Spring Consider adding "ObjectProvider#getIfNotUnique" and its variants

I write a library on spring-boot and it is used by multiple apps. Since it is a library, I do not know what beans are defined up front; thus I use ObjectProvider often.

Currently, to check whether the beans are not unique(with semantics of @Primary is the unique), we need to use List or iterate and check the size.

To streamline the API, it is nice to have getIfNotUnique and its variant methods available in ObjectProvider.

Something like: - List<T> getIfNotUnique() - List<T> getIfNotUnique(Supplier<List<T>> defaultSupplier) - void ifNotUnique(Consumer<List<T>> consumer)

If ordering is the matter, may need to separate APIs for ordered and not ordered.

Comment From: sdeleuze

Aren't stream() and orderedStream() (potentially used in combination with collect(Collectors.toList())) good enough for this kind of use cases?

Comment From: ttddyy

Yes, it is possible to achieve with existing APIs, but I feel it is nice if ObjectProvider provides more enrich APIs. For this case, analogous to ifAvailable or ifUnique and their variants; so that, the programming style can be unified.

Similar to https://github.com/spring-projects/spring-framework/issues/23774, the more I use ObjectProvider, the better if it had more APIs covering usage patterns.

Comment From: ttddyy

For implementation side, if it only scratch API surface with default method, it would be something like:

default void ifNotUnique(Consumer<List<T>> consumer) {
  List<T> list = stream().collect(Collectors.toList());
  if (list.size() > 1) {
    consumer.accept(list);
  }
}

If it goes to bean factory reusing existing impl:

@Nullable
private Stream<T> notUniqueStream() {
  String[] beanNames = getBeanNamesForTypedStream(requiredType);
  Set<T> matchingBeans = new HashSet<>(beanNames.length);
  for (String beanName : beanNames) {
    Object beanInstance = getBean(beanName);
    if (!(beanInstance instanceof NullBean)) {
      matchingBeans.add((T) beanInstance);
    }
  }

  if (matchingBeans.size() < 2) {
    return null;
  }

  return matchingBeans.stream();
}

Or, if supporting from bottom implementation, DefaultListableBeanFactory#resolveNamedBean may need to allow returning list of beans...

Comment From: snicoll

Thanks for the suggestion but I don't think adding ifNotUnique variant is warranted for such API, especially when you can achieve the same goal using the existing method.