private static void updateArticle() {
System.out.println("-- updating article --");
EntityManager em = entityManagerFactory.createEntityManager();
Article article = em.find(Article.class, 1L);
em.getTransaction().begin();
em.lock(article, LockModeType.OPTIMISTIC_FORCE_INCREMENT);
if (article.getContent().length() < 5) {
article.setContent("updated content");
}
em.getTransaction().commit();
em.close();
System.out.println("Article updated : " + article);
}