Question

For a better understanding of my question, see the following classes:

public interface Invoker<R> {
  public String getName();
  public R getResult();
}

Implementation:

public class RepairFetcher implements Invoker<List<String>> {

  @Override
  public String getName() {
    return this.getClass().getSimpleName();
  }

  @Override
  public List<String> getResult() {
    return new ArrayList<String>();
  }

}

The class where it goes wrong:

public class OperationService {

   public <R> R invoke(Class<R> invoker, Object... parameters) {
     WebserviceOperation<R> operation = new WebserviceOperation<R>(invoker);
     Invoker<R> instance = operation.getInstance();

     return instance.getResult();
   }

}

The main class:

public class Main {

  public static void main(String[] args) {

    OperationService operationService = new OperationService();
    operationService.invoke(RepairFetcher.class, new Object[] {});

  }

}

The problem:
At this moment the method

operationService.invoke(RepairFetcher.class, new Object[] {});

returns an RepairFetcher, which is not so weird because of the argument in the invoke method:

Class invoker

Which returns R, which is a RepairFetcher.class.

What I want
I don’t want the invoke method to return the RepairFetcher class, but I want it to return the declared Type, which is List< String>.

Is this possible, and if so, how to implement this?

Thanks in advance!

Answer 1

Not sure, but try:

public <T, R extends Invoker<T>> T invoke(Class<R> invoker, Object... parameters) {