Hi,

I'm facing the problem of having some non persistent attributes which are caculated at runtime. These attributes obviously do not get cached in second level cache (which is essentially just the JDBC data).

This behaviour forces me to recalculate the values over and over again, which is everything but satisfying (especially since some of the calculations are REALLY expensive).

I also tried a little workaround using a custom UserType. Although I ended up with my attribute being cached there is some SERIOUS problem I'm having with this approach:

1. I really don't think that any of my non persistent attributes should be specified in the mapping file!

2. Beeing an attribute of the mapping file it needs to be mappend to a column . Also you could use any column in insert=false, update=false mode or formula this is more than a 'little hack' to me... it's just dirty style!

3. The idea of having a seperate class / user type for every transient attribute just to be able to cache... I don't think I have to say anything more on this. Also all these methods like nullSafeGet(..), sqlTypes(), ... stuff I just don't need here

As far as I know HbmBinder is used to parse the mapping file and analyize which attributes are beeing cached, what is the pk and so on. Is there any way to enhance this (or any other) class to also consider the transient properties of my domain objects (or cache the whole object like TopLink does)?

This problem seems to be sooo straight forward to me that I'm almost sure that I'm missing something here. It can't be that tricky, can it?! #
And if there is really no other way I'm sure some of you guys (if not all) are in the same situation of not wanting to throw away already initialized data...PLEASE letme know what the heck you are doing to get around this issue in a nice and clean way.

This has really been giving me the biggest headaches for the last weeks!

Looking forward to your answers... :-)

Why on earth not? The mapping file is for mapping to the cache, as well as to the database.




This is not true. Hibernate properties do not need to be mapped to a column.




I don't see a priori why you would need more than one UserType to handle all cached attributes. At least all immutable attributes can be handled by one type i guess.




Ok, thats just silly.


Hibernate will never implement a shared object cache.

That's what I call a quick answer :-) ...


Not true? When I tried without a column name hibernate tried looking up a database column with the same name as the property which of course resulted in an exception. What am I missing here?

Assuming the above metioned works...this would lead to all my transient properties being initalized when the object is loaded, wouldn't it? (Unless I don't wan't to configure lazy property fetching for these attributes)

Can I modify the attributes from everywhere in my code at any time, even if the jdbc part is immutable, or does the initalization has to happen in the UserType and cannot be touched later on?

Thanks a lot!

ok... been trying to figure out how I can map property without specifying a column for the whole night.

What I'm ending up with is always the same exception:



'test' is obviously the name of my transient attribute which is also used as column name by default.

The exception makes sence to me, considering the following statement from the hibernate documentaion in section 6.1.9. :


and also


So how can I specify properties not related to any columns then? How would the entry in the mapping file look like???
Please help... :-(

It must be better to calcultate stuff using queries, move calculations from entity to some "business method" or DAO (entity can go as parameter) and use query cache. I think it is a good way, it can help to avoid dependencies on infrastructure to reuse domain data structures (entities) or to decorate calculations. I always use course grained model myself for many reasons.

Guys... you are fully confusing me....


Could you please explain this? I'm really interested in what Gavin mentioned: using the mapping file as mapping to the cache using only a single UserType for all transient properties.

If possible I do not want to map all my non persistent properties like this:


Well...in the end this does what I wanted -> cache the transient attribute 'salesData'. But this is really everything but elegant and can't be the recommended way on doing it, don't you think?

Things I don't like here (besides the fact that I have to specify ALL attributes in the mapping file again) that I have to specify a column (in this case I used an already existing one and mapped in read-only)

Also I want to be able to modify the value at any time I wish (so not read only) and update the second level cache with the new values. I don't know whether this is possible with these settings...

If you could please clarify (preferably with a short code snippet) I would be really grateful.

Thanks a lot!

hey... it's been a while now and I solved this problem by 'refactoring' my object model and take care of the caching for transient objects myself..

Anyway... I'm still REALLY curious what gavin was talking about in his answer quoted above. How could I map a property without mapping to a column?

If sombody could please clarify this... a simple 'No.. not possible' would be enough. If it is possible, however, please point me to a resource where I can find some more information on that.

Thanks a lot!
TJ

Hello tylor,

I am interested in the same.
Can you explain how you have resolved the issue?
Can put examples please?

Thank you very much,

what a crazy feature you are talking about!!

why should hibernate have such a feature! is it realted to ORM!?! of course not!

why don't you cache your calculation data yourself?! there are plenty of cache products, so just use them and refactor your DAOs to cache calculated data.

hibernate handles this just fine.

it's called UserType and/or formula.