Question

我确实有3个实体，想要交叉加入它们。由于我不需要为此创建新的实体，我只想通过使用本机查询来获取：

EntityA{
    ...
    String someValue;
}

EntityB{
    ...
    String someValue;
}

EntityC{
    ...
    String someValue;
}

和CrossJoined对象

CrossJoinedFoo{
    EntityA entityA;
    EntityB entityB;
    EntityC entityC;
}

我正在使用它：

private static final String _SELECT_CROSS_JOIN_ENTITIES = "SELECT * FROM "
            + "EntityA"
            + ", "
            + "EntityB"
            + ", "
            + "EntityC"
            + " WHERE (1=1) "
            + " AND " + "EntityA.someValue = :someValue"
            + " AND " + "EntityB.someValue = :someValue"
            + " AND " + "EntityC.someValue = :someValue";

Query query = entityManager.createNativeQuery(_SELECT_CROSS_JOIN_ENTITIES);
query.setParameter(":someValue", "foo");

我该如何实现这种行为？

Answer 1

您可以使用HQL查询并使用结果类策略。只需记住向CrossJoinedFoo添加一个构造函数，以适当的顺序接受3个实体：

private static final String _SELECT_CROSS_JOIN_ENTITIES = 
            "SELECT new my.package.CrossJoinedFoo(a,b,c) FROM "
            + "EntityA a"
            + ", "
            + "EntityB b"
            + ", "
            + "EntityC c"
            + " WHERE (1=1) "
            + " AND " + "a.someValue = :someValue"
            + " AND " + "b.someValue = :someValue"
            + " AND " + "c.someValue = :someValue";

Query query = entityManager.createQuery(_SELECT_CROSS_JOIN_ENTITIES);
query.setParameter(":someValue", "foo");

List<CrossJoinedFoo> result = query.list();

请记住将包更改为合适的包。

Answer 2

将@SqlResultSetMapping与@ConstructorResult

一起使用

请注意，结果实体不会成为managed

Hibernate / JPA映射本地查询到非实体持有实体的结果

2 个答案: