Spring Data JPA - "could not initialize proxy - no Session" - With Methods marked as transactional

I have a model that has a pretty large graph of sub entities and hibernate ends up making around 9 statements to lazily fetch all of the data needed but about 4 levels deep I get a "could not initialize proxy - no Session" error and I am not sure why.

Controller

@Transactional(readOnly = true)
@RequestMapping(value = "/v2/plans", method = RequestMethod.GET)
public @ResponseBody List<PlanPresenter> show(HttpServletRequest request) throws Exception {
  List<PlanPresenter> planPresenters = new ArrayList<>();

  CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
  CriteriaQuery<Plan> planQuery = criteriaBuilder.createQuery(Plan.class);
  Root<Plan> root = planQuery.from(Plan.class);

  if (request.getParameter("region") != null || request.getParameter("group") != null) {
    List<Predicate> criteria = new ArrayList<Predicate>();
	if (request.getParameter("region") != null) {
	  criteria.add(criteriaBuilder.equal(root.get(Plan_.region), request.getParameter("region")));
	}
	
	if (request.getParameter("group") != null) {
	  criteria.add(criteriaBuilder.equal(root.get(Plan_.groupCode), request.getParameter("group")));
	  criteria.add(root.get(Plan_.planSetId).in(groupPlanSetIds));
	} else {
	  criteria.add(root.get(Plan_.planSetId).in(currentPlanSetIds));
	}

    Query query = entityManager.createQuery(planQuery.where(criteriaBuilder.and(criteria.toArray(new Predicate[]{}))));
  
    for (Plan plan : (List<Plan>)query.getResultList()) {
      planPresenters.add(new PlanPresenter(plan));
    }
  }

  return planPresenters;
}

Presenter

public class PlanPresenter {
  public String id;
  public String plan_set_id;
  public String region;
  public String name;
  public String description;
  public HashMap<String, Object> details = new HashMap<String, Object>();

  public PlanPresenter(Plan plan) throws Exception {
    this.id = String.valueOf(plan.id);
    this.plan_set_id = String.valueOf(plan.planSetId);
    this.region = plan.region.trim();
    this.name = plan.getName();
    this.description = plan.getDescription();

    this.details.put("spanish_plan", plan.isSpanishPlan());
    this.details.put("mutually_exclusive", plan.isMutuallyExclusive());
    this.details.put("group_plan", plan.isGroupPlan());
    this.details.put("group_code", plan.groupCode.trim());
    this.details.put("family_plan", plan.isFamilyPlan());
    this.details.put("price", plan.getPrice());
    this.details.put("enrollment_fee", plan.getEnrollmentFee());
    this.details.put("riders", plan.getRiders());
  }
}

Plan

@Entity
public class Plan implements Serializable {
  private static final long serialVersionUID = 7639611964474770505L;

  private static List<String> familyPlanShortNames = Arrays.asList("ABCD");
  @Transient
  private String description = "";

  (Column definitions)

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "XXXX", insertable = false, updatable = false, nullable = true)
  @NotFound(action = NotFoundAction.IGNORE)
  public PlanDetail planDetail;

  @OneToMany(fetch = FetchType.LAZY)
  @JoinColumn(name = "XXXX", insertable = false, updatable = false, nullable = true)
  @OrderBy("XXXX")
  @NotFound(action = NotFoundAction.IGNORE)
  public List<Rider> riders;

  public String getName() {
    return this.planDetail != null ? this.planDetail.longName.trim() : null;
  }

  public Boolean isSpanishPlan() {
    return this.language.trim().equals("ES");
  }

  public Boolean isMutuallyExclusive() {
    return this.mutuallyExclusive.trim().equals("Y");
  }

  public Boolean isGroupPlan() {
    return this.groupCode != null && !this.groupCode.trim().equals("");
  }

  public Boolean isFamilyPlan() {
    return familyPlanShortNames.contains(this.planDetail.shortName.trim());
  }

  public BigDecimal getPrice() {
    return this.planDetail != null ? this.planDetail.price.setScale(2) : null;
  }

  public BigDecimal getEnrollmentFee() {
    return this.planDetail != null ? this.planDetail.enrollmentFee.setScale(2) : null;
  }

  public String getDescription() {
    if (this.planDetail != null && this.planDetail.brochureSections != null) {
      this.planDetail.brochureSections.forEach((brochureSection) -> {
        if (brochureSection.type.trim().equals("P1") && brochureSection.order == 1) {
          this.description = this.description + " " + brochureSection.text.trim();
        }
      });
    }

    return this.description.trim();
  }

  public List<HashMap<String, Object>> getRiders() {
    List<HashMap<String, Object>> riders = new ArrayList<HashMap<String, Object>>();
    if (this.riders != null && this.riders.size() > 0) {
      this.riders.forEach((rider) -> {
        HashMap<String, Object> planRider = new HashMap<String, Object>();
        planRider.put("name", rider.getName());
        planRider.put("price", rider.getPrice());
        planRider.put("description", rider.getDescription());
        riders.add(planRider);
      });
    }
    return riders;
  }
}

Plan Detail

@Entity
public class PlanDetail implements Serializable {
  private static final long serialVersionUID = 2256881691562712018L;

  (Column definitions)

  @OneToMany(fetch = FetchType.LAZY)
  @JoinColumn(name = "XXXX", referencedColumnName = "XXXX", insertable = false, updatable = false, nullable = true)
  @OrderBy("XXXX")
  @NotFound(action = NotFoundAction.IGNORE)
  public List<BrochureSection> brochureSections;
}

Brochure Section

@Entity
public class BrochureSection implements Serializable {
  private static final long serialVersionUID = 1856191232387921427L;

  (Column definitions)
}

Exception

org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.models.PlanDetail.brochureSections, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:576) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:215) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:555) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:143) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:294) ~[hibernate-core-4.3.11.Final.jar:4.3.11.Final]
at java.lang.Iterable.forEach(Iterable.java:74) ~[?:1.8.0_66]
at com.models.Plan.getDescription(Plan.java:100) ~[classes/:?]
at com.presenters.v2.PlanPresenter.<init>(PlanPresenter.java:20) ~[classes/:?]
at com.controllers.v2.PlansController.show(PlansController.java:64) ~[classes/:?]

Any help would be appreciated.

If you would like to keep Lazy Load and you are using Spring Boot, just add the config below in your application.properties:

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true

The lazy loading can be kept, without the setting the enable_lazy_load_no_trans parameter. The simplest solution I found was @NamedEntityGraph while using Spring Data JPA. https://www.baeldung.com/spring-data-jpa-named-entity-graphs

The downside was I could not have more than one collection in the @NamedEntityGraph. Adding a second collection resulted in an exception org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags:

Therefore, if you don't want to use the anti-pattern, and only have one collection you are trying to load, the @NamedEntityGraph and @EntityGrpah works with Spring Data JPA.

I had the same exception and the issue was, I had an entity where the mapping was missed

@Entity
Class A {
}

@Entity
Class B {

   private A a;
}

Solution

@Entity
Class B {

  @OneToOne
  @MapsId
  private A a;
}

spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true it is an anti-pattern and highly recommend to avoid to use it.

could not initialize proxy exception will occur often when child class contains @JsonIgnoreProperties({"hibernateLazyInitializer", "handler"}) in your relationship.

I recommend to use fetch = FetchType.EAGER in your relationship instead of using LAZY. It is not the best way but it is far better than using anti-pattern.