英文:
JPA @repository @Query Can handle a null entity?
问题
我正在使用 jpa 和 spring 完成一个项目，我需要执行类似这样的 query：
第一种写法：
Select models.dto.dealCalendarDTO(d, c) from deal d left outer join calendar c on calendar.deal_id=deal.id;
或者
第二种写法：
Select d,c from deal d left outer join calendar c on calendar.deal_id=deal.id;
当我尝试第一种写法时，出现了这个错误：java.lang.NullPointerException: null
当我使用第二种写法时，出现了这个错误：
Caused by: java.lang.IllegalStateException: No data type for node: org.hibernate.hql.internal.ast.tree.IdentNode
\-[IDENT] IdentNode: 'c' {originalText=c}
我使用传统的 SQL 进行了相同的操作而没有问题，但我觉得我可能漏掉了什么。
英文:
I am doing a project with jpa and spring , and i need to do a query like this:
Select models.dto.dealCalendarDTO(d, c) from deal d left outer join calendar c on calendar.deal_id=deal.id;
Or
Select d,c from deal d left outer join calendar c on calendar.deal_id=deal.id;
When I try the first one I have this error: java.lang.NullPointerException: null
When I use the second one, I have this one
Caused by: java.lang.IllegalStateException: No data type for node: org.hibernate.hql.internal.ast.tree.IdentNode
\-[IDENT] IdentNode: 'c' {originalText=c}
I did it with classic SQL without a problem, but I think I am missing something.
答案1
得分: 0
空指针异常出现在第一个查询中，因为你正在执行左连接，这可能会导致Calendar为null，而你在DTO函数中试图访问它。
英文:
The NullPointerException in the first query because you are doing a left join and this maybe cause that c Calendar will be null and you are trying to access it in the DTO function
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