如何在Grails中通过jointable来加载关联类?

换句话说,以下内容:

class Subscriber { 
    ... 
    static hasMany = [ topics : Topic] 
    static fetchMode = [topics:"eager"] 

    static mapping = { 
        topics joinTable: [name: 'subscriber_topic', column: 'topic_id', key: 'subscriber_id']  
    } 
} 

急切地加载join table subscriber_topic,但不加载SQL日志中看到的topic类:

Hibernate: 
    select 
        subscriber0_.id as id41_0_, 
        subscriber0_.version as version41_0_, 
        .... 
        topics2_.subscriber_id as subscriber1_3_, 
        topics2_.topic_id as topic2_3_ 
    from 
        subscriber subscriber0_ 
    left outer join 
        subscriber_topics topics2_ 
            on subscriber0_.id=topics2_.subscriber_id 
    where 
        subscriber0_.id=? 

我希望实际获取的主题对象——而不是联接表。但是,似乎提取发生在联接表上,而不是实际关联的对象上。