Creating a single SessionFactory per application, without using static methods - spring

Question

I have a helper class called HibernateUtil, which creates a SessionFactory and returns a session. The class works fine, except it creates problems with mocking because Mockito can't use static methods.
The simple solution would seem to create an instance of the class, except I need to make sure there is only one SessionFactory in the application. How do I do that without using static methods?
public class HibernateUtil {
private static final Log logger = LogFactory.getLog(SessionFactory.class);
private static final SessionFactory sessionFactory = createSessionFactory();
private static SessionFactory createSessionFactory() {
logger.info("createSessionFactory called");
Configuration configuration = new Configuration().configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());
return configuration.buildSessionFactory(builder.build());
}
private static SessionFactory getSessionFactory() {
return sessionFactory;
}
public static Session getSession() {
Session session = null;
try {
session = HibernateUtil.getSessionFactory().getCurrentSession();
if (!session.isOpen()) {
session = HibernateUtil.getSessionFactory().openSession();
}
} catch (Exception e) {
e.printStackTrace();
}
return session;
}
}
Edit: Thanks for the replies! I think I'll call it a night and tackle this again tomorrow morning.

Answer 1

The alternative is to use dependency injection, but by the looks of your code you're not doing that.
You could use Spring or another IoC container to do the IoC... or diy-di
Another alternative (although a bit hacky) is to have the same "static" interface, but delegate to another object which can be replaced in the tests. By default the backing implementation uses Hibernate and in your tests you can replace that implementation with a mocked instance.

Answer 2

If you don't want to use the spring hibernate support, you can change your class to:
package com.captain.oh.captain
#Component // singletonbean
public class HibernateUtil {
private static final Log logger = LogFactory.getLog(SessionFactory.class);
private SessionFactory sessionFactory;
#PostConstruct
private void createSessionFactory() {
logger.info("createSessionFactory called");
Configuration configuration = new Configuration().configure();
StandardServiceRegistryBuilder builder = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties());
sessionFactory = configuration.buildSessionFactory(builder.build());
}
private SessionFactory getSessionFactory() {
return sessionFactory;
}
public Session getSession() {
Session session = null;
try {
session = HibernateUtil.getSessionFactory().getCurrentSession();
if (!session.isOpen()) {
session = HibernateUtil.getSessionFactory().openSession();
}
} catch (Exception e) {
e.printStackTrace();
}
return session;
}
}
And autowire it in another components (#Autowired HibernateUtil). Don't forget to add the package (com.captain.oh.captain) to your scan packages (in application-context.xml or in your #Configuration class)
Also note that your getSession method is not Thread-safe

Answer 3

Instead of using the HibernateUtil directly in your code, you can hide it behind an interface:
public interface HibernateSessionProvider() {
Session getSession();
}
with a default implementation:
public class DefaultHibernateSessionProvider() implements HibernateSessionProvider {
#Override
public Session getSession() {
return HibernateUtil.getSession();
}
}
Then you can mock the HibernateSessionProvider during testing. This approach works with or without Sprting's dependency injection.