[Contrib: Evaluation System] Questions about evalsys

[Aaron Zeckoski]

>> 1) I am using XStream to serialize and deserialize EVAL entities for
>> export/import. XStream has a known issue with hibernate's lazy
>> initialization.  Is there a way through the existing EVAL API's to turn off
>> lazy init (i.e. to get a fully initialized object) for entities before they
>> go to XStream?
>
> If there is then I don't know about it. I ended up writing my own
> serializer for EB because I could not make the one for xstream work.
> If you do find a way to make this work then let me know.

I forgot about the reflectutils methods. You could run the objects
through a deepcopy and limit the number of levels. This would make a
copy of the objects which ensures there is no lazy loading left and
limits the amount of data retrieved.

http://reflectutils.googlecode.com/svn/maven/site/apidocs/index.html?org/azeckoski/reflectutils/DeepUtils.html

deepClone is probably what you want.

Hope that helps
-AZ



On Fri, Jan 29, 2010 at 8:41 PM, Aaron Zeckoski <aaronz at vt.edu> wrote:
> On Fri, Jan 29, 2010 at 3:24 PM, Jim Eng <jimeng at umich.edu> wrote:
>> Hi Aaron,
>>
>> I have a few questions I'm hoping you can help me with.
>>
>> 1) I am using XStream to serialize and deserialize EVAL entities for
>> export/import. XStream has a known issue with hibernate's lazy
>> initialization.  Is there a way through the existing EVAL API's to turn off
>> lazy init (i.e. to get a fully initialized object) for entities before they
>> go to XStream?
>
> If there is then I don't know about it. I ended up writing my own
> serializer for EB because I could not make the one for xstream work.
> If you do find a way to make this work then let me know.
>
>> 2) The EvalEmailTemplate class does not have an EID, but we need to import
>> email templates and link from other entities to particular email templates
>> on import. Is it OK to add an EID member to the class and to its hibernate
>> mapping, provided appropriate tests are added?  Is it OK to add a
>> getEmailTemplateByEid(String) method to the Evaluation Service (along with
>> an appropriate test)?
>
> Yeah. Definitely.
>
>
>> 3) There's a problem with trying to update an existing EvalItem.  We
>> discussed this a week or so ago, but I haven't worked it out yet.  When
>> calling EvalAuthoringService.saveItem() and passing in an existing EvalItem
>> to be updated, the saveItem() method retrieves the object again at line 398.
>>  There's a comment there that says you just get back the same object, but
>> that's not my experience.  I get a hibernate exception a few lines later
>> because I'm trying to save a different object than the one that was most
>> recently retrieved from the db. The object is being retrieved at line 398 to
>> check whether it is locked in the db (as opposed to trusting that the object
>> being passed in). Noah mentioned that it might be possible to evict that
>> newly retrieved object from the hibernate session so the other one can be
>> saved.  It occurs to me that maybe this would be better handled by adding a
>> method to check whether an item is locked without actually retrieving it.
>>  There was similar code in save methods for other entity types, but those
>> lines have been commented out, so it looks like the locked property is being
>> checked only when saving items of type EvalItem. (I could mention a few
>> other details, but before I do, I'm wondering if you have a preference about
>> an approach to solving this).
>
> I think we basically stopped using the locks when everyone decided
> they preferred to make duplication rather than reference copied of
> object trees. That got rid of most of the need for the locks.
> That said, I have special methods in the DAO to checks locks which
> might be better to use in this circumstance. On the other hand, it may
> simply be best to remove the lock check entirely since the other ones
> are not really being done anymore.
> I am open to solutions on this and frankly the extra lock check is
> probably overkill. Not trusting the object does mean that a developer
> could change a locked object but I suppose that could happen anyway.
> What do you think of those options? Any of them sound good?
>
> Hope this helps!
> -AZ
>
>
> --
> Aaron Zeckoski (azeckoski (at) vt.edu)
> Senior Research Engineer - CARET - University of Cambridge
> https://twitter.com/azeckoski - http://www.linkedin.com/in/azeckoski
> http://aaronz-sakai.blogspot.com/ - http://tinyurl.com/azprofile
>



-- 
Aaron Zeckoski (azeckoski (at) vt.edu)
Senior Research Engineer - CARET - University of Cambridge
https://twitter.com/azeckoski - http://www.linkedin.com/in/azeckoski
http://aaronz-sakai.blogspot.com/ - http://tinyurl.com/azprofile