Hibernate @ManyToMany persist-CodePudding

I have a problem with @ManyToMany relationShip.

I have an Entity Category that in DB have predefined inserts.

And I have Entity Trigger, that must contain predefined Category :

@Entity
@Data
public class Category {

    @Id
    private Long id;

    private String name;

    @ManyToMany(cascade = CascadeType.ALL, mappedBy = "categories")
    private Set<Trigger> trigger;

@Entity
@Data
public class Trigger {

    @ManyToMany()
    private Set<Category> categories;
}



Trigger trigger = new Trigger();
trigger.setName(triggerDTO.getName());
trigger.setCategories(triggerDTO.getCategories()
            .stream()
            .map(c -> categoryRepository.findByName(c.getName()))
            .collect(Collectors.toSet()));

So when I persist the first Trigger everything is fine, but when I try to persist next Trigger, I see:

java.lang.StackOverflowError: null
  at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:401) ~[postgresql-42.2.23.jar:42.2.23]
  at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:164) ~[postgresql-42.2.23.jar:42.2.23]
  at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:114) ~[postgresql-42.2.23.jar:42.2.23]
  at com.zaxxer.hikari.pool.ProxyPreparedStatement.executeQuery(ProxyPreparedStatement.java:52) ~[HikariCP-4.0.3.jar:na]
  at com.zaxxer.hikari.pool.HikariProxyPreparedStatement.executeQuery(HikariProxyPreparedStatement.java) ~[HikariCP-4.0.3.jar:na]
  at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:57) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.getResultSet(AbstractLoadPlanBasedLoader.java:390) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:104) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at com.myapp.domain.trigger.Trigger.hashCode(Trigger.java:13) ~[classes/:na]
  at java.base/java.util.HashMap.hash(HashMap.java:340) ~[na:na]
  at java.base/java.util.HashMap.put(HashMap.java:612) ~[na:na]
  at java.base/java.util.HashSet.add(HashSet.java:221) ~[na:na]
  at java.base/java.util.AbstractCollection.addAll(AbstractCollection.java:336) ~[na:na]
  at org.hibernate.collection.internal.PersistentSet.endRead(PersistentSet.java:355) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollection(CollectionLoadContext.java:239) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:224) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.engine.loading.internal.CollectionLoadContext.endLoadingCollections(CollectionLoadContext.java:198) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.process.internal.CollectionReferenceInitializerImpl.endLoading(CollectionReferenceInitializerImpl.java:154) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishLoadingCollections(AbstractRowReader.java:253) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.process.internal.AbstractRowReader.finishUp(AbstractRowReader.java:211) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.process.internal.ResultSetProcessorImpl.extractResults(ResultSetProcessorImpl.java:96) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:105) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:87) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:710) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:76) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.event.service.internal.EventListenerGroupImpl.fireEventOnEachListener(EventListenerGroupImpl.java:99) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:2163) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:589) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:264) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:585) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:149) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at org.hibernate.collection.internal.PersistentSet.hashCode(PersistentSet.java:458) ~[hibernate-core-5.4.32.Final.jar:5.4.32.Final]
  at com.myapp.domain.trigger.observation.component.Category.hashCode(Category.java:10) ~[classes/:na]
  at java.base/java.util.HashMap.hash(HashMap.java:340) ~[na:na]
  at java.base/java.util.HashMap.put(HashMap.java:612) ~[na:na]
  at java.base/java.util.HashSet.add(HashSet.java:221) ~[na:na]

If change Set to List, work correct, why?

CodePudding user response：

Concisely: Using

@NoArgsConstructor
@Getter

is enough for serializing/deserializing instead of your current @Data

The reason it doesn't work for Set is @EqualsAndHashCode in your @Data.

Here, every time you insert a Trigger, the JPA firstly gets your Trigger and its dependencies Categorys. For example, you have 1 Trigger with 1 Category

select
    trigger0_.id as id1_1_0_ 
from
    trigger trigger0_ 
where
    trigger0_.id=?

select
    category0_.id as id1_0_0_,
    category0_.name as name2_0_0_ 
from
    category category0_ 
where
    category0_.id=?

And because you put your Set<Trigger> in a Category class, so this Trigger's hashcode will be calculated using the Lombok @EqualsAndHashCode.That's why JPA need to load this Trigger in order to calculate the hashcode then

select
    trigger0_.categories_id as categori2_2_0_,
    trigger0_.trigger_id as trigger_1_2_0_,
    trigger1_.id as id1_1_1_ 
from
    trigger_categories trigger0_ 
inner join
    trigger trigger1_ 
        on trigger0_.trigger_id=trigger1_.id 
where
    trigger0_.categories_id=?

So at the first time you insert, there is no Trigger, it can easily calculate the hashcode for the Category and thing's done here

insert into trigger(id) values (?)
insert into trigger_categories(trigger_id, categories_id) values (?, ?)

But at the second time, if you insert a new Trigger with the previous Category, this time the previous Category linked to the previous Trigger, so when hashCode is calculated, a loop will happen

select
    trigger0_.categories_id as categori2_2_0_,
    trigger0_.trigger_id as trigger_1_2_0_,
    trigger1_.id as id1_1_1_ 
from
    trigger_categories trigger0_ 
inner join
    trigger trigger1_ 
        on trigger0_.trigger_id=trigger1_.id 
where
    trigger0_.categories_id=?

select
    categories0_.trigger_id as trigger_1_2_0_,
    categories0_.categories_id as categori2_2_0_,
    category1_.id as id1_0_1_,
    category1_.name as name2_0_1_ 
from
    trigger_categories categories0_ 
inner join
    category category1_ 
        on categories0_.categories_id=category1_.id 
where
    categories0_.trigger_id=?

If you want to keep @EqualsAndHashCode, try to ignore relational fields, for example

@NoArgsConstructor
@Getter
@EqualsAndHashCode(of = {"id"})

Or turn it into List as you said.