Micronaut 数据问题懒惰地获取相关实体答案

【问题标题】：Micronaut data problem lazily fetching related entitiesMicronaut 数据问题懒惰地获取相关实体
【发布时间】：2021-01-21 13:06:36
【问题描述】：

我目前正在将 micronaut 数据合并到现有的 micronaut 项目中（作为升级的一部分），并且在延迟获取相关集合时遇到了一些问题（OneToMany 关系）。

我有以下实体结构：

@Data
@Entity
@NoArgsConstructor
@AllArgsConstructor
@Builder(toBuilder = true)
public class Merchant implements Serializable {

  @Id private String name;

  private String displayName;

  private String staticSiteAddress;

  private String emailFromAddress;

  private String emailFromName;

  private String etmEmailFromAddress;

  private String etmEmailFromName;

  private String phone;

  private String username;

  @Embedded private PasswordHash password;

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @OneToMany(mappedBy = "merchant", fetch = FetchType.LAZY)
  @Builder.Default
  private Set<MerchantStore> stores = new HashSet<>();

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @OneToMany(mappedBy = "merchant", fetch = FetchType.LAZY)
  @Builder.Default
  private Set<CustomWebLink> customWebLinks = new HashSet<>();

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @OneToMany(mappedBy = "merchant", fetch = FetchType.LAZY)
  @Builder.Default
  private Set<LoyaltyPlan> loyaltyPlans = new HashSet<>();

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @OneToMany(mappedBy = "merchant", fetch = FetchType.LAZY)
  @Builder.Default
  private Set<MerchantPref> merchantPrefs = new HashSet<>();

}

在手头上，我可以使用以下存储库方法毫无问题地获取第一级相关实体（即merchantPrefs）：

@NonNull
@Override
@Cacheable("merchant")
@Join(value = "stores", type = Join.Type.LEFT_FETCH)
@Join(value = "customWebLinks", type = Join.Type.LEFT_FETCH)
@Join(value = "merchantPrefs", type = Join.Type.LEFT_FETCH)
@Join(value = "loyaltyPlans", type = Join.Type.LEFT_FETCH)
Optional<Merchant> findById(@NonNull @NotNull String s);

但是，当我尝试从该实体中获取最里面的集合时，例如 awards：

@Data
@Entity
public class LoyaltyPlan implements Serializable {

  @EmbeddedId private LoyaltyPlanID id;

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @ManyToOne(fetch = FetchType.LAZY)
  @MapsId("merchant")
  @JoinColumn(name = "merchant", nullable = false)
  private Merchant merchant;

  private String displayName;

  private String emailFromName;

  private String emailFromAddress;

  private String uniqueId;

  private boolean defaultPlan;

  private float pointsFactor;

  private boolean hasGiftCards;

  private boolean hasLoyaltyCards;

  private boolean usesName;

  private boolean hasEmail;

  private boolean hasCellPhone;

  private boolean needsGiftCards;

  private boolean needsLoyaltyCards;

  private boolean needsName;

  private boolean needsEmail;

  private boolean needsCellPhone;

  private int signupBonus;

  private int closingAwardThreshold;

  private int maxPointsPerOrder;

  private int minPricePerOrder;

  private int recentHistoryDays;

  private int expiringCouponReminderDays;

  @ToString.Exclude
  @EqualsAndHashCode.Exclude
  @OneToMany(mappedBy = "loyaltyPlan", fetch = FetchType.LAZY)
  private List<LoyaltyPlanAward> awards;
}

