Hi,

I have an entity Country, which is used in many places in my application (Person, Address, ...). As I know there is only a small number of countries (less than 250), I want to have all Country instances in the second level cache.

Now, if I query a Person instance, I want Hibernate to not query the database for the country property, but take it from the cache.

I can achieve this by defining the country property as lazily loaded, then access the property, and it will be read from the cache.

But I want to eagerly load the country property. This always creates SQL containing a "left outer join". Is there a way to instruct Hibernate to use the 2nd level cache in this case? Something like: "For this property, I know that the instance should be in the 2nd level cache, so do not read it in the SQL query, only read the primary key and fetch the instance from the cache. Do a second select in case the cache is not yet fully populated".

Hibernate version: 3.3.0SP1

Thanks,

Christoph

As far as I remember, you should mark the Country class as "lazy" in the class mapping. Something like:



This will tell Hibernate to create a proxy for it when referenced from another entity (though a many-to-one relationship). Note: "true" might already by the default, but certainly don't set it to false...

You can (or should - don't remember), also mark the many-to-one relationship as lazy as well (it might be false per default) - provided it is not nullable (see Hibernate doc on the subject).


With all this set, loading an Employee won't hit the Country table. Instead, the firstime the getCountry() method is invoked, Hibernate will attempt to load the Country by ID - which will be retrieved from the second level cache (provided you have a cache it).

Hope it helps..

Hi,

Just wondering...wouldn't it be enough to simply enable second-level caching for the Country entity (ie add <cache usage="read-write" /> to the hibernate mapping for Country)?

You did mention that a SELECT query is allowed if the cache is not fully populated (ie if the country record is not found in the cache). Doing the above will ensure that the Country entity will remain in and always be loaded from the 2nd-level cache after the first SELECT for each record.