尽管 @transactional，但未能懒惰地初始化角色集合

Question

在以下控制器内部，

   @Transactional
   @PostMapping(PATH_VARIABLE)
   public void assignStuff(
         @PathVariable final long someNo,
         @PathVariable final long someId)
         throws AccessDeniedException, ValidationException, ResourceNotFoundException
   {
      final Set<SomeEntity> createdEntities = someService.assignSomething(
            resolveData(someNo, someId)
      );

      if (CollectionUtils.isNotEmpty(createdEntties))
      {
         anotherService.publishPackageDataChangeEvent(someNo);
      }
   }

以下例外是

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: someEntity, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:582)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:201)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:561)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:132)
    at org.hibernate.collection.internal.PersistentSet.iterator(PersistentSet.java:163)
    at java.util.Spliterators$IteratorSpliterator.estimateSize(Spliterators.java:1821)
    at java.util.Spliterator.getExactSizeIfKnown(Spliterator.java:408)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    at aThirdService.thingsChanged(SomeCalculator.java:61)

从其他” @transactional，对吗？那为什么还会发生呢？