我收到了LazyInitializationException。

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: fts.marketing.entities.plan.LoyaltyPlan.awards, could not initialize proxy - no Session
    at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:606)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:218)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:387)
    at java.base/java.lang.Iterable.forEach(Iterable.java:74)
    at fts.marketing.TestController.doSomething(TestController.java:29)
    at fts.marketing.$TestControllerDefinition$Intercepted.$$access$$doSomething(Unknown Source)
    at fts.marketing.$TestControllerDefinition$$exec1.invokeInternal(Unknown Source)
    at io.micronaut.context.AbstractExecutableMethod.invoke(AbstractExecutableMethod.java:146)
    at io.micronaut.aop.chain.MethodInterceptorChain.proceed(MethodInterceptorChain.java:73)
    at io.micronaut.transaction.interceptor.TransactionalInterceptor.intercept(TransactionalInterceptor.java:134)
    at io.micronaut.aop.chain.MethodInterceptorChain.proceed(MethodInterceptorChain.java:82)
    at fts.marketing.$TestControllerDefinition$Intercepted.doSomething(Unknown Source)
    at fts.marketing.$TestControllerDefinition$$exec1.invokeInternal(Unknown Source)
    at io.micronaut.context.AbstractExecutableMethod.invoke(AbstractExecutableMethod.java:146)
    at io.micronaut.context.DefaultBeanContext$4.invoke(DefaultBeanContext.java:474)
    at io.micronaut.web.router.AbstractRouteMatch.execute(AbstractRouteMatch.java:312)
    at io.micronaut.web.router.RouteMatch.execute(RouteMatch.java:118)
    at io.micronaut.http.server.netty.RoutingInBoundHandler.lambda$buildResultEmitter$10(RoutingInBoundHandler.java:1369)
    at io.reactivex.internal.operators.flowable.FlowableDefer.subscribeActual(FlowableDefer.java:35)
    at io.reactivex.Flowable.subscribe(Flowable.java:14935)
    at io.reactivex.Flowable.subscribe(Flowable.java:14882)
    at io.micronaut.http.server.context.ServerRequestContextFilter.lambda$doFilter$0(ServerRequestContextFilter.java:62)
    at io.reactivex.internal.operators.flowable.FlowableFromPublisher.subscribeActual(FlowableFromPublisher.java:29)
    at io.reactivex.Flowable.subscribe(Flowable.java:14935)
    at io.reactivex.Flowable.subscribe(Flowable.java:14885)
    at io.micronaut.http.server.netty.RoutingInBoundHandler.lambda$buildExecutableRoute$6(RoutingInBoundHandler.java:1074)
    at io.micronaut.web.router.DefaultUriRouteMatch$1.execute(DefaultUriRouteMatch.java:80)
    at io.micronaut.web.router.RouteMatch.execute(RouteMatch.java:118)
    at io.micronaut.http.server.netty.RoutingInBoundHandler.handleRouteMatch(RoutingInBoundHandler.java:698)
    at io.micronaut.http.server.netty.RoutingInBoundHandler.channelRead0(RoutingInBoundHandler.java:554)
    at io.micronaut.http.server.netty.RoutingInBoundHandler.channelRead0(RoutingInBoundHandler.java:1

此外，这似乎是一个零星的问题，因为有时相同的代码似乎工作正常。我不太确定出了什么问题，我认为我已经正确地建模了这些关系，因为在迁移到 micronaut-data 之前这些关系都很好。

我不知道我在这里做错了什么，如果能提供任何帮助来解决这个问题，我将不胜感激。

【问题讨论】：

在这种情况下使用@Transactional
我确实使用它，但似乎无法解决问题。
可能你放错地方了。肯定与交易有关
我相当确定我在正确的位置有事务注释（即尝试获取数据的服务方法），所以不，我认为这不是背后的原因。
你使用缓存吗？

标签： java micronaut micronaut-data

【解决方案1】：

在 Micronaut 中，不存在 OpenSessionInView 的概念。当事务已经关闭时，您似乎正在尝试访问该关系。看这个：https://micronaut-projects.github.io/micronaut-sql/latest/guide/index.html#_understanding_lazyinitializationexception

解决方案：

不要使用懒惰。而是每次都使用存储库访问数据库你需要这份清单。
使用 EAGER。
在进行查询的方法中使用@Transactional。

【讨论】：