Extra ObjectMapper registrations in Jackson2CodecSupport

See gh-26212

spring-web/src/main/java/org/springframework/http/codec/json/AbstractJackson2Decoder.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.
@@ -98,17 +98,21 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 
 	@Override
 	public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		JavaType javaType = getObjectMapper().constructType(elementType.getType());
+		ObjectMapper mapper = selectObjectMapper(elementType, mimeType);
+		if (mapper == null) {
+			return false;
+		}
+		JavaType javaType = mapper.constructType(elementType.getType());
 		// Skip String: CharSequenceDecoder + "*/*" comes after
 		if (CharSequence.class.isAssignableFrom(elementType.toClass()) || !supportsMimeType(mimeType)) {
 			return false;
 		}
 		if (!logger.isDebugEnabled()) {
-			return getObjectMapper().canDeserialize(javaType);
+			return mapper.canDeserialize(javaType);
 		}
 		else {
 			AtomicReference<Throwable> causeRef = new AtomicReference<>();
-			if (getObjectMapper().canDeserialize(javaType, causeRef)) {
+			if (mapper.canDeserialize(javaType, causeRef)) {
 				return true;
 			}
 			logWarningIfNecessary(javaType, causeRef.get());
@@ -120,7 +124,10 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 	public Flux<Object> decode(Publisher<DataBuffer> input, ResolvableType elementType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
-		ObjectMapper mapper = getObjectMapper();
+		ObjectMapper mapper = selectObjectMapper(elementType, mimeType);
+		if (mapper == null) {
+			throw new IllegalStateException("No ObjectMapper for " + elementType);
+		}
 
 		boolean forceUseOfBigDecimal = mapper.isEnabled(DeserializationFeature.USE_BIG_DECIMAL_FOR_FLOATS);
 		if (BigDecimal.class.equals(elementType.getType())) {
@@ -131,11 +138,11 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 		Flux<TokenBuffer> tokens = Jackson2Tokenizer.tokenize(processed, mapper.getFactory(), mapper,
 				true, forceUseOfBigDecimal, getMaxInMemorySize());
 
-		ObjectReader reader = getObjectReader(elementType, hints);
+		ObjectReader reader = getObjectReader(mapper, elementType, hints);
 
 		return tokens.handle((tokenBuffer, sink) -> {
 			try {
-				Object value = reader.readValue(tokenBuffer.asParser(getObjectMapper()));
+				Object value = reader.readValue(tokenBuffer.asParser(mapper));
 				logValue(value, hints);
 				if (value != null) {
 					sink.next(value);
@@ -176,8 +183,13 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 	public Object decode(DataBuffer dataBuffer, ResolvableType targetType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) throws DecodingException {
 
+		ObjectMapper mapper = selectObjectMapper(targetType, mimeType);
+		if (mapper == null) {
+			throw new IllegalStateException("No ObjectMapper for " + targetType);
+		}
+
 		try {
-			ObjectReader objectReader = getObjectReader(targetType, hints);
+			ObjectReader objectReader = getObjectReader(mapper, targetType, hints);
 			Object value = objectReader.readValue(dataBuffer.asInputStream());
 			logValue(value, hints);
 			return value;
@@ -190,7 +202,9 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 		}
 	}
 
-	private ObjectReader getObjectReader(ResolvableType elementType, @Nullable Map<String, Object> hints) {
+	private ObjectReader getObjectReader(
+			ObjectMapper mapper, ResolvableType elementType, @Nullable Map<String, Object> hints) {
+
 		Assert.notNull(elementType, "'elementType' must not be null");
 		Class<?> contextClass = getContextClass(elementType);
 		if (contextClass == null && hints != null) {
@@ -199,8 +213,8 @@ public abstract class AbstractJackson2Decoder extends Jackson2CodecSupport imple
 		JavaType javaType = getJavaType(elementType.getType(), contextClass);
 		Class<?> jsonView = (hints != null ? (Class<?>) hints.get(Jackson2CodecSupport.JSON_VIEW_HINT) : null);
 		return jsonView != null ?
-				getObjectMapper().readerWithView(jsonView).forType(javaType) :
+				mapper.readerWithView(jsonView).forType(javaType) :
-				getObjectMapper().readerFor(javaType);
+				mapper.readerFor(javaType);
 	}
 
