Class AbstractHttpMessageConverter<T>

java.lang.Object
org.springframework.http.converter.AbstractHttpMessageConverter<T>
Type Parameters:
T - the converted object type
All Implemented Interfaces:
HttpMessageConverter<T>
Direct Known Subclasses:
AbstractGenericHttpMessageConverter, AbstractSmartHttpMessageConverter, AbstractWireFeedHttpMessageConverter, AbstractXmlHttpMessageConverter, ByteArrayHttpMessageConverter, ObjectToStringHttpMessageConverter, ProtobufHttpMessageConverter, ResourceHttpMessageConverter, SourceHttpMessageConverter, StringHttpMessageConverter
public abstract class AbstractHttpMessageConverter<T> extends Object implements HttpMessageConverter<T>
Abstract base class for most HttpMessageConverter implementations.

This base class adds support for setting supported MediaTypes, through the supportedMediaTypes bean property. It also adds support for Content-Type and Content-Length when writing to output messages.

Since:
3.0
Author:
Arjen Poutsma, Juergen Hoeller, Sebastien Deleuze

  • Field Details

    • logger

      protected final org.apache.commons.logging.Log logger
      Logger available to subclasses.

  • Constructor Details

    • AbstractHttpMessageConverter

      protected AbstractHttpMessageConverter()
      Construct an AbstractHttpMessageConverter with no supported media types.
      See Also:

    • AbstractHttpMessageConverter

      protected AbstractHttpMessageConverter(MediaType supportedMediaType)
      Construct an AbstractHttpMessageConverter with one supported media type.
      Parameters:
      supportedMediaType - the supported media type

    • AbstractHttpMessageConverter

      protected AbstractHttpMessageConverter(MediaType... supportedMediaTypes)
      Construct an AbstractHttpMessageConverter with multiple supported media types.
      Parameters:
      supportedMediaTypes - the supported media types

    • AbstractHttpMessageConverter

      protected AbstractHttpMessageConverter(Charset defaultCharset, MediaType... supportedMediaTypes)
      Construct an AbstractHttpMessageConverter with a default charset and multiple supported media types.
      Parameters:
      defaultCharset - the default character set
      supportedMediaTypes - the supported media types
      Since:
      4.3

  • Method Details

    • setSupportedMediaTypes

      public void setSupportedMediaTypes(List<MediaType> supportedMediaTypes)
      Set the list of MediaType objects supported by this converter.

    • getSupportedMediaTypes

      public List<MediaType> getSupportedMediaTypes()
      Description copied from interface: HttpMessageConverter
      Return the list of media types supported by this converter. The list may not apply to every possible target element type and calls to this method should typically be guarded via canWrite(clazz, null. The list may also exclude MIME types supported only for a specific class. Alternatively, use HttpMessageConverter.getSupportedMediaTypes(Class) for a more precise list.
      Specified by:
      getSupportedMediaTypes in interface HttpMessageConverter<T>
      Returns:
      the list of supported media types

    • setDefaultCharset

      public void setDefaultCharset(@Nullable Charset defaultCharset)
      Set the default character set, if any.
      Since:
      4.3

    • getDefaultCharset

      public @Nullable Charset getDefaultCharset()
      Return the default character set, if any.
      Since:
      4.3

    • canRead

      public boolean canRead(Class<?> clazz, @Nullable MediaType mediaType)
      This implementation checks if the given class is supported, and if the supported media types include the given media type.
      Specified by:
      canRead in interface HttpMessageConverter<T>
      Parameters:
      clazz - the class to test for readability
      mediaType - the media type to read (can be null if not specified); typically the value of a Content-Type header.
      Returns:
      true if readable; false otherwise

    • canRead

      protected boolean canRead(@Nullable MediaType mediaType)
      Returns true if any of the supported media types include the given media type.
      Parameters:
      mediaType - the media type to read, can be null if not specified. Typically the value of a Content-Type header.
      Returns:
      true if the supported media types include the media type, or if the media type is null

    • canWrite

      public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType)
      This implementation checks if the given class is supported, and if the supported media types include the given media type.
      Specified by:
      canWrite in interface HttpMessageConverter<T>
      Parameters:
      clazz - the class to test for writability
      mediaType - the media type to write (can be null if not specified); typically the value of an Accept header.
      Returns:
      true if writable; false otherwise

