public interface IDao<K, E> {

    /**
     * Performs SQL insert for the specified entity
     * @param entity domain object to store in database
     */
    void persist(E entity);

    /**
     * Performs SQL DELETE based on entity PK
     * @param id domain object to remove from database
     */
    void remove(K id);

    /**
     * Performs SQL SELECT with WHERE clause based in PK
     * @param id primary key attribute of entity
     * @return entity of type E with id of value of K
     */
    E findById(K id);

    /**
     * Performs SQL UPDATE for the specified entity
     * @param entity domain object to store in database
     */
    void update(E entity);
}

public class LicenseDao implements IDao<Integer, License> {

    private EntityManagerFactory entityManagerFactory;
    private EntityManager entityManager;
    private Logger logger = LoggerFactory.getLogger(LicenseDao.class);

    /**
     * JPA EntityManagerFactory instance injected, All other new parameters can should be injected similarly
     * to ensure compatibility with route controllers if extending this class.
     *
     * @param entityManagerFactory Injected by Jooby Framework IoC DI module
     */
    @Inject
    public LicenseDao(@Named("testPU") EntityManagerFactory entityManagerFactory) {
        this.entityManagerFactory = entityManagerFactory;
        this.entityManager = entityManagerFactory.createEntityManager();
    }

    /**
     * Performs SQL insert for the specified entity
     * @param entity domain object to store in database
     */
    @Override
    public void persist(License entity) {
        entityManager.getTransaction().begin();
        entityManager.persist(entity);
        entityManager.getTransaction().commit();
        entityManager.close();
    }

    /**
     * Performs SQL DELETE based on entity PK
     * @param id domain object to remove from database
     */
    @Override
    public void remove(Integer id) {
        entityManager.getTransaction().begin();
        License license = entityManager.find(License.class, id);
        if (license == null) {
            //Add notfication of failure
            logger.warn("Trying to remove non-exiting licence: " + id);
        } else {
            logger.info("Removing " + license);
            entityManager.remove(license);
        }
        entityManager.getTransaction().commit();
        entityManager.close();

    }

    /**
     * Performs SQL SELECT with WHERE clause based in PK
     * @param id primary key attribute of entity
     * @return entity of type E with id of value of K
     */
    @Override
    public License findById(Integer id) {
        return entityManager.find(License.class, id);
    }

    /**
     * Find all Licenses related to an organisation. Note that this will return all Licenses
     * and may be slow if large amount of Licenses exist.
     * @param organisationId organisation primary key used to relate conductor to organisation
     * @return List of Licenses
     */
    public List<License> findAllByOrganisationId(Integer organisationId) {
        EntityManager entityManager = entityManagerFactory.createEntityManager();

        return entityManager.
                createQuery(
                        "SELECT l from License l " +
                                "WHERE l.organisation.organisationId = :organisationId", License.class)
                .setParameter("organisationId", organisationId)
                .getResultList();
    }

    /**
     * Updates the license
     * @param license domain object to store in database
     */
    @Override
    public void update(License license) {
        entityManager.getTransaction().begin();
        entityManager.merge(license);
        entityManager.getTransaction().commit();
        entityManager.close();
    }

}