java 休眠，获取重复值
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Hibernate, getting duplicate values
提问by Shervin Asgari
I am writing a very simple query, but I am getting duplicate values for some reason.
我正在编写一个非常简单的查询，但由于某种原因我得到了重复的值。
Criteria cr = session.createCriteria(ProcessInstance.class, "p")
.add(Restrictions.isNull("end"));
@Cleanup ScrollableResults sr = cr.scroll(ScrollMode.FORWARD_ONLY);
while (sr.next()) {
pi = (ProcessInstance) sr.get(0);
String id = pi.getId(); //Getting duplicate values
}
The pi.getId()returns duplicate values. ie: *9,9,10,10,11,11 etc*
在pi.getId()返回重复值。IE：*9,9,10,10,11,11 etc*
However, running this query directly in mysql
但是，直接在 mysql 中运行此查询
SELECT * FROM JBPM_PROCESSINSTANCE J where J.END_ IS NULL
Does not return duplicate values.
不返回重复值。
Can anyone spot what is wrong?
任何人都可以发现有什么问题吗？
回答by Ralph
The fast workarround would be to use a Distinct Root Entity Result Transformer.
快速解决方法是使用不同的根实体结果转换器。
...
crit.setResultTransformer(CriteriaSpecification.DISTINCT_ROOT_ENTITY);
List unique = crit.List();
...
But this is only a workarround.
但这只是一种解决方法。
I ques the problem belongs to your mapping. If there is any eager loaded 1:n relationship from ProcessInstance to something else (call it X), and there are several (n) X for one ProcessInstance, the you will get several ProcessInstance items (n) in the result list for a single ProcessInstance. -- If this is realy the cause, than the workarround is not just a workarround, then it would be the solution.
我问这个问题属于你的映射。如果从 ProcessInstance 到其他东西（称为 X）存在任何预先加载的 1:n 关系，并且一个 ProcessInstance 有多个 (n) X，那么您将在结果列表中获得多个 ProcessInstance 项 (n) 以获取单个进程实例。-- 如果这确实是原因，那么 workarround 不仅仅是 workarround，那么它就是解决方案。
回答by seesee
I encouter the same problem as you..
我遇到和你一样的问题..
This is how I solve it.
这就是我解决它的方法。
Criteria cr = session.createCriteria(ProcessInstance.class, "p")
.add(Restrictions.isNull("end")).setProjection("id")
this will returns all the ID that satisfy all your criteria.
这将返回满足所有条件的所有 ID。
there after you use Inrestrictions and perform CriteriaSpecification.DISTINCT_ROOT_ENTITY.
在您使用In限制并执行CriteriaSpecification.DISTINCT_ROOT_ENTITY.
You will be able to scroll your result in 2nd criteria.. I hope this help.
您将能够在第二个条件中滚动您的结果.. 我希望这会有所帮助。
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