    • canWrite

      protected boolean canWrite(@Nullable MediaType mediaType)
      Returns true if the given media type includes any of the supported media types.
      Parameters:
      mediaType - the media type to write, can be null if not specified. Typically the value of an Accept header.
      Returns:
      true if the supported media types are compatible with the media type, or if the media type is null

    • read

      public final T read(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException
      This implementation simple delegates to readInternal(Class, HttpInputMessage). Future implementations might add some default behavior, however.
      Specified by:
      read in interface HttpMessageConverter<T>
      Parameters:
      clazz - the type of object to return. This type must have previously been passed to the canRead method of this interface, which must have returned true.
      inputMessage - the HTTP input message to read from
      Returns:
      the converted object
      Throws:
      IOException - in case of I/O errors
      HttpMessageNotReadableException - in case of conversion errors

    • write

      public final void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException
      This implementation sets the default headers by calling addDefaultHeaders(HttpHeaders, T, MediaType), and then calls writeInternal(T, HttpOutputMessage).
      Specified by:
      write in interface HttpMessageConverter<T>
      Parameters:
      t - the object to write to the output message. The type of this object must have previously been passed to the canWrite method of this interface, which must have returned true.
      contentType - the content type to use when writing. May be null to indicate that the default content type of the converter must be used. If not null, this media type must have previously been passed to the canWrite method of this interface, which must have returned true.
      outputMessage - the message to write to
      Throws:
      IOException - in case of I/O errors
      HttpMessageNotWritableException - in case of conversion errors

    • addDefaultHeaders

      protected void addDefaultHeaders(HttpHeaders headers, T t, @Nullable MediaType contentType) throws IOException
      Add default headers to the output message.

      This implementation delegates to getDefaultContentType(Object) if a content type was not provided, set if necessary the default character set, calls getContentLength(T, MediaType), and sets the corresponding headers.

      Throws:
      IOException
      Since:
      4.2

    • getDefaultContentType

      protected @Nullable MediaType getDefaultContentType(T t) throws IOException
      Returns the default content type for the given type. Called when write(T, MediaType, HttpOutputMessage) is invoked without a specified content type parameter.

      By default, this returns the first element of the supportedMediaTypes property, if any. Can be overridden in subclasses.

      Parameters:
      t - the type to return the content type for
      Returns:
      the content type, or null if not known
      Throws:
      IOException

    • getContentLength

      protected @Nullable Long getContentLength(T t, @Nullable MediaType contentType) throws IOException
      Returns the content length for the given type.

      By default, this returns null, meaning that the content length is unknown. Can be overridden in subclasses.

      Parameters:
      t - the type to return the content length for
      Returns:
      the content length, or null if not known
      Throws:
      IOException

    • supportsRepeatableWrites

      protected boolean supportsRepeatableWrites(T t)
      Indicates whether this message converter can write the given object multiple times.

      The default implementation returns false.

      Parameters:
      t - the object t
      Returns:
      true if t can be written repeatedly; false otherwise
      Since:
      6.1

    • supports

      protected abstract boolean supports(Class<?> clazz)
      Indicates whether the given class is supported by this converter.
      Parameters:
      clazz - the class to test for support
      Returns:
      true if supported; false otherwise

    • readInternal

      protected abstract T readInternal(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException
      Abstract template method that reads the actual object. Invoked from read(Class, HttpInputMessage).
      Parameters:
      clazz - the type of object to return
      inputMessage - the HTTP input message to read from
      Returns:
      the converted object
      Throws:
      IOException - in case of I/O errors
      HttpMessageNotReadableException - in case of conversion errors

    • writeInternal

      protected abstract void writeInternal(T t, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException
      Abstract template method that writes the actual body. Invoked from write(T, MediaType, HttpOutputMessage).
      Parameters:
      t - the object to write to the output message
      outputMessage - the HTTP output message to write to
      Throws:
      IOException - in case of I/O errors
      HttpMessageNotWritableException - in case of conversion errors