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ConcurrentModificationException in query execution [message #1832426]

Thu, 17 September 2020 15:48

Michael Earl

Messages: 3
Registered: September 2020

Junior Member

We upgraded from Java 8 to Java 11 and from EclipseLink 2.2.0 to 2.7.7 and now we are getting ConcurrentModificationException on some of our queries. Our code has not changed with the Java and EclipseLink library upgrades. Also, this is not an issue with sharing EntityManager's between threads as I single threaded all queries and I still get the same issues. Also, this does not occur on all entity queries but seems to be isolated to a few Entities with OneToMany and ManyToOne relationships. Also, when the OneToMany side of the releationship is removed from the problematic Entities, the problem for that Entities goes away. For instance I removed the following OneToMany relationship to SiteHost: but kept the ManyToOne side of the relationship.

@Entity
@Table( name = "TOUCHSCREEN_TYPE" )
public class TouchscreenType extends AbstractDataModel<TouchscreenType> implements Serializable
{
private static final long serialVersionUID = 1L;
@Id
@Column( name = "TOUCHSCREEN_TYPE_ID" )
private int touchscreenTypeId;
@Column( name = "MANUFACTURER_NAME" )
private String manufacturerName;
@Column( name = "MOUSE_ACTION_TYPE" )
private String mouseActionType;
//bi-directional many-to-one association to ipAddress
@OneToMany( mappedBy = "touchscreenType" )
private Set<SiteHost> siteHosts;

-- other side of the relationship
// bi-directional many-to-one association to TouchscreenType
@ManyToOne
@JoinColumn( name = "TOUCHSCREEN_TYPE_ID" )
private TouchscreenType touchscreenType;

----------------------Exception--------------------------
java.util.ConcurrentModificationException: null
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1493) ~[?:?]
at java.util.HashMap$KeyIterator.next(HashMap.java:1516) ~[?:?]
at org.eclipse.persistence.indirection.IndirectSet$1.next(IndirectSet.java:523) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.queries.InterfaceContainerPolicy.next(InterfaceContainerPolicy.java:303) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.queries.ContainerPolicy.next(ContainerPolicy.java:1180) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:369) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:371) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:371) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:373) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:371) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:373) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:371) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.CollectionMapping.buildExpression(CollectionMapping.java:371) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.mappings.ObjectReferenceMapping.buildExpression(ObjectReferenceMapping.java:194) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildExpressionFromExample(ObjectBuilder.java:659) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.queries.QueryByExampleMechanism.buildSelectionCriteria(QueryByExampleMechanism.java:80) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.DatabaseQuery.buildSelectionCriteria(DatabaseQuery.java:544) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ObjectLevelReadQuery.prePrepare(ObjectLevelReadQuery.java:2152) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ObjectLevelReadQuery.checkPrePrepare(ObjectLevelReadQuery.java:985) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ObjectLevelReadQuery.checkEarlyReturn(ObjectLevelReadQuery.java:910) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.DatabaseQuery.execute(DatabaseQuery.java:848) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute(ObjectLevelReadQuery.java:1191) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ReadAllQuery.execute(ReadAllQuery.java:485) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork(ObjectLevelReadQuery.java:1279) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery(UnitOfWorkImpl.java:2983) ~[eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1898) [eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1880) [eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery(AbstractSession.java:1845) [eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery(QueryImpl.java:262) [eclipselink.jar:2.7.7.v20200504-69f2c2b80d]
at org.eclipse.persistence.internal.jpa.QueryImpl.getResultList(QueryImpl.java:482) [eclipselink.jar:2.7.7.v20200504-69f2c2b80d]

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Re: ConcurrentModificationException in query execution [message #1832471 is a reply to message #1832426]

Fri, 18 September 2020 13:26

Michael Earl

Messages: 3
Registered: September 2020

Junior Member

Additional information. We are using the following query hints:

query.setHint( QueryHints.REFRESH, HintValues.TRUE );
query.setHint( QueryHints.REFRESH_CASCADE, CascadePolicy.CascadeAllParts );

I tried EclipseLink 2.7.8 and 3.0.0 and the issue persists.

[Updated on: Fri, 18 September 2020 13:28]

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Re: ConcurrentModificationException in query execution [message #1832609 is a reply to message #1832471]

Mon, 21 September 2020 20:17

Chris Delahunt

Messages: 1389
Registered: July 2009

Senior Member

That is a lot of changes from when it was 'working' to now. Key in the stack though is that it has ObjectBuilder.buildExpressionFromExample, indicating this is a query by example query. As you are getting a concurrent modification exception on IndirectSet, I would guess you are passing something into the query that is shared, and so not thread safe for concurrent access.

Check your application that you are not passing something from the shared cache to your query (a read-only instance perhaps) when some other processes might have changes being merged into it.

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Re: ConcurrentModificationException in query execution [message #1832648 is a reply to message #1832609]

Tue, 22 September 2020 15:20

Michael Earl

Messages: 3
Registered: September 2020

Junior Member

Thanks for the response Chris. You are correct, we are using QBE and the query is being performed by the JPA entity. I'll have to think about your advice. I

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