apollo-core/src/main/java/com/ctrip/framework/foundation/internals/ServiceBootstrap.java/ServiceBootstrap/compare
class ServiceBootstrap:  public static <S extends Ordered> List<S> loadAllOrdered(Class<S> clazz) {
    Iterator<S> iterator = loadAll(clazz);
    List<S> candidates = Lists.newArrayList(iterator);
    Collections.sort(candidates, new Comparator<S>() {
      @Override
      public int compare(S o1, S o2) {
        // the smaller order has higher priority
        return Integer.compare(o1.getOrder(), o2.getOrder());
      }
    });

    return candidates;
  }