grails中的多个关联(Multiple associations in grails)

grails中的多个关联(Multiple associations in grails)

我有一个带有域名餐厅和域名人员的grails应用程序。

class Restaurant { String name static belongsTo = [ owner: Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant ] }

我的问题是GORM只创建了两个表，餐厅和人，餐厅有owner_id。 然而，我所缺少的是连接表，将一个人最喜欢的餐馆与他联系起来。

我可以理解为什么GORM这样做（双向一对多），但是我无法弄清楚如何以我想要的方式做到这一点（1x单向一对多，1x单向多对一） 。 我想我应该使用mappedBy，但我不知道要映射到什么，因为没有什么可以链接回来:-(

此外，我最初考虑以下域名：

class Restaurant { String name static belongsTo = [ owner: Person ] static hasMany = [ outstandingCouponOwners : Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant ] }

哪里有另一个一对多的关系（再一次没有把它映射到另一端）

I have a grails app with a domain Restaurant and a domain Person.

class Restaurant { String name static belongsTo = [ owner: Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant ] }

My problem is that GORM creates only two tables, Restaurant and Person, where Restaurant has an owner_id. However what I am missing is the join table that links a person's favorite restaurants back to him.

I can understand why GORM does it this way (bidirectional one-to-many), however I can't figure out how to do it the way I want (1x unidirection one-to-many, 1x unidirectional many-to-one). I guess I should use mappedBy but I do not know what to map it to as there is nothing linking it back :-(

Additionally, I was initially considering the following domains:

class Restaurant { String name static belongsTo = [ owner: Person ] static hasMany = [ outstandingCouponOwners : Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant ] }

where there is another one-to-many relationship (and again with nothing to map it to on the other end)

最满意答案

我想，你必须使用域类的'mappedBy'静态映射。 有关详细信息，请参阅grails参考指南的5.2.1.2部分的底部。 可能有必要在Person的hasMany中引入其他条目：该人拥有的餐馆列表。 尝试以下（完全未经测试的）代码：

class Restaurant { String name static belongsTo = [ owner: Person ] static hasMany = [ outstandingCouponOwners : Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant, owns: Restaurant, coupons: Restaurant ] static mappedby = [ owns: 'owner', coupons: 'outstandingCouponOwners' ] }

I think, you have to use the 'mappedBy' static map of a domain class. For details look at the bottom of section 5.2.1.2 of the grails reference guide. It might be necessary to introduce additional entries in Person's hasMany: the list of restaurants owned by the person. Try the following (completely untested) code:

class Restaurant { String name static belongsTo = [ owner: Person ] static hasMany = [ outstandingCouponOwners : Person ] } class Person { String name static hasMany = [ favoriteRestaurants : Restaurant, owns: Restaurant, coupons: Restaurant ] static mappedby = [ owns: 'owner', coupons: 'outstandingCouponOwners' ] }