Micronaut data problem lazily fetching related entities

Question

I am currently in the process of incorporating micronaut data into an existing micronaut project (as part of upgrading it) and I am experiencing some problems regarding lazily fetching related collections (with a OneToMany relation).

I have the following entity structure:

@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<>();

}

With in on hand I am able to fetch the first level related entities fine (ie merchantPrefs ) with no issue using the following repository method:

@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);

However when I try to fetch an innermost collection for example awards from this entity:

@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;
}

I get a 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

Furthemore this seems to be a sporadic issue, as sometimes the same code seems to be working OK. I am not really sure what is wrong and I think I have modelled the relations correctly as those have been fine before migrating to micronaut-data .

I do not know what I am doing wrong here and any help would highly appreciated in order to resolve this.

Answer 1

In Micronaut the concept of OpenSessionInView doesn't exist. It seems that you are trying to access to the relation when the transaction is already closed. Look at this: https://micronaut-projects.github.io/micronaut-sql/latest/guide/index.html#_understanding_lazyinitializationexception

Solutions:

1. Don't use Lazy. Instead go to the DB with a repository every time you need the list.
2. Use EAGER.
3. Use @Transactional in the method that make the query.