relaxed generic Class declaration in HttpMessageConverter's canRead/canWrite/read signatures (SPR-6848)

Author: jhoeller

org.springframework.web/src/main/java/org/springframework/http/converter/AbstractHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -34,11 +34,12 @@
 /**
  * Abstract base class for most {@link HttpMessageConverter} implementations.
  *
- * <p>This base class adds support for setting supported {@code MediaTypes}, through the {@link
- * #setSupportedMediaTypes(List) supportedMediaTypes} bean property. It also adds support for {@code Content-Type} and
- * {@code Content-Length} when writing to output messages.
+ * <p>This base class adds support for setting supported {@code MediaTypes}, through the
+ * {@link #setSupportedMediaTypes(List) supportedMediaTypes} bean property. It also adds
+ * support for {@code Content-Type} and {@code Content-Length} when writing to output messages.
  *
  * @author Arjen Poutsma
+ * @author Juergen Hoeller
  * @since 3.0
  */
 public abstract class AbstractHttpMessageConverter<T> implements HttpMessageConverter<T> {
@@ -48,17 +49,16 @@ public abstract class AbstractHttpMessageConverter<T> implements HttpMessageConv
 
 	private List<MediaType> supportedMediaTypes = Collections.emptyList();
 
+
 	/**
 	 * Construct an {@code AbstractHttpMessageConverter} with no supported media types.
-	 *
 	 * @see #setSupportedMediaTypes
 	 */
 	protected AbstractHttpMessageConverter() {
 	}
 
 	/**
 	 * Construct an {@code AbstractHttpMessageConverter} with one supported media type.
-	 *
 	 * @param supportedMediaType the supported media type
 	 */
 	protected AbstractHttpMessageConverter(MediaType supportedMediaType) {
@@ -67,14 +67,16 @@ protected AbstractHttpMessageConverter(MediaType supportedMediaType) {
 
 	/**
 	 * Construct an {@code AbstractHttpMessageConverter} with multiple supported media type.
-	 *
 	 * @param supportedMediaTypes the supported media types
 	 */
 	protected AbstractHttpMessageConverter(MediaType... supportedMediaTypes) {
 		setSupportedMediaTypes(Arrays.asList(supportedMediaTypes));
 	}
 
-	/** Set the list of {@link MediaType} objects supported by this converter. */
+
+	/**
+	 * Set the list of {@link MediaType} objects supported by this converter.
+	 */
 	public void setSupportedMediaTypes(List<MediaType> supportedMediaTypes) {
 		Assert.notEmpty(supportedMediaTypes, "'supportedMediaTypes' must not be empty");
 		this.supportedMediaTypes = new ArrayList<MediaType>(supportedMediaTypes);
@@ -84,21 +86,20 @@ public List<MediaType> getSupportedMediaTypes() {
 		return Collections.unmodifiableList(this.supportedMediaTypes);
 	}
 
+
 	/**
 	 * {@inheritDoc}
-	 *
-	 * <p>This implementation checks if the given class is {@linkplain #supports(Class) supported}, and if the {@linkplain
-	 * #getSupportedMediaTypes() supported media types} {@linkplain MediaType#includes(MediaType) include} the given media
-	 * type.
+	 * <p>This implementation checks if the given class is {@linkplain #supports(Class) supported},
+	 * and if the {@linkplain #getSupportedMediaTypes() supported media types}
+	 * {@linkplain MediaType#includes(MediaType) include} the given media type.
 	 */
 	public boolean canRead(Class<?> clazz, MediaType mediaType) {
 		return supports(clazz) && canRead(mediaType);
 	}
 
 	/**
-	 * Returns true if any of the {@linkplain #setSupportedMediaTypes(List) supported media types} include the given media
-	 * type.
-	 *
+	 * Returns true if any of the {@linkplain #setSupportedMediaTypes(List) supported media types}
+	 * include the given media type.
 	 * @param mediaType the media type
 	 * @return true if the supported media types include the media type, or if the media type is {@code null}
 	 */
@@ -116,10 +117,9 @@ protected boolean canRead(MediaType mediaType) {
 
