Question

I am trying to use Java protobuf stubs inside Matlab. I generated the Java stub and corresponding jar file in Eclipse. I then take the jar file and add it to the Matlab path. In Matlab I do the following:

import raven.aos.*; 
import raven.aos.Messages.*;
image = Image.newBuilder();

At this point I get an error message that says:

??? Undefined variable "Image" or class "Image.newBuilder".
Error in ==> pub>pub.pub at 16
image = Image.newBuilder();

I have successfully been able to use the Java jar in a Java project using the exact same syntax. So this validates that my stub is correct. I have also successfully imported and used a different Java library, zmq.jar, in my Matlab project, so to a certain extent this verifies that I know how to import jar files properly into Matlab.

I’ve refrained from attaching the generated Java stub file since it is very long. I hope that someone can point out what I’m doing wrong with just the code that I’ve provided. If required, I will add the stub source.

Thanks in advance!

Answer 1

Because generated protocol buffer message classes are inner classes, you need to use Matlab’s javaMethod command to get to the static methods. Import statement will not work. Using your example:

image = javaMethod('newBuilder','raven.aos.Messages$Image');

http://www.mathworks.com/help/techdoc/ref/javamethod.html