Jpa Stackoverflow exception in ManyToOne relation

I have sections inside which I can have subsections and inside them I can have deeper level of sections and further. Entity:

@Data
@Table(name = "section")
@Entity
@NoArgsConstructor
public class Section {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column
  private Long id;

  @Column private String title;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "parent_id")
  private Section parent;

  @JsonIgnore
  @OneToMany(fetch = FetchType.EAGER, mappedBy = "parent")
  private Set<Section> children;

  public Section(Long id, String title, Section parent) {
    this.id = id;
    this.title = title;
    this.parent = parent;
  }
}

I save all data in h2 database for testing purposes. Repository class:

@Repository
public interface SectionRepository extends JpaRepository<Section, Long> {
  List<Section> findAllByParentId(Long parentId);
}

What I have in h2:

enter image description here

I want to find only these sections which doesn’t have parent(First two which have null in parent_id column). How I’m trying to do it:

Section about = new Section(null, "about", null);
Section production = new Section(null, "production", null);

sectionRepository.save(about);
sectionRepository.save(production);

Section subsectionOne = new Section(null, "subsectionOne", production); // without adding
Section subsectionTwo = new Section(null, "subsectionTwo", production); // these two subsections
                                 sectionRepository.save(subsectionOne); // and saving them to db
                                 sectionRepository.save(subsectionTwo); // I don't receive any error on findAllByParentId(null) method call

sectionRepository.findAllByParentId(null); // action
java.lang.StackOverflowError: null
    at org.h2.util.ParserUtil.getSaveTokenType(ParserUtil.java:592) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.read(Parser.java:5092) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readIf(Parser.java:5011) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readTerm(Parser.java:4306) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readFactor(Parser.java:3343) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readSum(Parser.java:3330) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readConcat(Parser.java:3305) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readCondition(Parser.java:3108) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.readExpression(Parser.java:3059) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parseSelectExpressions(Parser.java:2931) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parseSelect(Parser.java:2952) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parseQuerySub(Parser.java:2817) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parseSelectUnion(Parser.java:2649) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parseQuery(Parser.java:2620) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parsePrepared(Parser.java:868) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parse(Parser.java:843) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.parse(Parser.java:815) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.command.Parser.prepareCommand(Parser.java:738) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.engine.Session.prepareLocal(Session.java:657) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.engine.Session.prepareCommand(Session.java:595) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.jdbc.JdbcConnection.prepareCommand(JdbcConnection.java:1235) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.jdbc.JdbcPreparedStatement.<init>(JdbcPreparedStatement.java:76) ~[h2-1.4.200.jar:1.4.200]
    at org.h2.jdbc.JdbcConnection.prepareStatement(JdbcConnection.java:352) ~[h2-1.4.200.jar:1.4.200]
    at com.zaxxer.hikari.pool.ProxyConnection.prepareStatement(ProxyConnection.java:337) ~[HikariCP-3.4.5.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyConnection.prepareStatement(HikariProxyConnection.java) ~[HikariCP-3.4.5.jar:na]
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$5.doPrepare(StatementPreparerImpl.java:149) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl$StatementPreparationTemplate.prepareStatement(StatementPreparerImpl.java:176) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.jdbc.internal.StatementPreparerImpl.prepareQueryStatement(StatementPreparerImpl.java:151) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.prepareQueryStatement(AbstractLoadPlanBasedLoader.java:198) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:162) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:104) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:260) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]
    at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:352) ~[na:na]
    at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:260) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:102) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.25.Final.jar:5.4.25.Final]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at lv.sawex.core.sections.Section.hashCode(Section.java:10) ~[classes/:na]
    at java.base/java.util.HashMap.hash(HashMap.java:339) ~[na:na]
    at java.base/java.util.HashMap.put(HashMap.java:607) ~[na:na]
    at java.base/java.util.HashSet.add(HashSet.java:220) ~[na:na]

spring.jpa.show-sql=true Sql result: last sql query recursively repeats.

Hibernate: select section0_.id as id1_1_, section0_.parent_id as parent_i4_1_, section0_.title as title2_1_, section0_.titlelv as titlelv3_1_ from section section0_ left outer join section section1_ on section0_.parent_id=section1_.id where section1_.id is null
Hibernate: select children0_.parent_id as parent_i4_1_0_, children0_.id as id1_1_0_, children0_.id as id1_1_1_, children0_.parent_id as parent_i4_1_1_, children0_.title as title2_1_1_, children0_.titlelv as titlelv3_1_1_ from section children0_ where children0_.parent_id=?
Hibernate: select children0_.parent_id as parent_i4_1_0_, children0_.id as id1_1_0_, children0_.id as id1_1_1_, children0_.parent_id as parent_i4_1_1_, children0_.title as title2_1_1_, children0_.titlelv as titlelv3_1_1_ from section children0_ where children0_.parent_id=?

Where is the problem?

Answer

Judging by the stack trace and Lombok annotations used, the problem may be related to recursive invocation of hashCode(). Lombok’s @Data will generate implementations for equals and hashCode methods, and by default these implementations will use all declared fields, including both parent and children in your case. This means that trying to calculate hash code for “production” entry will trigger calculations for “subsectionOne”/”subsectionTwo”, leading back to “production” via parent property.

Excluding the set from hashCode implementation via adding @EqualsAndHashCode.Exclude to the children field should solve the issue

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