 	/**
 	 * {@inheritDoc}
-	 *
-	 * <p>This implementation checks if the given class is {@linkplain #supports(Class) supported}, and if the {@linkplain
-	 * #getSupportedMediaTypes() supported media types} {@linkplain MediaType#includes(MediaType) include} the given media
-	 * type.
+	 * <p>This implementation checks if the given class is {@linkplain #supports(Class) supported},
+	 * and if the {@linkplain #getSupportedMediaTypes() supported media types}
+	 * {@linkplain MediaType#includes(MediaType) include} the given media type.
 	 */
 	public boolean canWrite(Class<?> clazz, MediaType mediaType) {
 		return supports(clazz) && canWrite(mediaType);
@@ -128,7 +128,6 @@ public boolean canWrite(Class<?> clazz, MediaType mediaType) {
 	/**
 	 * Returns true if the given media type includes any of the
 	 * {@linkplain #setSupportedMediaTypes(List) supported media types}.
-	 *
 	 * @param mediaType the media type
 	 * @return true if the supported media types include the media type, or if the media type is {@code null}
 	 */
@@ -144,45 +143,24 @@ protected boolean canWrite(MediaType mediaType) {
 		return false;
 	}
 
-	/**
-	 * Indicates whether the given class is supported by this converter.
-	 *
-	 * @param clazz the class to test for support
-	 * @return <code>true</code> if supported; <code>false</code> otherwise
-	 */
-	protected abstract boolean supports(Class<?> clazz);
-
 	/**
 	 * {@inheritDoc}
-	 *
-	 * <p>This implementation simple delegates to {@link #readInternal(Class, HttpInputMessage)}. Future implementations
-	 * might add some default behavior, however.
+	 * <p>This implementation simple delegates to {@link #readInternal(Class, HttpInputMessage)}.
+	 * Future implementations might add some default behavior, however.
 	 */
-	public final T read(Class<T> clazz, HttpInputMessage inputMessage) throws IOException {
+	public final T read(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException {
 		return readInternal(clazz, inputMessage);
 	}
 
-	/**
-	 * Abstract template method that reads the actualy object. Invoked from {@link #read(Class, HttpInputMessage)}.
-	 *
-	 * @param clazz the type of object to return
-	 * @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
-	 */
-	protected abstract T readInternal(Class<T> clazz, HttpInputMessage inputMessage)
-			throws IOException, HttpMessageNotReadableException;
-
 	/**
 	 * {@inheritDoc}
-	 *
-	 * <p>This implementation delegates to {@link #getDefaultContentType(Object)} if a content type was not provided, calls
-	 * {@link #getContentLength}, and sets the corresponding headers on the output message. It then calls {@link
-	 * #writeInternal}.
+	 * <p>This implementation delegates to {@link #getDefaultContentType(Object)} if a content
+	 * type was not provided, calls {@link #getContentLength}, and sets the corresponding headers
+	 * on the output message. It then calls {@link #writeInternal}.
 	 */
 	public final void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
 			throws IOException, HttpMessageNotWritableException {
+
 		HttpHeaders headers = outputMessage.getHeaders();
 		if (contentType == null || contentType.isWildcardType() || contentType.isWildcardSubtype()) {
 			contentType = getDefaultContentType(t);
@@ -199,12 +177,11 @@ public final void write(T t, MediaType contentType, HttpOutputMessage outputMess
 	}
 
