java 如何将连接查询映射到 JPA 中的非实体类？
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How to map join query to non-entity class in JPA?
提问by zawhtut
In hibernate
处于休眠状态
Join queries can be mapped with non-entity class . How to map a database query into an Object [in Java]?
连接查询可以映射到非实体类。如何将数据库查询映射到对象 [在 Java 中]？
<class name=... select="select A.field_a, B.field_b, ... from A, B, ...">
How can I achieve the same thing in JPA/Hibernate ?
我怎样才能在 JPA/Hibernate 中实现同样的事情？
回答by Affe
In hibernate you can invoke a constructor of any arbitrary class inside the select clause of a query.
在休眠中，您可以在查询的 select 子句中调用任意类的构造函数。
@NamedQuery( name = "myScalarQuery" query =
"select new org.stackoverflow.hibernate.QueryResultObject(A.field_a, B.field_b)
from A, B
where a.someUsefulProperty = b.someComparableProperty")
etc. (note fully qualified classname is required)
等（注意需要完全限定的类名）
Then you just need the class the has a matching constructor
然后你只需要具有匹配构造函数的类
public class QueryResultObject {
public QueryResultObject(TypeOfFieldA fieldA, TypeOfFieldB fieldB) {
//etc
}
}
