jpa-second-level-cache-test.java

// Testing the jpa (hibernate) second level cache by running different way of findById method

    public UserSession findById(String id) {
        System.out.println("Running UserSession.findById");
        Session session = getEntityManager().unwrap(Session.class);
        SessionFactory sessionFactory = session.getSessionFactory();
        String rName = "test.ear/model.jar#model.com.test.app.authentication.model.UserSession";
        long oldMissCount = sessionFactory.getStatistics().getSecondLevelCacheStatistics(rName).getMissCount();
        long oldHitCount = sessionFactory.getStatistics().getSecondLevelCacheStatistics(rName).getHitCount();

//        the following line doesn't fetch from second level cache
//        TypedQuery<UserSession> query = getEntityManager().createNamedQuery(UserSession.BY_ID, UserSession.class);
//        query.setParameter("id", id);
//        UserSession userSession = query.getSingleResult();

//      this will fetch from second level cache
        UserSession userSession = getEntityManager().find(id);

        long newMissCount = sessionFactory.getStatistics().getSecondLevelCacheStatistics(rName).getMissCount();
        long newHitCount = sessionFactory.getStatistics().getSecondLevelCacheStatistics(rName).getHitCount();

        System.out.println("old hit count : " + oldHitCount + ", old miss count : " + oldMissCount);
        System.out.println("new hit count : " + newHitCount + ", new miss count : " + newMissCount);

        if(oldHitCount+1 == newHitCount && oldMissCount+1 == newMissCount) {
            System.out.println("Came from DB");
        }  else if(oldHitCount+1 == newHitCount && oldMissCount == newMissCount) {
            System.out.println("Came from CACHE");
        }
        System.out.println("Entries in memory : " + sessionFactory.getStatistics().getSecondLevelCacheStatistics(rName).getEntries());

        sessionFactory.getStatistics().logSummary();

        return userSession;
    }

nice one !
you can add (kotlin style) :

@Autowired
lateinit var entityManager: EntityManager

it's not obvious from where your getEntityManager is coming from.