 	/**
-	 * Returns the default content type for the given type. Called when {@link #write} is invoked without a specified
-	 * content type parameter.
-	 *
-	 * <p>By default, this returns the first element of the {@link #setSupportedMediaTypes(List) supportedMediaTypes}
-	 * property, if any. Can be overriden in subclasses.
-	 *
+	 * Returns the default content type for the given type. Called when {@link #write}
+	 * is invoked without a specified content type parameter.
+	 * <p>By default, this returns the first element of the
+	 * {@link #setSupportedMediaTypes(List) supportedMediaTypes} property, if any.
+	 * Can be overridden in subclasses.
 	 * @param t the type to return the content type for
 	 * @return the content type, or <code>null</code> if not known
 	 */
@@ -215,20 +192,36 @@ protected MediaType getDefaultContentType(T t) {
 
 	/**
 	 * Returns the content length for the given type.
-	 *
-	 * <p>By default, this returns {@code null}, meaning that the content length is unknown. Can be overriden in
-	 * subclasses.
-	 *
+	 * <p>By default, this returns {@code null}, meaning that the content length is unknown.
+	 * Can be overridden in subclasses.
 	 * @param t the type to return the content length for
 	 * @return the content length, or {@code null} if not known
 	 */
 	protected Long getContentLength(T t, MediaType contentType) {
 		return null;
 	}
 
+
+	/**
+	 * Indicates whether the given class is supported by this converter.
+	 * @param clazz the class to test for support
+	 * @return <code>true</code> if supported; <code>false</code> otherwise
+	 */
+	protected abstract boolean supports(Class<?> clazz);
+
+	/**
+	 * Abstract template method that reads the actualy object. Invoked from {@link #read}.
+	 * @param clazz the type of object to return
+	 * @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
+	 */
+	protected abstract T readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage)
+			throws IOException, HttpMessageNotReadableException;
+
 	/**
 	 * Abstract template method that writes the actual body. Invoked from {@link #write}.
-	 *
 	 * @param t the object to write to the output message
 	 * @param outputMessage the message to write to
 	 * @throws IOException in case of I/O errors

org.springframework.web/src/main/java/org/springframework/http/converter/BufferedImageHttpMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2010 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.
@@ -62,37 +62,27 @@
  */
 public class BufferedImageHttpMessageConverter implements HttpMessageConverter<BufferedImage> {
 
-	private List<MediaType> readableMediaTypes = new ArrayList<MediaType>();
+	private final List<MediaType> readableMediaTypes = new ArrayList<MediaType>();
 
 	private MediaType defaultContentType;
 
 	private File cacheDir;
 
+
 	public BufferedImageHttpMessageConverter() {
 		String[] readerMediaTypes = ImageIO.getReaderMIMETypes();
 		for (String mediaType : readerMediaTypes) {
-			readableMediaTypes.add(MediaType.parseMediaType(mediaType));
+			this.readableMediaTypes.add(MediaType.parseMediaType(mediaType));
 		}
 
 		String[] writerMediaTypes = ImageIO.getWriterMIMETypes();
 		if (writerMediaTypes.length > 0) {
-			defaultContentType = MediaType.parseMediaType(writerMediaTypes[0]);
+			this.defaultContentType = MediaType.parseMediaType(writerMediaTypes[0]);
 		}
 	}
 
-	/**
-	 * Returns the default {@code Content-Type} to be used for writing. Called when {@link #write} is invoked without a
-	 * specified content type parameter.
-	 *
-	 * @return the default content type
-	 */
-	public MediaType getDefaultContentType() {
-		return defaultContentType;
-	}
-
 	/**
 	 * Sets the default {@code Content-Type} to be used for writing.
-	 *
 	 * @throws IllegalArgumentException if the given content type is not supported by the Java Image I/O API
 	 */
 	public void setDefaultContentType(MediaType defaultContentType) {
@@ -106,20 +96,27 @@ public void setDefaultContentType(MediaType defaultContentType) {
 		this.defaultContentType = defaultContentType;
 	}
 