 	@Nullable

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

@@ -104,7 +104,6 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 
 	@Override
 	public boolean canEncode(ResolvableType elementType, @Nullable MimeType mimeType) {
-		Class<?> clazz = elementType.toClass();
 		if (!supportsMimeType(mimeType)) {
 			return false;
 		}
@@ -114,6 +113,11 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 				return false;
 			}
 		}
+		ObjectMapper mapper = selectObjectMapper(elementType, mimeType);
+		if (mapper == null) {
+			return false;
+		}
+		Class<?> clazz = elementType.toClass();
 		if (String.class.isAssignableFrom(elementType.resolve(clazz))) {
 			return false;
 		}
@@ -121,11 +125,11 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 			return true;
 		}
 		if (!logger.isDebugEnabled()) {
-			return getObjectMapper().canSerialize(clazz);
+			return mapper.canSerialize(clazz);
 		}
 		else {
 			AtomicReference<Throwable> causeRef = new AtomicReference<>();
-			if (getObjectMapper().canSerialize(clazz, causeRef)) {
+			if (mapper.canSerialize(clazz, causeRef)) {
 				return true;
 			}
 			logWarningIfNecessary(clazz, causeRef.get());
@@ -150,10 +154,14 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 			byte[] separator = getStreamingMediaTypeSeparator(mimeType);
 			if (separator != null) { // streaming
 				try {
-					ObjectWriter writer = createObjectWriter(elementType, mimeType, null, hints);
+					ObjectMapper mapper = selectObjectMapper(elementType, mimeType);
+					if (mapper == null) {
+						throw new IllegalStateException("No ObjectMapper for " + elementType);
+					}
+					ObjectWriter writer = createObjectWriter(mapper, elementType, mimeType, null, hints);
 					ByteArrayBuilder byteBuilder = new ByteArrayBuilder(writer.getFactory()._getBufferRecycler());
 					JsonEncoding encoding = getJsonEncoding(mimeType);
-					JsonGenerator generator = getObjectMapper().getFactory().createGenerator(byteBuilder, encoding);
+					JsonGenerator generator = mapper.getFactory().createGenerator(byteBuilder, encoding);
 					SequenceWriter sequenceWriter = writer.writeValues(generator);
 
 					return Flux.from(inputStream)
@@ -188,6 +196,10 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 	public DataBuffer encodeValue(Object value, DataBufferFactory bufferFactory,
 			ResolvableType valueType, @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
 
+		ObjectMapper mapper = selectObjectMapper(valueType, mimeType);
+		if (mapper == null) {
+			throw new IllegalStateException("No ObjectMapper for " + valueType);
+		}
 		Class<?> jsonView = null;
 		FilterProvider filters = null;
 		if (value instanceof MappingJacksonValue) {
@@ -196,7 +208,7 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 			jsonView = container.getSerializationView();
 			filters = container.getFilters();
 		}
-		ObjectWriter writer = createObjectWriter(valueType, mimeType, jsonView, hints);
+		ObjectWriter writer = createObjectWriter(mapper, valueType, mimeType, jsonView, hints);
 		if (filters != null) {
 			writer = writer.with(filters);
 		}
@@ -206,7 +218,7 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 
 			logValue(hints, value);
 
-			try (JsonGenerator generator = getObjectMapper().getFactory().createGenerator(byteBuilder, encoding)) {
+			try (JsonGenerator generator = mapper.getFactory().createGenerator(byteBuilder, encoding)) {
 				writer.writeValue(generator, value);
 				generator.flush();
 			}
@@ -282,20 +294,18 @@ public abstract class AbstractJackson2Encoder extends Jackson2CodecSupport imple
 		}
 	}
 
-	private ObjectWriter createObjectWriter(ResolvableType valueType, @Nullable MimeType mimeType,
+	private ObjectWriter createObjectWriter(
+			ObjectMapper mapper, ResolvableType valueType, @Nullable MimeType mimeType,
 			@Nullable Class<?> jsonView, @Nullable Map<String, Object> hints) {
 
