ComponentValidator.java

public class ComponentValidator {

    private static final ComponentValidator _instance;

    static {
        _instance = new ComponentValidator();
    }

    private ComponentValidator() {
    }

    public static ComponentValidator getInstance() {
        return _instance;
    }

    public Response validate(Object instance) {
        List<AutoValidatedUserInputComponent> components = new ArrayList<>();
        for (Field field : instance.getClass().getDeclaredFields()) {
            if (!field.isAnnotationPresent(ValidComponent.class)) {
                continue;
            }

            Object possibleComponent = getPossibleComponent(instance, field);
            if (possibleComponent == null) {
                continue;
            }

            if (possibleComponent instanceof AutoValidatedUserInputComponent) {
                AutoValidatedUserInputComponent component = (AutoValidatedUserInputComponent) possibleComponent;
                if (component.hasValidInput()) {
                    continue;
                }
                    components.add(component);
            }
        }
        return new Response(components);
    }

    private Object getPossibleComponent(Object instance, Field field) {
        Object possibleComponent = null;
        try {
            possibleComponent = field.get(instance);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        }
        return possibleComponent;
    }

    public class Response{
        List<AutoValidatedUserInputComponent> components;
        public Response(List<AutoValidatedUserInputComponent> components) {
            this.components = components;
        }

        public boolean isValid() {
            return components != null && components.isEmpty();
        }

        public List<AutoValidatedUserInputComponent> getComponents() {
            return components;
        }
    }
}