休眠一对一（在外键上）与一对一（在主键上）

除了JB Nizet提到的优点之外，还有一个人告诉我，基于外键的一对一比较灵活。让我们考虑我对外键（用户< ---外围）使用一对一，如果应用程序的需求变化需要多个用户的任何外围，如果我共享主键，我会重构要做得更多。但是，当我使用外键时，我所做的只是放松唯一的约束;）

i have questions about what is the benefits of using a one-to-one association on foreign key or a one-to-one association on primary key, I've read the documentation of hibernate available at : docs.jboss/hibernate/orm/3.3/reference/en/html/associations.html#assoc-unidirectional-121 can someone tell me with details the plus of using the first or the second implementation?

another question, i'have a one-to-one unidirectional relationship between User and Perimeter (User ----> Perimeter) and i want to use the association based on the foreign key. could i reverse the direction into (User <---- Perimeter) so the table User stay intact? I think that is not reasonable (perimeter.getUser() !!!) but it's technically possible?

In addition to advantages mentioned by JB Nizet and thanks to another person told me that the one-to-one based on foreign key is more flexible. let's consider that i use a one-to-one on foreign key (User <--- Perimeter) , if the requirements of the application changes to need multiple Users for any Perimeter, If i shared the primary key, I'll have much more refactoring to do. But as i used the foreign key, all i do is relax the unique constraint ;)