Backported JSON converter alignment (supports method, exception messages)

Includes deprecation of getTypeToken method in GsonHttpMessageConverter.

Issue: SPR-15381

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -29,6 +29,7 @@ import org.springframework.http.StreamingHttpOutputMessage;
  * Abstract base class for most {@link GenericHttpMessageConverter} implementations.
  *
  * @author Sebastien Deleuze
+ * @author Juergen Hoeller
  * @since 4.2
  */
 public abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHttpMessageConverter<T>
@@ -58,9 +59,14 @@ public abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHtt
 	}
 
 
+	@Override
+	protected boolean supports(Class<?> clazz) {
+		return true;
+	}
+
 	@Override
 	public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
-		return canRead(contextClass, mediaType);
+		return (type instanceof Class ? canRead((Class<?>) type, mediaType) : canRead(mediaType));
 	}
 
 	@Override
@@ -102,7 +108,6 @@ public abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHtt
 		}
 	}
 
-
 	@Override
 	protected void writeInternal(T t, HttpOutputMessage outputMessage)
 			throws IOException, HttpMessageNotWritableException {
@@ -113,7 +118,7 @@ public abstract class AbstractGenericHttpMessageConverter<T> extends AbstractHtt
 	/**
 	 * Abstract template method that writes the actual body. Invoked from {@link #write}.
 	 * @param t the object to write to the output message
-	 * @param type the type of object to write, can be {@code null} if not specified.
+	 * @param type the type of object to write (may be {@code null})
 	 * @param outputMessage the HTTP output message to write to
 	 * @throws IOException in case of I/O errors
 	 * @throws HttpMessageNotWritableException in case of conversion errors

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

@@ -51,8 +51,24 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 
 
 	@Override
-	protected boolean supports(Class<?> clazz) {
-		// should not be called as we override canRead/canWrite
+	@SuppressWarnings("unchecked")
+	protected MediaType getDefaultContentType(Object object) {
+		if (jafPresent) {
+			if(object instanceof ResourceRegion) {
+				return ActivationMediaTypeFactory.getMediaType(((ResourceRegion) object).getResource());
+			}
+			else {
+				Collection<ResourceRegion> regions = (Collection<ResourceRegion>) object;
+				if(regions.size() > 0) {
+					return ActivationMediaTypeFactory.getMediaType(regions.iterator().next().getResource());
+				}
+			}
+		}
+		return MediaType.APPLICATION_OCTET_STREAM;
+	}
+
+	@Override
+	public boolean canRead(Class<?> clazz, MediaType mediaType) {
 		return false;
 	}
 
@@ -65,31 +81,14 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 	public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		return null;
+		throw new UnsupportedOperationException();
 	}
 
 	@Override
 	protected ResourceRegion readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		return null;
-	}
-
-	@Override
-	@SuppressWarnings("unchecked")
-	protected MediaType getDefaultContentType(Object object) {
-		if (jafPresent) {
-			if(object instanceof ResourceRegion) {
-				return ActivationMediaTypeFactory.getMediaType(((ResourceRegion) object).getResource());
-			}
-			else {
-				Collection<ResourceRegion> regions = (Collection<ResourceRegion>) object;
-				if(regions.size() > 0) {
-					return ActivationMediaTypeFactory.getMediaType(regions.iterator().next().getResource());
-				}
-			}
-		}
-		return MediaType.APPLICATION_OCTET_STREAM;
+		throw new UnsupportedOperationException();
 	}
 
 	@Override
@@ -100,7 +99,7 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 	@Override
 	public boolean canWrite(Type type, Class<?> clazz, MediaType mediaType) {
 		if (!(type instanceof ParameterizedType)) {
-			return ResourceRegion.class.isAssignableFrom((Class) type);
+			return ResourceRegion.class.isAssignableFrom((Class<?>) type);
 		}
 		ParameterizedType parameterizedType = (ParameterizedType) type;
 		if (!(parameterizedType.getRawType() instanceof Class)) {
@@ -140,6 +139,7 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 		}
 	}
 
