The Criteria.uniqueResult()
method make it easier to query a single instance of a persistence object. When no persistence found this method will return a null
value.
package org.kodejava.hibernate;
import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Restrictions;
import org.kodejava.hibernate.model.Genre;
public class UniqueResultExample {
public static Session getSession() throws HibernateException {
String cfg = "hibernate.cfg.xml";
SessionFactory sessionFactory = new Configuration().configure(cfg)
.buildSessionFactory();
return sessionFactory.openSession();
}
public static void main(String[] args) {
try (Session session = getSession()) {
Criteria criteria = session.createCriteria(Genre.class)
.add(Restrictions.eq("id", 1L));
// Convenience method to return a single instance that matches
// the query, or null if the query returns no results.
Object result = criteria.uniqueResult();
if (result != null) {
Genre genre = (Genre) result;
System.out.println("Genre = " + genre.getName());
}
}
}
}
Maven Dependencies
<dependencies>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.6.9.Final</version>
</dependency>
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<version>8.0.33</version>
</dependency>
</dependencies>