Fix issue with @RequestBody args that are type vars

The change to support generic @RequestBody arguments introduced in
3.2 M2 also introduced a regression in reading arguments that are
type variables. This change fixes the issue.

Issue: SPR-9964

spring-web/src/main/java/org/springframework/http/converter/GenericHttpMessageConverter.java

@@ -27,6 +27,7 @@ import org.springframework.http.MediaType;
  * request into a target object of a specified generic type.
  *
  * @author Arjen Poutsma
+ * @author Rossen Stoyanchev
  * @since 3.2
  *
  * @see org.springframework.core.ParameterizedTypeReference
@@ -36,11 +37,13 @@ public interface GenericHttpMessageConverter<T> extends HttpMessageConverter<T>
 	/**
 	 * Indicates whether the given type can be read by this converter.
 	 * @param type the type to test for readability
+	 * @param contextClass a context class for the target type, for example a class
+	 * in which the target type appears in a method signature, can be {@code null}
 	 * @param mediaType the media type to read, can be {@code null} if not specified.
 	 * Typically the value of a {@code Content-Type} header.
 	 * @return {@code true} if readable; {@code false} otherwise
 	 */
-	boolean canRead(Type type, MediaType mediaType);
+	boolean canRead(Type type, Class<?> contextClass, MediaType mediaType);
 
 	/**
 	 * Read an object of the given type form the given input message, and returns it.
@@ -48,12 +51,14 @@ public interface GenericHttpMessageConverter<T> extends HttpMessageConverter<T>
 	 * been passed to the {@link #canRead canRead} method of this interface,
 	 * which must have returned {@code true}.
 	 * @param type the type of the target object
+	 * @param contextClass a context class for the target type, for example a class
+	 * in which the target type appears in a method signature, can be {@code null}
 	 * @param inputMessage the HTTP input message to read from
 	 * @return the converted object
 	 * @throws IOException in case of I/O errors
 	 * @throws HttpMessageNotReadableException in case of conversion errors
 	 */
-	T read(Type type, HttpInputMessage inputMessage)
+	T read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException;
 
 }

spring-web/src/main/java/org/springframework/http/converter/json/MappingJackson2HttpMessageConverter.java

@@ -128,11 +128,11 @@ public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConv
 
 	@Override
 	public boolean canRead(Class<?> clazz, MediaType mediaType) {
-		return canRead((Type) clazz, mediaType);
+		return canRead((Type) clazz, null, mediaType);
 	}
 
-	public boolean canRead(Type type, MediaType mediaType) {
-		JavaType javaType = getJavaType(type);
+	public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
+		JavaType javaType = getJavaType(type, contextClass);
 		return (this.objectMapper.canDeserialize(javaType) && canRead(mediaType));
 	}
 
@@ -151,14 +151,14 @@ public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConv
 	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		JavaType javaType = getJavaType(clazz);
+		JavaType javaType = getJavaType(clazz, null);
 		return readJavaType(javaType, inputMessage);
 	}
 
-	public Object read(Type type, HttpInputMessage inputMessage)
+	public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		JavaType javaType = getJavaType(type);
+		JavaType javaType = getJavaType(type, contextClass);
 		return readJavaType(javaType, inputMessage);
 	}
 
@@ -197,10 +197,10 @@ public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConv
 		}
 	}
 
-
 	/**
-	 * Return the Jackson {@link JavaType} for the specified type.
-	 * <p>The default implementation returns {@link ObjectMapper#constructType(java.lang.reflect.Type)},
+	 * Return the Jackson {@link JavaType} for the specified type and context class.
+	 * <p>The default implementation returns {@link ObjectMapper#constructType(java.lang.reflect.Type)}
+	 * or {@code ObjectMapper.getTypeFactory().constructType(type, contextClass)},
 	 * but this can be overridden in subclasses, to allow for custom generic collection handling.
 	 * For instance:
 	 * <pre class="code">
@@ -213,10 +213,15 @@ public class MappingJackson2HttpMessageConverter extends AbstractHttpMessageConv
 	 * }
 	 * </pre>
 	 * @param type the type to return the java type for
+	 * @param contextClass a context class for the target type, for example a class
+	 * in which the target type appears in a method signature, can be {@code null}
+	 * signature, can be {@code null}
 	 * @return the java type
 	 */
-	protected JavaType getJavaType(Type type) {
-		return this.objectMapper.constructType(type);
+	protected JavaType getJavaType(Type type, Class<?> contextClass) {
+		return (contextClass != null) ?
+			this.objectMapper.getTypeFactory().constructType(type, contextClass) :
+			this.objectMapper.constructType(type);
 	}
 
 	/**

spring-web/src/main/java/org/springframework/http/converter/json/MappingJacksonHttpMessageConverter.java

@@ -128,11 +128,11 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 
 	@Override
 	public boolean canRead(Class<?> clazz, MediaType mediaType) {
-		return canRead((Type) clazz, mediaType);
+		return canRead((Type) clazz, null, mediaType);
 	}
 
-	public boolean canRead(Type type, MediaType mediaType) {
-		JavaType javaType = getJavaType(type);
+	public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
+		JavaType javaType = getJavaType(type, contextClass);
 		return (this.objectMapper.canDeserialize(javaType) && canRead(mediaType));
 	}
 