+
 	protected void writeResourceRegion(ResourceRegion region, HttpOutputMessage outputMessage) throws IOException {
 		Assert.notNull(region, "ResourceRegion must not be null");
 		HttpHeaders responseHeaders = outputMessage.getHeaders();
@@ -197,8 +197,6 @@ public class ResourceRegionHttpMessageConverter extends AbstractGenericHttpMessa
 		print(out, "--" + boundaryString + "--");
 	}
 
-
-
 	private static void println(OutputStream os) throws IOException {
 		os.write('\r');
 		os.write('\n');

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -203,12 +203,6 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 		}
 	}
 
-	@Override
-	protected boolean supports(Class<?> clazz) {
-		// should not be called, since we override canRead/Write instead
-		throw new UnsupportedOperationException();
-	}
-
 	@Override
 	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
@@ -237,7 +231,7 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 			return this.objectMapper.readValue(inputMessage.getBody(), javaType);
 		}
 		catch (IOException ex) {
-			throw new HttpMessageNotReadableException("Could not read document: " + ex.getMessage(), ex);
+			throw new HttpMessageNotReadableException("Could not read JSON document: " + ex.getMessage(), ex);
 		}
 	}
 
@@ -289,7 +283,7 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 
 		}
 		catch (JsonProcessingException ex) {
-			throw new HttpMessageNotWritableException("Could not write content: " + ex.getMessage(), ex);
+			throw new HttpMessageNotWritableException("Could not write JSON document: " + ex.getMessage(), ex);
 		}
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -114,34 +114,20 @@ public class GsonHttpMessageConverter extends AbstractGenericHttpMessageConverte
 
 
 	@Override
-	public boolean canRead(Class<?> clazz, MediaType mediaType) {
-		return canRead(mediaType);
-	}
-
-	@Override
-	public boolean canWrite(Class<?> clazz, MediaType mediaType) {
-		return canWrite(mediaType);
-	}
-
-	@Override
-	protected boolean supports(Class<?> clazz) {
-		// should not be called, since we override canRead/Write instead
-		throw new UnsupportedOperationException();
-	}
-
-	@Override
-	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
+	@SuppressWarnings("deprecation")
+	public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		TypeToken<?> token = getTypeToken(clazz);
+		TypeToken<?> token = getTypeToken(type);
 		return readTypeToken(token, inputMessage);
 	}
 
 	@Override
-	public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage)
+	@SuppressWarnings("deprecation")
+	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
 
-		TypeToken<?> token = getTypeToken(type);
+		TypeToken<?> token = getTypeToken(clazz);
 		return readTypeToken(token, inputMessage);
 	}
 
@@ -162,7 +148,9 @@ public class GsonHttpMessageConverter extends AbstractGenericHttpMessageConverte
 	 * </pre>
 	 * @param type the type for which to return the TypeToken
 	 * @return the type token
+	 * @deprecated as of Spring Framework 4.3.8, in favor of signature-based resolution
 	 */
+	@Deprecated
 	protected TypeToken<?> getTypeToken(Type type) {
 		return TypeToken.get(type);
 	}
@@ -173,7 +161,7 @@ public class GsonHttpMessageConverter extends AbstractGenericHttpMessageConverte
 			return this.gson.fromJson(json, token.getType());
 		}
 		catch (JsonParseException ex) {
-			throw new HttpMessageNotReadableException("Could not read JSON: " + ex.getMessage(), ex);
+			throw new HttpMessageNotReadableException("Could not read JSON document: " + ex.getMessage(), ex);
 		}
 	}
 
@@ -203,7 +191,7 @@ public class GsonHttpMessageConverter extends AbstractGenericHttpMessageConverte
 			writer.close();
 		}
 		catch (JsonIOException ex) {
-			throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getMessage(), ex);
+			throw new HttpMessageNotWritableException("Could not write JSON document: " + ex.getMessage(), ex);
 		}
 	}