public DatabaseMapping getMappingFromQueryKey() {
   QueryKey queryKey = getQueryKeyOrNull();
   if ((queryKey == null) || (!(queryKey instanceof DirectQueryKey))) {
     throw QueryException.cannotConformExpression();
   }
   mapping =
       queryKey
           .getDescriptor()
           .getObjectBuilder()
           .getMappingForField(((DirectQueryKey) queryKey).getField());
   if (mapping == null) {
     throw QueryException.cannotConformExpression();
   }
   return mapping;
 }
  /**
   * INTERNAL This method iterates through a collection and gets the values from the objects to
   * conform in an in-memory query. Creation date: (1/19/01 1:18:27 PM)
   */
  public Object valuesFromCollection(
      Object object, AbstractSession session, int valueHolderPolicy, boolean isObjectUnregistered) {
    // in case the mapping is null - this can happen if a query key is being used
    // In this case, check for the query key and find it's mapping.
    boolean readMappingFromQueryKey = false;
    if (getMapping() == null) {
      getMappingFromQueryKey();
      readMappingFromQueryKey = true;
    }

    // For bug 2780817 get the mapping directly from the object.  In EJB 2.0
    // inheritance, each child must override mappings defined in an abstract
    // class with its own.
    DatabaseMapping mapping = this.mapping;
    ClassDescriptor descriptor = mapping.getDescriptor();
    if (descriptor.hasInheritance() && (descriptor.getJavaClass() != object.getClass())) {
      mapping =
          session
              .getDescriptor(object.getClass())
              .getObjectBuilder()
              .getMappingForAttributeName(getName());
      descriptor = mapping.getDescriptor();
    }

    // fetch group support
    if (descriptor.hasFetchGroupManager()) {
      FetchGroupManager fetchGroupManager = descriptor.getFetchGroupManager();
      if (fetchGroupManager.isPartialObject(object)
          && (!fetchGroupManager.isAttributeFetched(object, mapping.getAttributeName()))) {
        // the conforming attribute is not fetched, simply throw exception
        throw QueryException.cannotConformUnfetchedAttribute(mapping.getAttributeName());
      }
    }

    if (mapping.isDirectToFieldMapping()) {
      return ((AbstractDirectMapping) mapping).valueFromObject(object, mapping.getField(), session);
    } else if (mapping.isForeignReferenceMapping()) {
      // CR 3677 integration of a ValueHolderPolicy
      Object valueFromMapping = mapping.getAttributeValueFromObject(object);
      if (!((ForeignReferenceMapping) mapping)
          .getIndirectionPolicy()
          .objectIsInstantiated(valueFromMapping)) {
        if (valueHolderPolicy != InMemoryQueryIndirectionPolicy.SHOULD_TRIGGER_INDIRECTION) {
          // If the client wishes us to trigger the indirection then we should do so,
          // Other wise throw the exception
          throw QueryException
              .mustInstantiateValueholders(); // you should instantiate the valueholder for this to
                                              // work
        }

        // maybe we should throw this exception from the start, to save time
      }
      Object valueToIterate = mapping.getRealAttributeValueFromObject(object, session);
      UnitOfWorkImpl uow = isObjectUnregistered ? (UnitOfWorkImpl) session : null;

      // First check that object in fact is unregistered.
      // toDo: ?? Why is this commented out? Why are we supporting the unregistered thing at all?
      // Does not seem to be any public API for this, nor every used internally?
      // if (isObjectUnregistered) {
      //	isObjectUnregistered = !uow.getCloneMapping().containsKey(object);
      // }
      if (mapping.isCollectionMapping() && (valueToIterate != null)) {
        // For bug 2766379 must use the correct version of vectorFor to
        // unwrap the result same time.
        valueToIterate = mapping.getContainerPolicy().vectorFor(valueToIterate, session);

        // toDo: If the value is empty, need to support correct inner/outer join filtering
        // symantics.
        // For CR 2612601, try to partially replace the result with already
        // registered objects.
        if (isObjectUnregistered && (uow.getCloneMapping().get(object) == null)) {
          Vector objectValues = (Vector) valueToIterate;
          for (int i = 0; i < objectValues.size(); i++) {
            Object original = objectValues.elementAt(i);
            Object clone =
                uow.getIdentityMapAccessorInstance()
                    .getIdentityMapManager()
                    .getFromIdentityMap(original);
            if (clone != null) {
              objectValues.setElementAt(clone, i);
            }
          }
        }

        // For CR 2612601, conforming without registering, a query could be
        // bob.get("address").get("city").equal("Ottawa"); where the address
        // has been registered and modified in the UOW, but bob has not.  Thus
        // even though bob does not point to the modified address now, it will
        // as soon as it is registered, so should point to it here.
      } else if (isObjectUnregistered && (uow.getCloneMapping().get(object) == null)) {
        Object clone =
            uow.getIdentityMapAccessorInstance()
                .getIdentityMapManager()
                .getFromIdentityMap(valueToIterate);
        if (clone != null) {
          valueToIterate = clone;
        }
      }
      return valueToIterate;
    } else if (mapping.isAggregateMapping()) {
      Object aggregateValue = mapping.getAttributeValueFromObject(object);
      // Bug 3995468 - if this query key is to a mapping in an aggregate object, get the object from
      // actual mapping rather than the aggregate mapping
      while (readMappingFromQueryKey
          && mapping.isAggregateObjectMapping()
          && !((AggregateObjectMapping) mapping)
              .getReferenceClass()
              .equals(queryKey.getDescriptor().getJavaClass())) {
        mapping =
            mapping
                .getReferenceDescriptor()
                .getObjectBuilder()
                .getMappingForField(((DirectQueryKey) queryKey).getField());
        aggregateValue = mapping.getRealAttributeValueFromObject(aggregateValue, session);
      }
      return aggregateValue;
    } else {
      throw QueryException.cannotConformExpression();
    }
  }