Spring JPA 锁定概念

Posted 2023-02-26

【中文标题】Spring JPA 锁定概念

【英文标题】：Spring JPA Locking Concept

【发布时间】：2020-01-15 07:05:48

【问题描述】：

有人知道如何在 Spring JPA 中使用 Locking with UPDATE 语句，以便一次只能一个线程更新记录吗？

在这里，我正在尝试更新表名 aircraft_route 的可用性，并且在更新之前，我想获取该行的锁定，以便没有其他线程可以同时更新它。

错误：非法尝试在本机 SQL 查询上设置锁定模式

任何帮助将不胜感激。

谢谢

AirCraftRoute.java

@Builder
@Setter
@Getter
@AllArgsConstructor
@NoArgsConstructor
@Entity(name = "aircraft_route")
public class AirCraftRoute implements Serializable

    @EmbeddedId
    private AirCraftRoutePK pk = new AirCraftRoutePK();

    @ManyToOne
    @MapsId("airCraftId")
    @JoinColumn(name = "aircraft_id")
    private AirCraft airCraft;

    @ManyToOne
    @MapsId("routeId")
    @JoinColumn(name = "route_id")
    private Route route;

    @Column(name = "journey_date")
    private Date journeyDate;

    @Column(name = "departure_time")
    private Time departureTime;

    @Column(name = "arrival_time")
    private Time arrivalTime;

    @Column(name = "fare")
    private float fare;

    @Column(name = "availability")
    private int availability;

    @Override
    public boolean equals(Object o) 
        if (this == o) return true;
        if (!(o instanceof AirCraftRoute)) return false;
        AirCraftRoute that = (AirCraftRoute) o;
        return Float.compare(that.getFare(), getFare()) == 0 &&
                Objects.equals(getAirCraft(), that.getAirCraft()) &&
                Objects.equals(getRoute(), that.getRoute()) &&
                Objects.equals(getJourneyDate(), that.getJourneyDate()) &&
                Objects.equals(getDepartureTime(), that.getDepartureTime()) &&
                Objects.equals(getArrivalTime(), that.getArrivalTime());
    

    @Override
    public int hashCode() 
        return Objects.hash(getAirCraft(), getRoute(), getJourneyDate(), getDepartureTime(), getArrivalTime(), getFare());
    

AirCraftRouteRepository.java

@Repository
public interface AirCraftRouteRepository extends JpaRepository<AirCraftRoute,Integer> 

    @Transactional
    @Query(value = "SELECT ar.availability FROM aircraft_route ar WHERE ar.aircraft_id = :airCraftId AND ar.route_id = :routeId FOR UPDATE",nativeQuery = true)
    int getAvailability(@Param("airCraftId") Long airCraftId, @Param("routeId") Long routeId);

    @Modifying
    @Transactional
    @Lock(LockModeType.PESSIMISTIC_WRITE)
    @Query(value = "UPDATE aircraft_route ar SET ar.availability = ar.availability - :numberOfTickets WHERE ar.aircraft_id = :airCraftId AND ar.route_id = :routeId AND ar.availability > 0",nativeQuery = true)
    int updateAvailability(@Param("numberOfTickets") int numberOfTickets,@Param("airCraftId") Long airCraftId, @Param("routeId") Long routeId);

【参考方案1】：

我认为对于本机 SQL，您根本不需要 Lock。您可以直接在原生查询中FOR UPDATE。像这样

@Transactional
@Query(value = "SELECT * FROM aircraft_route ar WHERE ar.aircraft_id = :airCraftId AND ar.route_id = :routeId FOR UPDATE",nativeQuery = true)
List<Integer> getAvailability(@Param("airCraftId") Long airCraftId, @Param("routeId") Long routeId);

【讨论】：

知道如何在 UPDATE 命令中使用“FOR UPDATE”吗？ @Query(value = "UPDATE aircraft_route ar SET ar.availability = ar.availability - :numberOfTickets WHERE ar.aircraft_id = :airCraftId AND ar.route_id = :routeId AND ar.availability > 0",nativeQuery = true) 我们可以使用 UPDATE使用上述命令？

更新时无需使用FOR UPSATE。你已经在更新了。

【参考方案2】：

我认为您可以简单地避免对这种简单语法使用本机查询：

@Transactional
@Lock(LockModeType.PESSIMISTIC_WRITE)
@Query(value = "SELECT * FROM AircraftRoute ar WHERE ar.id = :airCraftId AND ar.routeId = :routeId")
List<Integer> getAvailability(@Param("airCraftId") Long airCraftId, @Param("routeId") Long routeId);

类似上面的东西。您必须对实体名称和字段使用正确的语法，然后您可以使用 @Lock Spring 注释及其数据库锁管理，而不是手动处理。

【讨论】：

您的解决方案抛出异常，因为“方法 public abstract java.util.List com.abc.gds.repository.AirCraftRouteRepository.getAvailability 的查询验证失败”，我认为，这是由于： ***.com/questions/44647630/…

你能发布你的 AircraftRoute 实体吗？以及更新的接口getAvailability方法？