Question

I’d like to be able to call ‘getProgram’ on objects which have that method, without knowing which class they belong to. I know I should use an interface here, but I’m working with someone else’s code and can’t redesign the classes I’m working with. I thought BeanUtils.getProperty might help me, but it seems it only returns strings. Is there something like Beanutils.getProperty that will return a cast-able object? Or another, smarter way to work with two similar classes that don’t share an interface? thanks, -Morgan

Answer 1

Presumably you have a finite number of classes implementing this method, and you can link to them directly. So you don’t need reflection. Reflection is evil.

Say you have a set of classes with the method:

public class LibA { public Program getProgram() { return program; } ... }; public class LibB { public Program getProgram() { return program; } ... }; ... 

Then you just need instanceof/cast pairs. You can put this in a method so that you only need to do it once.

public static Program getProgram(Object obj) {     if        (obj instanceof LibA) {         return              ((LibA)obj).getProgram();     } else if (obj instanceof LibB) {         return              ((LibB)obj).getProgram();     } else {         throw new IllegalArgumentException(obj+' doesn't have a known getProgram');             // Or an appropriate application exception.     } } 

Alternatively you might want to use an adapter:

public interface ProgramContainer {      Program getProgram();     ... }  public class LibAContainer implements ProgramContainer {     private final LibA libA;     public LibAContainer(LibA libA) {         this.libA = libA;     }     public Program getProgram() {         return libA.getProgram();     }     ... }