code: public ObjectMetadata getObject(String bucketName, String key, File destinationFile) {
          return this.getObject(new GetObjectRequest(bucketName, key), destinationFile);
      }
docs: Gets the object metadata for the object stored in Bos under the specified bucket and key,
  and saves the object contents to the specified file.
  Returns <code>null</code> if the specified constraints weren't met.
  
  @param bucketName The name of the bucket containing the desired object.
  @param key The key under which the desired object is stored.
  @param destinationFile Indicates the file (which might already exist)
  where to save the object content being downloading from Bos.
  @return All Bos object metadata for the specified object.
  Returns <code>null</code> if constraints were specified but not met.