JPA - EntityManager.find Examples

    private static void removeEntity(EntityManagerFactory emf, int id) {
        EntityManager em = emf.createEntityManager();
        Employee employee = em.find(Employee.class, id);
        System.out.println("-- removing entity --");
        printObject(employee);

        em.getTransaction().begin();
        em.remove(employee);
        em.getTransaction().commit();
        em.close();
    }

    private static Employee loadEmployeeById(int id) {
        System.out.println("-- loading employee by id --");
        EntityManager em = emf.createEntityManager();
        return em.find(Employee.class, id);
    }

    private static Person loadPersonById(long id) {
        EntityManager em = emf.createEntityManager();
        Person person = em.find(Person.class, id);
        em.close();
        return person;
    }

    private static Person loadPersonById(long id) {
        EntityManager em = emf.createEntityManager();
        Person person = em.find(Person.class, id);
        em.close();
        return person;
    }

    private static void updateByFinding(EntityManagerFactory emf) {
        System.out.println("-- updating employee by finding --");
        EntityManager em = emf.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        em.getTransaction().begin();
        System.out.println("-- setting new name -- ");
        employee.setName("Diana");
        System.out.println("-- committing --");
        em.getTransaction().commit();
        em.close();
    }

    private static void findEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        System.out.println("after find(): " + em.contains(employee));
        em.close();
    }

    private static void findAndRemoveEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        System.out.println("after find(): " + em.contains(employee));
        em.remove(employee);
        System.out.println("after remove(): " + em.contains(employee));
        em.close();
    }

    private static void findAndDetachEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        System.out.println("after find(): " + em.contains(employee));
        em.detach(employee);
        System.out.println("after detach(): " + em.contains(employee));
        em.close();
    }

    private static void findDetachAndMergeEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.find(Employee.class, 1);
        System.out.println("after find(): " + em.contains(employee));
        em.detach(employee);
        System.out.println("after detach(): " + em.contains(employee));
        employee = em.merge(employee);
        System.out.println("after merging(): " + em.contains(employee));
        em.close();
    }

    private static void updateArticle() {
        log("updating Article entity");
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        Article article = em.find(Article.class, 1L, LockModeType.PESSIMISTIC_WRITE);
        try {
            TimeUnit.SECONDS.sleep(2);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        article.setContent("updated content .. ");
        log("committing in write thread.");
        em.getTransaction().commit();
        em.close();
        log("Article updated", article);
    }

    private static void readArticle() {
        log("before acquiring read lock");
        EntityManager em = entityManagerFactory.createEntityManager();
        em.getTransaction().begin();
        Article article = em.find(Article.class, 1L, LockModeType.PESSIMISTIC_READ);
        log("After acquiring read lock", article);
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        em.getTransaction().commit();
        em.close();
        log("Article after read commit", article);
    }