Grails domain class relationship to itself

I need a way to be able to have a domain class to have many of itself. In other words, there is a parent and child relationship. The table I'm working on has data and then a column called "parent_id". If any item has the parent_id set, it is a child of 开发者_运维问答that element.

Is there any way in Grails to tell hasMany which field to look at for a reference?

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This is an example of what you are looking for (it's a snippet code I am running and it generates column parent_id). I don't think you need SortedSet:

class NavMenu implements Comparable { 
    String category
    int rank = 0

    String title
    Boolean active = false

    //NavMenu parent
    SortedSet subItems
    static hasMany = [subItems: NavMenu]
    static belongsTo = [parent: NavMenu]
  }

Furthermore, you can give name to the hasMany clause using the Mapping DSL, which is explained at http://grails.org/GORM+-+Mapping+DSL