应用程序引擎Jruby数据映射器列表属性

如何在Google AppEngine上Jruby上的DataMapper中使用list/array作为属性？

这将像has..and..belling..to..many一样工作，没有联接表

class Person
  include DataMapper::Resource
  property :id,          Serial
  property :name,        String, :nullable => false
  property :project_ids, List
  timestamps :at
  # project should be flagged as archived, not deleted
  def projects
    Project.all(:id => project_ids)
  end
end

class Project
  include DataMapper::Resource
  property :id,          Serial
  property :name,        String, :nullable => false
  property :archived,    Boolean, :default => false
  # the join table is bolted onto the person model
  def people
    Person.all(:project_ids => id)
  end
end

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有没有关于在AppEngine上使用JRuby进行建模的不同方法的文档？