@Override
  public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations,
    MediaType mediaType) {
    return mediaType == null || MediaType.APPLICATION_JSON_TYPE.isCompatible(mediaType);
  }
Implements JSON serialization via {@link Gson} for JAX-RS.
hbase-http/src/main/java/org/apache/hadoop/hbase/http/gson/GsonMessageBodyWriter.java