Hi,
I'm devloping an application that manages files upload and download.
The file itself can be quite large, so is not so usefull laod the file-data everytime in the java object if i have only to know, for exmaple, the filename.

I think something like lazy loading can be really usefull, but for what i've read it's used only with associations and not with internal attributes.

Is there someone that have a good hint??

Such question should go to the regular user forum
Use a blob (lazy as per the spec)
or http://www.hibernate.org/hib_docs/v3/reference/en/html_single/#performance-fetching-lazyproperties

Sorry, i've started thinking about an annotation that could tell hibernate to load the field on-demand. ( like @LazyToOne).
Then i tought to ask something more general cause i've not really get clearly how this annotation works.

I'm already using a java.sql.Blob class for that field. Does hibernate load the field donly when accessed??

I will read the link that you have passed to me.

Thanks

I've used the java.SQL.Blob type, but my test shows that the filed is laoded without using a lazy policy.
Is there an annotation that specify that a field, not an association, as to be loaded only on demand??

Thanks for any reply

P.S.: I explain shortly the test.
I have loaded in the DB a big file ( 148MB ) and when i try to list all the files loaded showing only the filename and the content-type i get this exception:



I think this shows that the field File of the entity is loaded eagerly.

The Blob lazy loading should be done by your driver. So it seems you have a flawed driver.
If you are using MySQl, they don't support lazy blobs

You guessed right... I'm using MySQL.
So the only solution is to have two different entity, one with the Blob field and one without, isn't it?

Maybe i ask in another forum... I'm going OT.

Thanks anyway.

You can use such a pattern
http://www.hibernate.org/41.html

Note if you enhance the class, and use @Lob @Basic(fetch=LAZY) the blob should not be loaded. I'm not 100% sure but I guess so