 		JavaType javaType = getJavaType(valueType.getType(), null);
 		if (jsonView == null && hints != null) {
 			jsonView = (Class<?>) hints.get(Jackson2CodecSupport.JSON_VIEW_HINT);
 		}
-		ObjectWriter writer = (jsonView != null ?
+		ObjectWriter writer = (jsonView != null ? mapper.writerWithView(jsonView) : mapper.writer());
-				getObjectMapper().writerWithView(jsonView) : getObjectMapper().writer());
-
 		if (javaType.isContainerType()) {
 			writer = writer.forType(javaType);
 		}
-
 		return customizeWriter(writer, mimeType, valueType, hints);
 	}
 

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

@@ -21,8 +21,10 @@ import java.lang.reflect.Type;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Consumer;
 
 import com.fasterxml.jackson.annotation.JsonView;
 import com.fasterxml.jackson.databind.JavaType;
@@ -40,6 +42,7 @@ import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
 import org.springframework.util.MimeType;
 import org.springframework.util.ObjectUtils;
 
@@ -80,7 +83,10 @@ public abstract class Jackson2CodecSupport {
 
 	protected final Log logger = HttpLogging.forLogName(getClass());
 
-	private final ObjectMapper objectMapper;
+	private final ObjectMapper defaultObjectMapper;
+
+	@Nullable
+	private Map<Class<?>, Map<MimeType, ObjectMapper>> objectMapperRegistrations;
 
 	private final List<MimeType> mimeTypes;
 
@@ -90,14 +96,60 @@ public abstract class Jackson2CodecSupport {
 	 */
 	protected Jackson2CodecSupport(ObjectMapper objectMapper, MimeType... mimeTypes) {
 		Assert.notNull(objectMapper, "ObjectMapper must not be null");
-		this.objectMapper = objectMapper;
+		this.defaultObjectMapper = objectMapper;
 		this.mimeTypes = !ObjectUtils.isEmpty(mimeTypes) ?
 				Collections.unmodifiableList(Arrays.asList(mimeTypes)) : DEFAULT_MIME_TYPES;
 	}
 
 
 	public ObjectMapper getObjectMapper() {
-		return this.objectMapper;
+		return this.defaultObjectMapper;
+	}
+
+	/**
+	 * Configure the {@link ObjectMapper} instances to use for the given
+	 * {@link Class}. This is useful when you want to deviate from the
+	 * {@link #getObjectMapper() default} ObjectMapper or have the
+	 * {@code ObjectMapper} vary by {@code MediaType}.
+	 * <p><strong>Note:</strong> Use of this method effectively turns off use of
+	 * the default {@link #getObjectMapper() ObjectMapper} and supported
+	 * {@link #getMimeTypes() MimeTypes} for the given class. Therefore it is
+	 * important for the mappings configured here to
+	 * {@link MediaType#includes(MediaType) include} every MediaType that must
+	 * be supported for the given class.
+	 * @param clazz the type of Object to register ObjectMapper instances for
+	 * @param registrar a consumer to populate or otherwise update the
+	 * MediaType-to-ObjectMapper associations for the given Class
+	 * @since 5.3.4
+	 */
+	public void registerObjectMappersForType(Class<?> clazz, Consumer<Map<MimeType, ObjectMapper>> registrar) {
+		if (this.objectMapperRegistrations == null) {
+			this.objectMapperRegistrations = new LinkedHashMap<>();
+		}
+		Map<MimeType, ObjectMapper> registrations =
+				this.objectMapperRegistrations.computeIfAbsent(clazz, c -> new LinkedHashMap<>());
+		registrar.accept(registrations);
+	}
+
+	/**
+	 * Return ObjectMapper registrations for the given class, if any.
+	 * @param clazz the class to look up for registrations for
+	 * @return a map with registered MediaType-to-ObjectMapper registrations,
+	 * or empty if in case of no registrations for the given class.
+	 * @since 5.3.4
+	 */
+	@Nullable
+	public Map<MimeType, ObjectMapper> getObjectMappersForType(Class<?> clazz) {
+		for (Map.Entry<Class<?>, Map<MimeType, ObjectMapper>> entry : getObjectMapperRegistrations().entrySet()) {
+			if (entry.getKey().isAssignableFrom(clazz)) {
+				return entry.getValue();
+			}
+		}
+		return Collections.emptyMap();
+	}
+
+	private Map<Class<?>, Map<MimeType, ObjectMapper>> getObjectMapperRegistrations() {
+		return (this.objectMapperRegistrations != null ? this.objectMapperRegistrations : Collections.emptyMap());
 	}
 
