java - 使用 JPA 关系查询时非法尝试取消引用集合

Question

我有 2 个类:

@Table(name = "PEOPLE")
@Entity
class Person {
  @OneToMany(mappedBy = "owner")
  Set<Car> cars;
}
@Table(name = "CARS")
@Entity
class Car {
  @ManyToOne
  @JoinColumn(name = "OWNER_ID", referencedColumnName = "ID")
  Person owner;
  @Column(name = "MODEL")
  String model;
}

我正在尝试按模型查询人员。运行以下代码失败，即使表之间的联系很清楚:

select mo from Person mo where mo.cars.model = ?

错误是:

org.hibernate.QueryException: illegal attempt to dereference collection [...] with element property reference [model] [select mo from Person mo where mo.cars.model = ?]

知道如何解决这个问题吗？

Answer 1

当实体之间的关系已经定义好后，可以使用join fetch语法:

select mo from Person mo join fetch mo.cars c where c.model = ?