Hibernate标准顺序依据 [英] Hibernate Criteria Order By

问题描述

我有一张名为Gift的表格，它与一个名为ClickThrough的表格有一对多的关系 - 表示特定礼物被点击了多少次。我需要查询所有Gift对象，按ClickThrough计数排序。我不需要返回的ClickThrough计数，因为我不需要做任何事情，我只是想用它来订购。

我需要查询直接返回礼物对象列表，只需按ClickThrough计数排序即可。我如何使用Criteria API来做到这一点？我可以在这里找到很多有关此类信息的文档，但没有什么比我需要的更多。 解决方案

如果你想要返回一个实体或属性列表，以及您将需要分组的计数。在标准中，这通过 ProjectionList 和 Projections 完成。例如

  final ProjectionList props = Projections.projectionList（）; 
 props.add（Projections.groupProperty（giftID））; 
 props.add（Projections.groupProperty（giftName））; 
 props.add（Projections.count（giftID），count）; //为计数创建一个别名
 crit.setProjection（道具）; 
 
 crit.add（Order.desc（count））; //使用计数别名来命令
  

但是，由于您使用 ProjectionList 您还需要使用 AliasToBeanConstructorResultTransformer 。

I have a table called Gift, which has a one-to-many relationship to a table called ClickThrough - which indicates how many times that particular Gift has been clicked. I need to query for all of the Gift objects, ordered by ClickThrough count. I do not need the ClickThrough count returned, as I don't need anything done with it, I just want to use it for purposes of ordering.

I need the query to return a List of Gift objects directly, just ordered by ClickThrough count. How do I do this using the Criteria API? I can find a lot of documentation out there on similar information to this, but nothing quite like what I need.

解决方案

If you want to return a list of entities or properties in combination with a count you will need a group by. In criteria this is done through ProjectionList and Projections. e.g.

    final ProjectionList props = Projections.projectionList();
    props.add(Projections.groupProperty("giftID"));
    props.add(Projections.groupProperty("giftName"));
    props.add(Projections.count("giftID"), "count"); //create an alias for the count
    crit.setProjection(props);

    crit.add(Order.desc("count")); //use the count alias to order by

However, since you're using ProjectionList you will also need to use AliasToBeanConstructorResultTransformer.

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