Return SessionFactory Singleton object for Hibernate 4.3

Question

I am using Hibernate 4.3. I am trying to get the SessionFactory object from a HibernateUtil class. I am trying to get only one SessionFactory object for entire application, i.e. Singleton object for application.

Below is my current code, I want to make it Singleton class.

HibernateUtil.java

public class HibernateUtil {

    private static SessionFactory sessionFactory;
    private static StandardServiceRegistry serviceRegistry; 

    public static SessionFactory getSessionFactory() {
      Configuration configuration = new Configuration();
      configuration.configure();
      serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
      sessionFactory = configuration.buildSessionFactory(serviceRegistry);
      return sessionFactory;
  }

}

Please suggest or provide sample code for this. Thanks.

Answer 1

As suggested I have made the HibernateUtil.java class as Singleton. Find the below code, and please suggest / comment to confirm the correctness of code.

Here is the updated code:

public class HibernateUtil {

private static HibernateUtil instance = null;

   private static SessionFactory sessionFactory;
   private static StandardServiceRegistry serviceRegistry;

   private HibernateUtil(){
        Configuration configuration = new Configuration();
        configuration.configure();
        serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
        sessionFactory = configuration.buildSessionFactory(serviceRegistry);
   }

   public static HibernateUtil getInstance(){
        if(instance == null){
            instance  = new HibernateUtil();
        }
        return instance;
   }

   public synchronized static SessionFactory getSessionFactory() {
        return sessionFactory;
   }

}

Please do correction if the code is not correct, and suggest the correct way.