code: public ObjectMetadata getObjectMetadata(GetObjectMetadataRequest request) {
          checkNotNull(request, "request should not be null.");
  
          return this.invokeHttpClient(this.createRequest(request, HttpMethodName.HEAD), GetObjectResponse.class)
                  .getObject().getObjectMetadata();
      }
docs: Gets the metadata for the specified Bos object without actually fetching the object itself.
  This is useful in obtaining only the object metadata, and avoids wasting bandwidth on fetching
  the object data.
  
  <p>
  The object metadata contains information such as content type, content disposition, etc.,
  as well as custom user metadata that can be associated with an object in Bos.
  
  @param request The request object specifying the bucket, key whose metadata is being retrieved.
  @return All Bos object metadata for the specified object.