How to use the Query.uniqueResult () method in Hibernate
This article will explain in detail how to use the Query.uniqueResult () method in Hibernate. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.
Reread the hibernate reference manual and find that the query interface provides a better way to get instances when it is clear that there is only one instance or it is null. PublicObjectuniqueResult () throwsHibernateException returns: a single instance or null throws: when the returned instance is larger than one, the corresponding usage of throwing NonUniqueResultException is as follows:
Query.uniqueResult () in Hibernate
If multiple values are thrown incorrectly
If there is only one value, an object is returned
If there is no value, return null
PublicObjectuniqueResult () throwsHibernateException returns: single instance or null throw: throw NonUniqueResultException when the returned instance is greater than one
When it is determined that there is only one instance returned or is null, then uniqueResult () is the best choice, using the following methods:
PublicUserget (Stringid) {
Sessionsession=HibernateUtil.getSessionFactory () .openSession ()
Stringhql= "fromUseruwhereu.id=?"
Return (User) session.createQuery (hql) .setString (0memid) .uniqueResult ()
}
Use of the HibernateuniqueResult method
In the past, when writing code, it was inevitable to write the login part. When getting user, it is possible to return only one user instance, or null. It was previously implemented using the following methods.
PublicUserget (Stringid) {
Sessionsession=HibernateUtil.getSessionFactory () .openSession ()
Stringhql= "fromUseruwhereu.id=?"
Listlist=session.createQuery (hql) .setString (0recom id) .list ()
If (list.size ()) = = 1) {
Return (User) list.get (0)
} else {
Returnnull
}
}
[java]
PublicUserget (Stringid) {
Sessionsession=HibernateUtil.getSessionFactory () .openSession ()
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