Кастомизированные функции движка FEEL

import io.openbpm.bpm.dmn.feel.impl.scala.function.CustomFunction;
import io.openbpm.bpm.dmn.feel.impl.scala.function.FeelCustomFunctionProvider;

import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

public class CustomFunctionProvider implements FeelCustomFunctionProvider {

  protected Map<String, CustomFunction> functions = new HashMap<>();

  public CustomFunctionProvider() {
    CustomFunction function = CustomFunction.create()
        .setParams("x", "y")
        .setFunction(args -> {
          long argX = (long) args.get(0);
          long argY = (long) args.get(1);

          return argX + argY;
        })
        .build();

    functions.put("myFunction", function);
  }

  @Override
  public Optional<CustomFunction> resolveFunction(String functionName) {
    return Optional.ofNullable(functions.get(functionName));
  }

  @Override
  public Collection<String> getFunctionNames() {
    return functions.keySet();
  }

}