Grails中的多个关联 [英] Multiple associations in grails

问题描述

我有一个带域名Restaurant和域名Person的grails应用程序。

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 ]
}

我的问题是GORM只创建两个表，Restaurant和Person，其中Restaurant有owner_id。然而，我所缺少的是连接一个人最喜欢的餐馆的连接表。

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.

我可以理解GORM为什么这样做（双向一对多），但我无法弄清楚如何以我想要的方式进行操作（1x单向一对多，1x单向多对一）。我想我应该使用 mappedBy ，但我不知道是什么将其映射为没有任何链接返回： - （

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 :-(

另外，我最初考虑了以下域：

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 ]
}

哪里有另一个一对多的关系（并且没有任何关系可以将它映射到另一端）

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

推荐答案

我认为，您必须使用domain类的'mappedBy'静态映射。有关详细信息，请查看 grails参考指南的第5.2.1.2节。
可能需要在Person的hasMany中添加更多条目：该人拥有的餐馆列表。尝试以下（完全未经测试）代码：

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' ]
}

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