public class Test{

    @Id
    private String id;

    @DBRef
    @CascadeSave
    private Contact contact;
}

public class Test{

    @Id
    private String id;

    @DBRef
    @CascadeSave
    private Set<Contact> contacts = new HashSet<>();
}

public class CascadingMongoEventListener extends AbstractMongoEventListener {

private static final Logger logger = LoggerFactory.getLogger(CascadingMongoEventListener.class);

@Autowired
private MongoOperations mongoOperations;

@Override
public void onBeforeConvert(final Object source) {
     ReflectionUtils.doWithFields(source.getClass(), new ReflectionUtils.FieldCallback() {

        public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
            ReflectionUtils.makeAccessible(field);
            try {
                if (field.isAnnotationPresent(DBRef.class) && field.isAnnotationPresent(CascadeSave.class)) {
                    final Object fieldValue = field.get(source);
                    if (fieldValue != null) {

                        if (Collection.class.isAssignableFrom(field.getType())) {
                            @SuppressWarnings("unchecked")
                            Collection models = (Collection) fieldValue;
                            for (Object model : models) {
                               mongoOperations.save(model);
                            }
                        } else {
                            mongoOperations.save(fieldValue);
                        }
                    }
                }
            } catch (Exception e) {
                logger.error(e.getMessage());
                e.printStackTrace();
            }
        }
    });
}

private static class DbRefFieldCallback implements ReflectionUtils.FieldCallback {
    private boolean idFound;

    public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
        ReflectionUtils.makeAccessible(field);
        if (field.isAnnotationPresent(Id.class)) {
            idFound = true;
        }
    }

    public boolean isIdFound() {
        return idFound;
    }
}
}