Hibernate save或者persist 后获取主键ID

一个自增长ID的对象被save或者persist后，会返回其主键ID：

        Department department = new Department();
        department.setName("xxxxxxx");
        session.persist(department);
        System.out.println("id = " + department2.getId());

        Department department2 = new Department();
        department2.setName("xxxxxxx");
        session2.save(department2);
        System.out.println("id2 = " + department2.getId());

这两种方式都能获取一个主键自增长对象的持久化后的主键