Simple use case to show how an InvocationHandler (see https://issues.apache.org/jira/browse/DELTASPIKE-113) would be useful to support mixins for CDI beans.

gistfile1.txt

@InvocationHandlerBinding
public @interface Composed {}

/**
 * MyComponent will be implemented using three mixins
 */
@Composed
public interface MyComponent implements Titled, Comparable2 {}

public interface Titled {
  String getTitle();
}

public interface Comparable2 extends Comparable {
  boolean isLessThan(Comparable object);
  boolean isGreaterThan(Comparable object);
}

@Decorator
public abstract class TitledMixin {
  private String title;

  public String getTitle() {
    return title;
  }
}

@Decorator
public abstract class ComparableMixin implements Comparable2 {
  @Inject @Delegate
  private Comparable comparable;

  public boolean isLessThan(Comparable object) {
    return comparable.compareTo(object) < 0;
  }
  
  public boolean isGreaterThan(Comparable object) {
    return comparable.compareTo(object) > 0;
  }
}

@Decorator
public abstract class TitledComparableMixin implements Titled, Comparable {

  @Inject @Delegate
  private Titled titled;

  public int compareTo(Object object) {
    return titled.getTitle().compareTo(((Titled)object).getTitle());
  }
}

@Composed @InvocationHandler
public ComposedInvocationHandler implements InvocationHandler {
  public Object invoke(Object proxy, Method method, Object[] args) {
    LOG.warn("No mixin found for method " + method);
    return null; //Check, if the return type is a simple type and return the correct default value in that case.
  }
}