-	/** Sets the cache directory. If this property is set to an existing directory, this converter will cache image data. */
+	/**
+	 * Returns the default {@code Content-Type} to be used for writing.
+	 * Called when {@link #write} is invoked without a specified content type parameter.
+	 */
+	public MediaType getDefaultContentType() {
+		return this.defaultContentType;
+	}
+
+	/**
+	 * Sets the cache directory. If this property is set to an existing directory,
+	 * this converter will cache image data.
+	 */
 	public void setCacheDir(File cacheDir) {
 		Assert.notNull(cacheDir, "'cacheDir' must not be null");
 		Assert.isTrue(cacheDir.isDirectory(), "'cacheDir' is not a directory");
 		this.cacheDir = cacheDir;
 	}
 
+
 	public boolean canRead(Class<?> clazz, MediaType mediaType) {
-		if (BufferedImage.class.equals(clazz)) {
-			return isReadable(mediaType);
-		}
-		else {
-			return false;
-		}
+		return (BufferedImage.class.equals(clazz) && isReadable(mediaType));
 	}
 
 	private boolean isReadable(MediaType mediaType) {
@@ -131,12 +128,7 @@ private boolean isReadable(MediaType mediaType) {
 	}
 
 	public boolean canWrite(Class<?> clazz, MediaType mediaType) {
-		if (BufferedImage.class.equals(clazz)) {
-			return isWritable(mediaType);
-		}
-		else {
-			return false;
-		}
+		return (BufferedImage.class.equals(clazz) && isWritable(mediaType));
 	}
 
 	private boolean isWritable(MediaType mediaType) {
@@ -148,11 +140,12 @@ private boolean isWritable(MediaType mediaType) {
 	}
 
 	public List<MediaType> getSupportedMediaTypes() {
-		return Collections.unmodifiableList(readableMediaTypes);
+		return Collections.unmodifiableList(this.readableMediaTypes);
 	}
 
-	public BufferedImage read(Class<BufferedImage> clazz, HttpInputMessage inputMessage)
+	public BufferedImage read(Class<? extends BufferedImage> clazz, HttpInputMessage inputMessage)
 			throws IOException, HttpMessageNotReadableException {
+
 		ImageInputStream imageInputStream = null;
 		ImageReader imageReader = null;
 		try {
@@ -187,7 +180,7 @@ public BufferedImage read(Class<BufferedImage> clazz, HttpInputMessage inputMess
 	}
 
 	private ImageInputStream createImageInputStream(InputStream is) throws IOException {
-		if (cacheDir != null) {
+		if (this.cacheDir != null) {
 			return new FileCacheImageInputStream(is, cacheDir);
 		}
 		else {
@@ -197,6 +190,7 @@ private ImageInputStream createImageInputStream(InputStream is) throws IOExcepti
 
 	public void write(BufferedImage image, MediaType contentType, HttpOutputMessage outputMessage)
 			throws IOException, HttpMessageNotWritableException {
+
 		if (contentType == null) {
 			contentType = getDefaultContentType();
 		}
@@ -236,27 +230,27 @@ public void write(BufferedImage image, MediaType contentType, HttpOutputMessage
 	}
 
 	private ImageOutputStream createImageOutputStream(OutputStream os) throws IOException {
-		if (cacheDir != null) {
-			return new FileCacheImageOutputStream(os, cacheDir);
+		if (this.cacheDir != null) {
+			return new FileCacheImageOutputStream(os, this.cacheDir);
 		}
 		else {
 			return new MemoryCacheImageOutputStream(os);
 		}
 	}
 
+
 	/**
 	 * Template method that allows for manipulating the {@link ImageReadParam} before it is used to read an image.
-	 *
 	 * <p>Default implementation is empty.
 	 */
 	protected void process(ImageReadParam irp) {
 	}
 
 	/**
 	 * Template method that allows for manipulating the {@link ImageWriteParam} before it is used to write an image.
-	 *
 	 * <p>Default implementation is empty.
 	 */
 	protected void process(ImageWriteParam iwp) {
 	}
+
 }