Check the existence of the enity

bilyush · **Joined:** Thu Nov 17, 2005 12:59 pm **Posts:** 18

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Hibernate version:3.1.2

I would like to check, if the entity with the given ID exist in the DB. From documentation session.load() should throw an exception and session.get() should return null if there is no the entity with given ID in the DB. Also the doc says, that the session.get() returns:

"If the instance, or a proxy for the instance, is already associated with the session, return that instance or proxy."

A I see from my tests, the session.load() also return the proxy in this case.

I use the SpringDAOSupport, and as I see, spring doesn create the new hibernate session while calling each DAO method. Therefore I see only one solution:
select count(*) from MyObject where myId=id
and check this value.

The my question is: is the another way to check the entity existance?

nathanmoon · **Posted:** Wed Apr 05, 2006 10:51 am

Maybe I'm missing something from your question, but Session.get() will work fine for checking if a record exists in the db. If it returns null, it doesn't exist, if it returns non-null (either an instance or proxy), then the records does exist.

bilyush · **Joined:** Thu Nov 17, 2005 12:59 pm **Posts:** 18

nathanmoon, as I noted above, the Session javadoc says fo the .get() method:
"If the instance, or a proxy for the instance, is already associated with the session, return that instance or proxy."

And as I see from my unit tests, the proxy was created also for the non-existent id. For example, session.get(MyClass, -1) retrive the proxy, with id=-1. My code below:

Code:

    public void updateCatalogInfo(final Catalog catalog)
        throws NoSuchCatalogException, CatalogException {

        final Integer catalogId = catalog.getCatalogId();
        try {

            HibernateTemplate template = getHibernateTemplate();
            Catalog persistantedCatalog
                = (Catalog) template.get(Catalog.class, catalogId);
            if (null == persistantedCatalog) {
                
                //this is unsearchable in the my tests, even for the id=-1
                throw new NoSuchCatalogException("There is no catalog "
                    + "with id = '" + catalogId + "'.");
            }
            template.update(catalog);
        }
        catch (DataAccessException he) {

            logger.error(he);
            throw new CatalogException("Can't update the catalog with id = '"
                + catalogId + "'.", he);
        }
    }