Java Polymorphism - Selecting correct method based on subtype

Posted by Marty Pitt on Stack Overflow See other posts from Stack Overflow or by Marty Pitt
Published on 2010-05-20T18:00:12Z Indexed on 2010/05/20 18:10 UTC
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Hi

Given the following Class and Service layer signatures:

public class PersonActionRequest {
    PersonVO person
    // ... other fields
}
public class MyServiceLayerClass {

   public void requestAction(PersonActionRequest request)
   {
       PersonVO abstractPerson = request.getPerson();
       // call appropriate executeAction method based on subclass of PersonVO
   }
   private void executeAction(PersonVO person) {}
   private void executeAction(EmployeeVO employee) {}
   private void executeAction(ManagerVO manager) {}
   private void executeAction(UnicornWranglerVO unicornWrangler) {}
}

As discussed here, java will select the best method based on type info at compile time. (Ie., it will always select executeAction(PersonVO person) ).

What's the most appropriate way to select the correct method?

The internet tells me that using instanceof gets me slapped. However, I don't see the appropraite way to select the method without explictly casting abstractPerson to one of the other concrete types.

Thanks

Marty

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