等同于ActiveRecord的has_many的Hibernate:through [英] Hibernate equivalent of ActiveRecord's has_many :through

问题描述

在Rails中，可以声明一个传递关系，如下所示:

In Rails it is possible to declare a transitive relation as follows:

class Author < ActiveRecord::Base
    has_many :authorships
    has_many :books, :through => :authorships
end

是否可以在Hibernate中执行类似的操作?当我打电话给author.getBooks()时，我希望Hibernate知道与具有本书著作权的作者一起加入.

Is it possible to do something similar in Hibernate? When I call author.getBooks() I want Hibernate to know to join authors with authorships with books.

推荐答案

我不相信Hibernate的映射中可以完成任何操作，但是您可以在Author类中简单地添加一个getBooks()方法，在authorships属性上调用正确的方法:

I don't believe there is anything in Hibernate's mappings that can accomplish this, but you could simply add a getBooks() method to your Author class that calls the correct method on the authorships property:

public class Author {
    public Collection<Book> getBooks() {
        if (this.authorships != null) {
            return this.authorships.getBooks();
        }
        return null;    
    }
}

如果您可以自己在类中进行设置，我不确定为什么ORM需要知道A与C之间的传递关系.

I'm not sure why the ORM would need to know about a transitive relationship between A and C between B, if you can just set that up in the class on it's own.

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