NullPointerException during cascading saves of bidirectional domain objects

[joemccall86]

Reproducible example: https://github.com/joemccall86/grails-bidirectional-cascade-test (includes working 2.4.5 project and non-working 3.0.8 project).

This is behavior that worked in Grails 2.4.5, but seems broken in Grails 3.0.x. Given a domain class Team that hasMany = [players: Player], and each player hasOne = [contract: Contract], and the bi-directional associations are setup properly, a save(flush: true) on a Team object should cascade saves down to Player and Contract. What happens instead is a NullPointerException.

This seems very similar to #698. Running JDK 8 on Windows 10.

Here is the stacktrace:

java.lang.NullPointerException
    at org.hibernate.engine.spi.BatchFetchQueue.removeBatchLoadableEntityKey(BatchFetchQueue.java:163)
    at org.hibernate.engine.internal.StatefulPersistenceContext.addEntity(StatefulPersistenceContext.java:389)
    at org.hibernate.engine.internal.StatefulPersistenceContext.addEntity(StatefulPersistenceContext.java:462)
    at org.hibernate.action.internal.AbstractEntityInsertAction.makeEntityManaged(AbstractEntityInsertAction.java:143)
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:203)
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:181)
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:216)
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:334)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:289)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:114)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.grails.orm.hibernate.support.ClosureEventTriggeringInterceptor.onSaveOrUpdate(ClosureEventTriggeringInterceptor.java:113)
    at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:684)
    at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:676)
    at org.hibernate.engine.spi.CascadingActions$5.cascade(CascadingActions.java:235)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:350)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:293)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161)
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:118)
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:470)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:295)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:114)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.grails.orm.hibernate.support.ClosureEventTriggeringInterceptor.onSaveOrUpdate(ClosureEventTriggeringInterceptor.java:113)
    at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:684)
    at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:676)
    at org.hibernate.engine.spi.CascadingActions$5.cascade(CascadingActions.java:235)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:350)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:293)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161)
    at org.hibernate.engine.internal.Cascade.cascadeCollectionElements(Cascade.java:379)
    at org.hibernate.engine.internal.Cascade.cascadeCollection(Cascade.java:319)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:296)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:161)
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:118)
    at org.hibernate.event.internal.AbstractSaveEventListener.cascadeAfterSave(AbstractSaveEventListener.java:470)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:295)
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:195)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:126)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:209)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:194)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:114)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.grails.orm.hibernate.support.ClosureEventTriggeringInterceptor.onSaveOrUpdate(ClosureEventTriggeringInterceptor.java:113)
    at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:684)
    at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:676)
    at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:671)
    at org.grails.orm.hibernate.AbstractHibernateGormInstanceApi.performSave_closure3(AbstractHibernateGormInstanceApi.groovy:255)
    at groovy.lang.Closure.call(Closure.java:426)
    at org.grails.orm.hibernate.GrailsHibernateTemplate.doExecute(GrailsHibernateTemplate.java:198)
    at org.grails.orm.hibernate.GrailsHibernateTemplate.execute(GrailsHibernateTemplate.java:142)
    at org.grails.orm.hibernate.GrailsHibernateTemplate.execute(GrailsHibernateTemplate.java:112)
    at org.grails.orm.hibernate.AbstractHibernateGormInstanceApi.performSave(AbstractHibernateGormInstanceApi.groovy:254)
    at org.grails.orm.hibernate.AbstractHibernateGormInstanceApi.save(AbstractHibernateGormInstanceApi.groovy:179)
    at org.grails.datastore.gorm.GormEntity$Trait$Helper.save(GormEntity.groovy:165)
    at baseball.test.BiDirectionalAssociationSpecSpec.$tt__setupData(BiDirectionalAssociationSpecSpec.groovy:42)
    at baseball.test.BiDirectionalAssociationSpecSpec.setupData_closure1(BiDirectionalAssociationSpecSpec.groovy)
    at groovy.lang.Closure.call(Closure.java:426)
    at groovy.lang.Closure.call(Closure.java:442)
    at grails.transaction.GrailsTransactionTemplate$1.doInTransaction(GrailsTransactionTemplate.groovy:67)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:133)
    at grails.transaction.GrailsTransactionTemplate.executeAndRollback(GrailsTransactionTemplate.groovy:64)
    at baseball.test.BiDirectionalAssociationSpecSpec.$tt__$spock_feature_0_0(BiDirectionalAssociationSpecSpec.groovy:20)
    at baseball.test.BiDirectionalAssociationSpecSpec.a valid team is bootstrapped into the test_closure2(BiDirectionalAssociationSpecSpec.groovy)
    at groovy.lang.Closure.call(Closure.java:426)
    at groovy.lang.Closure.call(Closure.java:442)
    at grails.transaction.GrailsTransactionTemplate$1.doInTransaction(GrailsTransactionTemplate.groovy:67)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:133)
    at grails.transaction.GrailsTransactionTemplate.executeAndRollback(GrailsTransactionTemplate.groovy:64)
    at baseball.test.BiDirectionalAssociationSpecSpec.a valid team is bootstrapped into the test(BiDirectionalAssociationSpecSpec

