GRAILS GORM 如何在保存子项时自动更新父项属性

Question

我有两个对象。

TimeFrame{

  hasMany=[activity:Activity]

   Date startTime
   Date endTime
   Integer activeActivities

}

Activity{
   belongsTo=[timeFrame:TimeFrame]

  String name
  String description
  Date start
  Date end

}

每当我插入、更新或删除一个 Activity 我想自动更新一个时间范围内的 activeActivities 的数量。但是当我添加 GROM 事件方法时...

def afterUpdate(){
    try{

        def num=0;
        def now=new Date();
        timeFrame.activities.each{i->
            if(!i.end || i.end < now){
                num+=1;
            }
        }
        timeFrame.activeActivities=num;
        timeFrame.save();
    }
    catch(e){
        log.debug('Unable to update active tally on Activity update:'+e)
    }
}

我收到错误

  null id in com.application.tracker.Activity entry (don't flush the Session after an exception occurs).

有什么解决办法？

Answer 1

你的 save 在你的 afterUpdate 中失败的原因是你没有使用 withNewSession。 documentation 指出了这个细节。

Notice the usage of withNewSession method above. Since events are triggered whilst Hibernate is flushing using persistence methods like save() and delete() won't result in objects being saved unless you run your operations with a new Session.

Fortunately the withNewSession method lets you share the same transactional JDBC connection even though you're using a different underlying Session.

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