Getting a unique result

[Tama-Chan]

Hi everybody,

This is an improvement proposition. On several occasions I needed to get a unique result out of a query; that is I expected to get only one result, and getting more than one would be considered an error that I would have to deal with.

The Hibernate API offers different ways to implement this, the easiest one probably being to use a Query object and use the query.uniqueResult() method. Other ways involve the Criteria API.

I haven't found any easy way to do so through the HibernateTemplate however. Did I miss it?
Otherwise, I propose to add the following method to the HibernateTemplate class :

public Object uniqueResult(final String queryString, final Object[] values) throws DataAccessException {
	try {
		return (List) execute(new HibernateCallback() {
			public Object doInHibernate(Session session) throws HibernateException {
				Query queryObject = session.createQuery(queryString);
				prepareQuery(queryObject);
				if (values != null) {
					for (int i = 0; i < values.length; i++) {
						queryObject.setParameter(i, values[i]);
					}
				}
				return queryObject.uniqueResult();
			}
		}, true);
	} catch (NonUniqueResultException e) {
		throw new IncorrectResultSizeDataAccessException(e.getMessage(), 1);
	}
}

or:

public Object uniqueResult(final String queryString, final Object[] values) throws DataAccessException {
	List results = find(queryString, values);
	if (results.size() > 1)
		throw new IncorrectResultSizeDataAccessException(1);
	
	return results.get(0);
}

[Andrei Stefan]

Why don't you try this:

import org.springframework.dao.support.DataAccessUtils;
...
Object someObject = DataAccessUtils.uniqueResult(getHibernateTemplate().find("your_query"));

[karldmoore]

I think you are right. You'd have to call uniqueResult on the query to do this for you. There are a few things like this where you have to use the HibernateCallback. If you do want the change, JIRA would be your best bet.