将摘录投影添加到 Spring Data Rest 存储库会导致堆栈溢出错误

Question

当我们在 REST 存储库上启用 except 投影时，我们将面临 StackoverflowError。实体是问题有两个关联，一个@ManyToOne 与一个Venue 实体必须包含在所有响应的内联中，以及一个@OneToMany 与Trainee 实体我们总是想隐藏。实体（相关）sn-p

@Entity
@EntityListeners(AuditingEntityListener.class)
public class Workshop implements Serializable {

  private static final long serialVersionUID = -5516160437873476233L;

  private Long id;

  // omitted properties

  private Venue venue;

  private Set<Trainee> trainees;

  @Id
  @GeneratedValue
  public Long getId() {
    return id;
  }

  @ManyToOne(fetch = FetchType.EAGER)
  @JoinTable(name = "workshop_venue", joinColumns = { @JoinColumn(name = "workshop_id", referencedColumnName = "id") }, inverseJoinColumns = { @JoinColumn(name = "venue_id", referencedColumnName = "id") })
  public Venue getVenue() {
    return venue;
  }

  @OneToMany
  @JoinTable(name = "workshop_trainees", joinColumns = { @JoinColumn(name = "workshiop_id", referencedColumnName = "id") }, inverseJoinColumns = { @JoinColumn(name = "trainee_id", referencedColumnName = "email") })
  @RestResource(exported = false)
  @JsonIgnore
  public Set<Trainee> getTrainees() {
    return trainees;
  }

  // omitted getters/setters
}

当我添加这个投影时

@Projection(name = "default", types = { Workshop.class })
public interface InlineVenueProjection {

  String getName();

  Integer getSeatsAvailable();

  WorkshopType getWorkshopType();

  Date getDate();

  Venue getVenue();
}

并在存储库中启用它

@RepositoryRestResource(collectionResourceRel = "workshop", path = "workshops", excerptProjection = InlineVenueProjection.class)
public interface WorkshopRepository extends JpaRepository<Workshop, Long> {
// omitted methods
}

我在 POST 请求中遇到堆栈溢出错误

org.springframework.web.util.NestedServletException: Handler processing failed; nested exception is java.lang.StackOverflowError

在堆栈跟踪中进一步

Caused by: java.lang.StackOverflowError: null
    at java.util.concurrent.locks.ReentrantReadWriteLock$Sync$ThreadLocalHoldCounter.initialValue(ReentrantReadWriteLock.java:286)
    at java.lang.ThreadLocal.setInitialValue(ThreadLocal.java:180)
    at java.lang.ThreadLocal.get(ThreadLocal.java:170)
    at java.util.concurrent.locks.ReentrantReadWriteLock$Sync.tryReleaseShared(ReentrantReadWriteLock.java:423)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.releaseShared(AbstractQueuedSynchronizer.java:1341)
    at java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.unlock(ReentrantReadWriteLock.java:881)
    at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:169)
    at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:140)
    at org.springframework.data.mapping.context.AbstractMappingContext.getPersistentEntity(AbstractMappingContext.java:67)
    at org.springframework.data.mapping.context.PersistentEntities.getPersistentEntity(PersistentEntities.java:63)
    at org.springframework.data.rest.webmvc.mapping.LinkCollectingAssociationHandler.doWithAssociation(LinkCollectingAssociationHandler.java:100)
    at org.springframework.data.mapping.model.BasicPersistentEntity.doWithAssociations(BasicPersistentEntity.java:352)

Answer 1

您收到堆栈溢出异常的原因是因为我猜Venue (1-Many) 和 Workshop (Many-1) 之间定义了双向关系。你可以证实我的假设。

当您尝试直接序列化场所时，因为关系研讨会已加载并且它具有对场所的引用，因此无休止的递归。

解决方案

为了解决这个问题，Jackson 有@JsonManagedReference 和@JsonBackReference。

工作坊课堂

public class Workshop implements Serializable {
    ...

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinTable(name = "workshop_venue", joinColumns = { @JoinColumn(name = "workshop_id", referencedColumnName = "id") }, inverseJoinColumns = { @JoinColumn(name = "venue_id", referencedColumnName = "id") })
    @JsonManagedReference
    public Venue getVenue() {
        return venue;
    }

    ...
}

场地课

public class Venue implements Serializable {
    ...

    @OneToMany
    @JsonBackReference
    public List<Workshop> getWorkshops() {
        return workshops;
    }

    ...
}

希望这会有所帮助。让我知道这是否有效。