add support for class extension and interface in Java generator

hi i would like to have the generated java class to extend or implement an interface. the generated class should look something like

package com.acme.ml;
public class MyClassifier implements com.acme.domain.MyInterface {
   public double[] getScore(double[] input) {
   }
}

notice the need to remove the static modifier from the method getScore

the need is to have multiple models running via calling the interface.

[izeigerman]

Hey @yarix thank you so much for reporting this as well as for you PR!

Perhaps I’m missing the point but it seems like this functionality is somewhat redundant in m2cgen and goes beyond what this library is suppose to do.

I’d argue that the manual modification of the generated code is not required either. In OOP world the problem of adapting one interface to another has been long solved by the Adapter (aka Wrapper) design patter.

For example in the application code it’s fairly easy to do the following:

class MyClassifierAdapter implements com.acme.domain.MyInterface {
   public double[] getScore(double[] input) {
      return MyClassifier.score(input);
   }
}

This entity has to be created once and can never be revisited even if the model changes.

Alternatively this can be solved in an even more straightforward way if the MyInterface is a SAM (Single Abstract Method) interface and you’re using Java >=8:

MyInterface classifier1 = (input) -> MyClassifier1.score(input);
MyInterface classifier2 = (input) -> MyClassifier2.score(input);

This is even less verbose.

Given the last example, I don’t see much value in bringing interface support to m2cgen.

Please let us know what you think!

[StrikerRUS]

I’m going to close this issue according to the following statements:

m2cgen tries to generate as minimal as possible working code that can be run from outer piece of code.

Given the last example, I don’t see much value in bringing interface support to m2cgen.

Thanks a lot for using m2cgen and for bringing this discussion up!