[jd73]

I am experiencing the same issue with grails 3.0.7

[denis111]

It happens in 2.5.1 also if there's beforeSave method in the domain class.

a quick workaround in BootStrap.groovy would be:

def oldRemoveBatchLoadableEntityKey = BatchFetchQueue.metaClass.&removeBatchLoadableEntityKey

        BatchFetchQueue.metaClass.removeBatchLoadableEntityKey = { EntityKey key ->
            return key ? oldRemoveBatchLoadableEntityKey.invoke(key) : null
        }

[graemerocher]

The issue is that the player property is unassigned when save() is called:

The following corrects the problem:

    def c = new Contract(
            expiration: new Date(),
            salary: 40_000_000
    )
    def p = new Player(
            firstName: "John",
            lastName: "Doe",
            position: "Pitcher",
            contract: c
    )
    c.player = p
    padres.addToPlayers(p)

Probably earlier versions of Grails aligned these associations before saving, I'll try track down the change, but it is not as serious as I thought and the above is a workaround

[joemccall86]

Thanks for taking a look at it. I'd like to help any way I could if you could point me in the right direction. A lot of our code was written based on those cascading behaviors, and my time would likely be better spent contributing a patch than adding this workaround everywhere we save an object.

[graemerocher]

I believe the problem is that in the latest versions of the Hibernate plugin this method is no longer present:

https://github.com/grails/grails-data-mapping/blob/3.x/grails-datastore-gorm-hibernate4/src/main/groovy/org/codehaus/groovy/grails/orm/hibernate/metaclass/AbstractSavePersistentMethod.java#L246

This is because the logic for save() was replaced / moved to:

https://github.com/grails/grails-data-mapping/blob/4.x/grails-datastore-gorm/src/main/groovy/org/grails/datastore/gorm/GormInstanceApi.groovy#L169

But obviously some behaviour seems to have not been retained. Since this is a Hibernate specific problem, it would probably make sense to override and provide an impl in the child class:

https://github.com/grails/grails-data-mapping/blob/4.x/grails-datastore-gorm-hibernate4/src/main/groovy/org/grails/orm/hibernate/HibernateGormInstanceApi.groovy

Thanks for the willingness to contribute.

[joemccall86]

Wow, it turns out I am in completely over my head on this one :-).

Basically I started out trying to make the sample application into a unit test on the grails-datastore-gorm-hibernate4 module, based on BidirectionalOneToOneBelongsToCascadeSpec.groovy, making it pass in the 3.x branch (the plugin version in grails 2.x), and seeing if it fails on the 4.x branch (the plugin used in grails 3.x). I couldn't even set up a passing test for the 3.x branch. The integration test with team->player->contract passes, but as soon as I replicate that in the unit test I get the same NPE failure as above (also that workaround makes it pass).

In other words, I can't seem to wrap my head around why Grails 2.x even works in this case. All I can contribute is this discovery: this bug doesn't only happen with hasMany. It can be reproduced with nested hasOne/belongsTo associations.

class Foo {
    static hasOne = [bar: Bar]
}

class Bar {
    static belongsTo = [foo: Foo]
    static hasOne = [baz: Baz]
}

class Baz {
    static belongsTo = [bar: Bar]
}

new Foo(
    bar: new Bar(
        baz: new Baz()
    )
).save(flush: true)

When I run the above code:

Project	Test Type	Runs
Grails 2.4.5	Integration	YES, all three rows inserted
Grails 3.0.8	Integration	NO, NullPointerException above
grails-data-mapping 3.x branch	Unit	NO, NullPointerException above
grails-data-mapping 4.x branch	Unit	NO, NullPointerException above

One more thing: based on observations, foo.bar.foo == foo, but foo.bar.baz.bar == null, not foo.bar. Thus, this issue only seems to turn up when there is a chain of associations involved.

I hope this helps in some small way. I need to move onto another task, but feel free to ask me anything about the tests I wrote, or any other questions.