Hello,

I am currently working on migration of persistence layer from CMP to BMP using Hibernate as DAO's.

My BMP ejbFindByPrimaryKey method looks like this:

public BeanKey ejbFindByPrimaryKey(BeanKey key) throws FinderException {
try {
BeanDAO dao = (BeanDAO) DAOFactory.getInstance().getDAO(this);
key = dao.findByPrimaryKey(key);
return key;
} catch (ObjectNotFoundDAOException onfde) {
throw new ObjectNotFoundException(onfde.getMessage());
} catch(DAOException ex) {
throw new FinderException(ex.toString());
}
}

while the DAO's findByPrimaryKey method is

public BeanKey findByPrimaryKey(BeanKey pk) throws DAOException {
Session session = null;
try {
session = openSession();
session.load(BeanBean.class, pk.something);
return pk;
} catch (ObjectNotFoundException onfe) {
throw new ObjectNotFoundDAOException("not found");
} catch (HibernateException he) {
throw new DAOException("error");
} finally {
closeSession(session);
}
}

My question is: Is there any other (faster) way of performing the function of findByPrimaryKey in hibernate, that wouldn't try to load the object into memory, instead of it only check whether the object with given id exists?

use session.get() and check for null if you don't want a proxy. How else should it work faster?

Hello,

As I userstand correctly from my experience, Session.get() will load the object if it exists. in this case it will result in loading the object twice:

1. DAO.findByPrimaryKey loads object, returns object primary key, discards the loaded object

2. beans ejbLoad() loads object again

In findByPrimaryKey all I need to know is if the specified object exists and not load them and waste precious time. I thought using JDBC query just to check if the specified id exists would be fastest way for findByPrimaryKey, but perhaps there is a better way to do it in Hibernate? Like lazy loading of objects queried for or something?

how would you just check for existance with JDBC? You can do just the same with HQL like "select a.id from Someclass a where a.id=?" if you mean something like that. I don't actually get what you suggest.

Yes, I meant to select only for id not whole row of data with jdbc. If I do such query with HQL, would the result be loaded into pojo, making all the rest of the fields null except id?

Read the documentation.