JPA - EntityManager.contains Examples

    private static void logPersistentStatus(String msg, Employee employee, EntityManager em) {
        System.out.printf("-- %s --%n", msg);
        System.out.println("employee#id: " + employee.getId());
        System.out.println("EntityManager#contains(): " + em.contains(employee));
    }

    private static void persistEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = new Employee("Sara", "Admin");
        System.out.println("New entity: " + em.contains(employee));
        em.getTransaction().begin();
        em.persist(employee);
        System.out.println("After EntityManager.persist() : " + em.contains(employee));
        em.getTransaction().commit();
        System.out.println("After commit: " + em.contains(employee));
        em.close();
    }

    private static void persistEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = new Employee("Joe", "IT");
        em.getTransaction().begin();
        em.persist(employee);
        em.getTransaction().commit();
        em.close();
        System.out.println("After EntityManager.close(): " + em.contains(employee));
    }

    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 findByGetReference() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.getReference(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 findByReferenceAndRemoveEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.getReference(Employee.class, 1);
        System.out.println("after getReference(): " + 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 findByReferenceAndDetachEntity() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.getReference(Employee.class, 1);
        System.out.println("after getReference(): " + 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 findByRefDetachAndMerge() {
        EntityManager em = entityManagerFactory.createEntityManager();
        Employee employee = em.getReference(Employee.class, 1);
        System.out.println("after getReference(): " + em.contains(employee));
        em.detach(employee);
        System.out.println("after detach(): " + em.contains(employee));
        employee = em.merge(employee);
        System.out.println("after merge(): " + em.contains(employee));
        em.close();
    }

    private static Employee checkAndInitialize(Employee employee) {
        PersistenceUtil pu = entityManagerFactory.getPersistenceUnitUtil();
        System.out.println("       Employee loaded: " + pu.isLoaded(employee));
        System.out.println("Employee.phones loaded: " + pu.isLoaded(employee, "phones"));
        if (!pu.isLoaded(employee) //entity might've been retrieved via getReference
                || !pu.isLoaded(employee, "phones")//phones is a lazy relation
                ) {
            System.out.println("initializing employee");
            boolean detached = !entityManager.contains(employee);
            System.out.println("is employee detached: " + detached);
            if (detached) {
                System.out.println("merging employee");
                employee = entityManager.merge(employee);
            }
            //this will load/initialize employee entity
            employee.getName();
            employee.getDepartment();
            //this will load lazy phones field
            employee.getPhones().size();
            entityManager.detach(employee);
            //now employee is fully initialized
            System.out.println("employee initialized");
        }
        return employee;
    }