With the gRPC API for External Tasks we can reuse most of the code base of the Java External Task Client and simply override those classes that take care of the connection between client and server.

In order to make that possible, some minor methods and attributes need to be made accessible in some places.

The gRPC project can serve as a template on how to extend the external task client to use a different protocol. The proposed minor changes could therefore benefit in other future projects as well that try to do a similar thing.