Package jakarta.ws.rs.ext

Interface MessageBodyWriter<T>

  • Type Parameters:
    T - the type that can be written.
    public interface MessageBodyWriter<T>
    Contract for a provider that supports the conversion of a Java type to a stream. A MessageBodyWriter implementation may be annotated with Produces to restrict the media types for which it will be considered suitable. The MessageBodyWriter pipeline is only invoked if there is a non-null response entity.

    Providers implementing MessageBodyWriter contract must be either programmatically registered in a JAX-RS runtime or must be annotated with @Provider annotation to be automatically discovered by the JAX-RS runtime during a provider scanning phase.

    Since:
    1.0
    Author:
    Paul Sandoz, Marc Hadley
    See Also:
    Provider, Produces

    • Method Detail

      • isWriteable

        boolean isWriteable​(Class<?> type,
                    Type genericType,
                    Annotation[] annotations,
                    MediaType mediaType)
        Ascertain if the MessageBodyWriter supports a particular type.
        Parameters:
        type - the class of instance that is to be written.
        genericType - the type of instance to be written, obtained either by reflection of a resource method return type or via inspection of the returned instance. GenericEntity provides a way to specify this information at runtime.
        annotations - an array of the annotations attached to the message entity instance.
        mediaType - the media type of the HTTP entity.
        Returns:
        true if the type is supported, otherwise false.

      • getSize

        default long getSize​(T t,
                     Class<?> type,
                     Type genericType,
                     Annotation[] annotations,
                     MediaType mediaType)
        Originally, the method has been called before writeTo to ascertain the length in bytes of the serialized form of t. A non-negative return value has been used in a HTTP Content-Length header.

        As of JAX-RS 2.0, the method has been deprecated and the value returned by the method is ignored by a JAX-RS runtime. All MessageBodyWriter implementations are advised to return -1 from the method. Responsibility to compute the actual Content-Length header value has been delegated to JAX-RS runtime.

        Parameters:
        t - the instance to write
        type - the class of instance that is to be written.
        genericType - the type of instance to be written. GenericEntity provides a way to specify this information at runtime.
        annotations - an array of the annotations attached to the message entity instance.
        mediaType - the media type of the HTTP entity.
        Returns:
        length in bytes or -1 if the length cannot be determined in advance.

      • writeTo

        void writeTo​(T t,
             Class<?> type,
             Type genericType,
             Annotation[] annotations,
             MediaType mediaType,
             MultivaluedMap<String,​Object> httpHeaders,
             OutputStream entityStream)
      throws IOException,
             WebApplicationException
        Write a type to an HTTP message. The message header map is mutable but any changes must be made before writing to the output stream since the headers will be flushed prior to writing the message body.
        Parameters:
        t - the instance to write.
        type - the class of instance that is to be written.
        genericType - the type of instance to be written. GenericEntity provides a way to specify this information at runtime.
        annotations - an array of the annotations attached to the message entity instance.
        mediaType - the media type of the HTTP entity.
        httpHeaders - a mutable map of the HTTP message headers.
        entityStream - the OutputStream for the HTTP entity. The implementation must not close the output stream.
        Throws:
        IOException - if an IO error arises.
        WebApplicationException - if a specific HTTP error response needs to be produced. Only effective if thrown prior to the message being committed.