java - 如何正确实现涉及两个表之间 JOIN 的 Spring Data JPA 命名查询？

Question

我正在使用 Spring Data JPA 开发 Spring 应用程序。我实现了命名查询方法来实现我的查询。我在尝试实现涉及 2 个表\实体类之间的联接的命名查询时遇到一些困难。

所以我有这两个实体类:

1) Room 代表住宿的房间:

@Entity
@Table(name = "room")
public class Room implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @ManyToOne
    @JoinColumn(name = "id_accomodation_fk", nullable = false)
    private Accomodation accomodation;

    @ManyToOne
    @JoinColumn(name = "id_room_tipology_fk", nullable = false)
    private RoomTipology roomTipology;

    @Column(name = "room_number")
    private String number;

    @Column(name = "room_name")
    private String name;

    @Column(name = "room_description")
    @Type(type="text")
    private String description;

    @Column(name = "max_people")
    private Integer maxPeople;

    @Column(name = "is_enabled")
    private Boolean isEnabled;

    // CONSTRUCTOR, GETTER AND SETTER METHODS
}

正如你所看到的，这个类包含这个字段:

@ManyToOne
@JoinColumn(name = "id_room_tipology_fk", nullable = false)
private RoomTipology roomTipology;

将许多 Room 实例链接到 RoomTipology 实例。

2)然后我有RoomTipology实体类:

@Entity
@Table(name = "room_tipology")
public class RoomTipology implements Serializable{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @Column(name = "tipology_name")
    private String name;

    @Column(name = "tipology_description")
    private String description;

    @Column(name = "time_stamp")
    private Date timeStamp;

    @OneToMany(mappedBy = "roomTipology")
    private List<Room> rooms;

    @OneToOne(mappedBy = "roomTipology")
    private RoomRate roomRate;

    // CONSTRUCTOR, GETTER AND SETTER METHODS
}

然后我有 RoomTipology 实体类的存储库类，如下所示:

@Repository
@Transactional(propagation = Propagation.MANDATORY)
public interface RoomTipologyDAO extends JpaRepository<RoomTipology, Long> {

    RoomTipology findByRoomTipology_Room(Room room);

}

我已经尝试过这种方式，但它不起作用，并且收到以下错误消息:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'roomTipologyDAO': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property roomTipology found for type RoomTipology!

我想从Room开始检索相关的RoomTipology实例。基本上我想将此 SQL 查询转换为 Spring Data JPA 命名查询:

SELECT * 
FROM `room_tipology` rt 
INNER JOIN room r
ON rt.id = r.id_room_tipology_fk
WHERE r.id = 7

其中 r.id 是 Room 实体的 id 字段的值。

我知道，如果我已经有一个 Room 对象，我可以通过以下方式获取此信息:

room.getRoomTipology()

但有时我只有 Room 实例的 ID，我想直接检索相关的 RoomTipology 对象。

如何使用命名查询来做到这一点？

Answer 1

按照您认为最好的方式命名您的方法，传递 roomId 而不是房间，因为那是您的实际搜索参数，并使用注释该方法

@Query("select t from Room r join r.roomTypology t where r = :roomId")