如何将连接查询映射到JPA中的非实体类? [英] How to map join query to non-entity class in JPA?
本文介绍了如何将连接查询映射到JPA中的非实体类?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
连接查询可以映射为非实体类。 如何映射数据库查询转换成Java的对象?
< class name = ... select =select A. field_a,B.field_b,... from A,B,...>
如何在JPA / Hibernate中实现同样的功能?
<在hibernate中,你可以在查询的select子句中调用任意类的构造函数。
@NamedQuery(name =myScalarQueryquery =
select new org.stackoverflow.hibernate.QueryResultObject(A.field_a,B.field_b)
from A,B
其中a.someUsefulProperty = b.someComparableProperty)
等。 (请注意完全限定的类名)
然后你只需要该类有一个匹配的构造函数
public class QueryResultObject {
public QueryResultObject(TypeOfFieldA fieldA,TypeOfFieldB fieldB){
// etc
}
}
In hibernate
Join queries can be mapped with non-entity class . How to map a database query into an Object [in Java]?
<class name=... select="select A.field_a, B.field_b, ... from A, B, ...">
How can I achieve the same thing in JPA/Hibernate ?
解决方案
In hibernate you can invoke a constructor of any arbitrary class inside the select clause of a query.
@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)
Then you just need the class the has a matching constructor
public class QueryResultObject {
public QueryResultObject(TypeOfFieldA fieldA, TypeOfFieldB fieldB) {
//etc
}
}
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