public interface HttpMessageConverter<T> {        /**      * Indicates whether the given class can be read by this converter.      * @param clazz the class to test for readability      * @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(Class<?> clazz, MediaType mediaType);        /**      * Indicates whether the given class can be written by this converter.      * @param clazz the class to test for writability      * @param mediaType the media type to write, can be {@code null} if not specified.      * Typically the value of an {@code Accept} header.      * @return {@code true} if writable; {@code false} otherwise      */      boolean canWrite(Class<?> clazz, MediaType mediaType);        /**      * Return the list of {@link MediaType} objects supported by this converter.      * @return the list of supported media types      */      List<MediaType> getSupportedMediaTypes();        /**      * Read an object of the given type form the given input message, and returns it.      * @param clazz the type of object to return. This type must have previously been passed to the      * {@link #canRead canRead} method of this interface, which must have returned {@code true}.      * @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(Class<? extends T> clazz, HttpInputMessage inputMessage)              throws IOException, HttpMessageNotReadableException;        /**      * Write an given object to the given output message.      * @param t the object to write to the output message. The type of this object must have previously been      * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}.      * @param contentType the content type to use when writing. May be {@code null} to indicate that the      * default content type of the converter must be used. If not {@code null}, this media type must have      * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have      * returned {@code true}.      * @param outputMessage the message to write to      * @throws IOException in case of I/O errors      * @throws HttpMessageNotWritableException in case of conversion errors      */      void write(T t, MediaType contentType, HttpOutputMessage outputMessage)              throws IOException, HttpMessageNotWritableException;    }

ByteArrayHttpMessageConverter converts byte arrays.    StringHttpMessageConverter converts strings.    ResourceHttpMessageConverter converts to/from org.springframework.core.io.Resource for all media types.    SourceHttpMessageConverter converts to/from a javax.xml.transform.Source.    FormHttpMessageConverter converts form data to/from a MultiValueMap<String, String>.    Jaxb2RootElementHttpMessageConverter converts Java objects to/from XML — added if JAXB2 is present on the classpath.    MappingJacksonHttpMessageConverter converts to/from JSON — added if Jackson is present on the classpath.    AtomFeedHttpMessageConverter converts Atom feeds — added if Rome is present on the classpath.    RssChannelHttpMessageConverter converts RSS feeds — added if Rome is present on the classpath.  

private Object readWithMessageConverters(MethodParameter methodParam, HttpInputMessage inputMessage, Class paramType)              throws Exception {            MediaType contentType = inputMessage.getHeaders().getContentType();          if (contentType == null) {              StringBuilder builder = new StringBuilder(ClassUtils.getShortName(methodParam.getParameterType()));              String paramName = methodParam.getParameterName();              if (paramName != null) {                  builder.append(‘ ‘);                  builder.append(paramName);              }              throw new HttpMediaTypeNotSupportedException(                      "Cannot extract parameter (" + builder.toString() + "): no Content-Type found");          }            List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>();          if (this.messageConverters != null) {              for (HttpMessageConverter<?> messageConverter : this.messageConverters) {                  allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());                  if (messageConverter.canRead(paramType, contentType)) {                      if (logger.isDebugEnabled()) {                          logger.debug("Reading [" + paramType.getName() + "] as \"" + contentType                                  +"\" using [" + messageConverter + "]");                      }                      return messageConverter.read(paramType, inputMessage);                  }              }          }          throw new HttpMediaTypeNotSupportedException(contentType, allSupportedMediaTypes);      }

private void writeWithMessageConverters(Object returnValue,                  HttpInputMessage inputMessage, HttpOutputMessage outputMessage)                  throws IOException, HttpMediaTypeNotAcceptableException {              List<MediaType> acceptedMediaTypes = inputMessage.getHeaders().getAccept();              if (acceptedMediaTypes.isEmpty()) {                  acceptedMediaTypes = Collections.singletonList(MediaType.ALL);              }              MediaType.sortByQualityValue(acceptedMediaTypes);              Class<?> returnValueType = returnValue.getClass();              List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>();              if (getMessageConverters() != null) {                  for (MediaType acceptedMediaType : acceptedMediaTypes) {                      for (HttpMessageConverter messageConverter : getMessageConverters()) {                          if (messageConverter.canWrite(returnValueType, acceptedMediaType)) {                              messageConverter.write(returnValue, acceptedMediaType, outputMessage);                              if (logger.isDebugEnabled()) {                                  MediaType contentType = outputMessage.getHeaders().getContentType();                                  if (contentType == null) {                                      contentType = acceptedMediaType;                                  }                                  logger.debug("Written [" + returnValue + "] as \"" + contentType +                                          "\" using [" + messageConverter + "]");                              }                              this.responseArgumentUsed = true;                              return;                          }                      }                  }                  for (HttpMessageConverter messageConverter : messageConverters) {                      allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());                  }              }              throw new HttpMediaTypeNotAcceptableException(allSupportedMediaTypes);          }