 	/**
@@ -140,7 +192,7 @@ public abstract class Jackson2CodecSupport {
 	}
 
 	protected JavaType getJavaType(Type type, @Nullable Class<?> contextClass) {
-		return this.objectMapper.constructType(GenericTypeResolver.resolveType(type, contextClass));
+		return this.defaultObjectMapper.constructType(GenericTypeResolver.resolveType(type, contextClass));
 	}
 
 	protected Map<String, Object> getHints(ResolvableType resolvableType) {
@@ -173,4 +225,31 @@ public abstract class Jackson2CodecSupport {
 	@Nullable
 	protected abstract <A extends Annotation> A getAnnotation(MethodParameter parameter, Class<A> annotType);
 
+	/**
+	 * Select an ObjectMapper to use, either the main ObjectMapper or another
+	 * if the handling for the given Class has been customized through
+	 * {@link #registerObjectMappersForType(Class, Consumer)}.
+	 * @since 5.3.4
+	 */
+	@Nullable
+	protected ObjectMapper selectObjectMapper(ResolvableType targetType, @Nullable MimeType targetMimeType) {
+		if (targetMimeType == null || CollectionUtils.isEmpty(this.objectMapperRegistrations)) {
+			return this.defaultObjectMapper;
+		}
+		Class<?> targetClass = targetType.toClass();
+		for (Map.Entry<Class<?>, Map<MimeType, ObjectMapper>> typeEntry : getObjectMapperRegistrations().entrySet()) {
+			if (typeEntry.getKey().isAssignableFrom(targetClass)) {
+				for (Map.Entry<MimeType, ObjectMapper> objectMapperEntry : typeEntry.getValue().entrySet()) {
+					if (objectMapperEntry.getKey().includes(targetMimeType)) {
+						return objectMapperEntry.getValue();
+					}
+				}
+				// No matching registrations
+				return null;
+			}
+		}
+		// No registrations
+		return this.defaultObjectMapper;
+	}
+
 }

spring-web/src/test/java/org/springframework/http/codec/json/Jackson2JsonDecoderTests.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.
@@ -92,6 +92,28 @@ public class Jackson2JsonDecoderTests extends AbstractDecoderTests<Jackson2JsonD
 				new MediaType("application", "json", StandardCharsets.ISO_8859_1))).isTrue();
 	}
 
+	@Test
+	public void canDecodeWithObjectMapperRegistrationForType() {
+				MediaType halJsonMediaType = MediaType.parseMediaType("application/hal+json");
+		MediaType halFormsJsonMediaType = MediaType.parseMediaType("application/prs.hal-forms+json");
+
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), halJsonMediaType)).isTrue();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), MediaType.APPLICATION_JSON)).isTrue();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), halFormsJsonMediaType)).isTrue();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Map.class), MediaType.APPLICATION_JSON)).isTrue();
+
+		decoder.registerObjectMappersForType(Pojo.class, map -> {
+			map.put(halJsonMediaType, new ObjectMapper());
+			map.put(MediaType.APPLICATION_JSON, new ObjectMapper());
+		});
+
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), halJsonMediaType)).isTrue();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), MediaType.APPLICATION_JSON)).isTrue();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Pojo.class), halFormsJsonMediaType)).isFalse();
+		assertThat(decoder.canDecode(ResolvableType.forClass(Map.class), MediaType.APPLICATION_JSON)).isTrue();
+
+	}
+
 	@Test  // SPR-15866
 	public void canDecodeWithProvidedMimeType() {
 		MimeType textJavascript = new MimeType("text", "javascript", StandardCharsets.UTF_8);