@@ -151,14 +151,14 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		JavaType javaType = getJavaType(clazz);
+		JavaType javaType = getJavaType(clazz, null);
 		return readJavaType(javaType, inputMessage);
 	}
 
-	public Object read(Type type, HttpInputMessage inputMessage)
+	public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		JavaType javaType = getJavaType(type);
+		JavaType javaType = getJavaType(type, contextClass);
 		return readJavaType(javaType, inputMessage);
 	}
 
@@ -196,10 +196,10 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 		}
 	}
 
-
 	/**
-	 * Return the Jackson {@link JavaType} for the specified type.
-	 * <p>The default implementation returns {@link TypeFactory#type(java.lang.reflect.Type)},
+	 * Return the Jackson {@link JavaType} for the specified type and context class.
+	 * <p>The default implementation returns {@link TypeFactory#type(java.lang.reflect.Type)}
+	 * or {@code TypeFactory.type(type, TypeFactory.type(contextClass))},
 	 * but this can be overridden in subclasses, to allow for custom generic collection handling.
 	 * For instance:
 	 * <pre class="code">
@@ -212,10 +212,14 @@ public class MappingJacksonHttpMessageConverter extends AbstractHttpMessageConve
 	 * }
 	 * </pre>
 	 * @param type the type to return the java type for
+	 * @param contextClass a context class for the target type, for example a class
+	 * in which the target type appears in a method signature, can be {@code null}
 	 * @return the java type
 	 */
-	protected JavaType getJavaType(Type type) {
-		return TypeFactory.type(type);
+	protected JavaType getJavaType(Type type, Class<?> contextClass) {
+		return (contextClass != null) ?
+			TypeFactory.type(type, TypeFactory.type(contextClass)) :
+			TypeFactory.type(type);
 	}
 
 	/**

spring-web/src/main/java/org/springframework/http/converter/xml/Jaxb2CollectionHttpMessageConverter.java

@@ -74,7 +74,7 @@ public class Jaxb2CollectionHttpMessageConverter<T extends Collection>
 	 * {@link Collection} where the generic type is a JAXB type annotated with
 	 * {@link XmlRootElement} or {@link XmlType}.
 	 */
-	public boolean canRead(Type type, MediaType mediaType) {
+	public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
 		if (!(type instanceof ParameterizedType)) {
 			return false;
 		}
@@ -119,7 +119,9 @@ public class Jaxb2CollectionHttpMessageConverter<T extends Collection>
 		throw new UnsupportedOperationException();
 	}
 
-	public T read(Type type, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
+	public T read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
+			throws IOException, HttpMessageNotReadableException {
+
 		ParameterizedType parameterizedType = (ParameterizedType) type;
 		T result = createCollection((Class<?>) parameterizedType.getRawType());
 		Class<?> elementClass = (Class<?>) parameterizedType.getActualTypeArguments()[0];

spring-web/src/main/java/org/springframework/web/client/HttpMessageConverterExtractor.java

@@ -86,12 +86,12 @@ public class HttpMessageConverterExtractor<T> implements ResponseExtractor<T> {
 		for (HttpMessageConverter messageConverter : this.messageConverters) {
 			if (messageConverter instanceof GenericHttpMessageConverter) {
 				GenericHttpMessageConverter genericMessageConverter = (GenericHttpMessageConverter) messageConverter;
-				if (genericMessageConverter.canRead(this.responseType, contentType)) {
+				if (genericMessageConverter.canRead(this.responseType, null, contentType)) {
 					if (logger.isDebugEnabled()) {
 						logger.debug("Reading [" + this.responseType + "] as \"" +
 								contentType + "\" using [" + messageConverter + "]");
 					}
-					return (T) genericMessageConverter.read(this.responseType, response);
+					return (T) genericMessageConverter.read(this.responseType, null, response);
 				}
 			}
 			if (this.responseClass != null) {

spring-web/src/main/java/org/springframework/web/client/RestTemplate.java

@@ -553,20 +553,17 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 				}
 
 				List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>();
-				for (HttpMessageConverter<?> messageConverter : getMessageConverters()) {
+				for (HttpMessageConverter<?> converter : getMessageConverters()) {
 					if (responseClass != null) {
-						if (messageConverter.canRead(responseClass, null)) {
-							allSupportedMediaTypes
-									.addAll(getSupportedMediaTypes(messageConverter));
+						if (converter.canRead(responseClass, null)) {
+							allSupportedMediaTypes.addAll(getSupportedMediaTypes(converter));
 						}
 					}
-					else if (messageConverter instanceof GenericHttpMessageConverter) {
+					else if (converter instanceof GenericHttpMessageConverter) {
 
-						GenericHttpMessageConverter genericMessageConverter =
-								(GenericHttpMessageConverter) messageConverter;
-						if (genericMessageConverter.canRead(responseType, null)) {
-							allSupportedMediaTypes
-									.addAll(getSupportedMediaTypes(messageConverter));
+						GenericHttpMessageConverter genericConverter = (GenericHttpMessageConverter) converter;
+						if (genericConverter.canRead(responseType, null, null)) {
+							allSupportedMediaTypes.addAll(getSupportedMediaTypes(converter));
 						}
 					}