(reader -> reader.getWritableMediaTypes().stream())
+				.flatMap(reader -> reader.getWritableMediaTypes(bodyType).stream())
 				.collect(Collectors.toList());
 
 		return new UnsupportedMediaTypeException(mediaType, supportedMediaTypes, bodyType);