I am migrating from hibernate 3.5 to 5.0.3.FINAL. I am getting following error after migrated to 5. It's worked perfectly with 3.5. I am not sure what's causing this problem. "org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property".

Here is my entity classes.

Parent Entity:

@Entity
@Table(name = RmbModelConstants.PRC_IMPORT_JOBS)
public class ImportJob extends ComponentHistory {

public static final String SEQ_GENERATOR_NAME = "importJobsSeq";
public static final String SEQ_DB_NAME = "SEQ_PIJ";

@Id
@Column(name = EntityConstants.ID)
@SequenceGenerator(name = SEQ_GENERATOR_NAME, sequenceName = SEQ_DB_NAME)
@GeneratedValue(strategy = GenerationType.AUTO, generator = SEQ_GENERATOR_NAME)
private Long id;

@OneToOne(cascade = {CascadeType.ALL}, mappedBy = "importJob", fetch = FetchType.LAZY)
private ImportData importData;

Child Entity:

@Entity
@Table(name = RmbModelConstants.PRC_IMPORT_DATA)

public class ImportData {

public static final String SEQ_GENERATOR_NAME = "importDataSeq";
public static final String SEQ_DB_NAME = "SEQ_FSID";

@Id
@Column(name="JOB_ID")
@GeneratedValue(generator="gen")
@GenericGenerator(name="gen", strategy="foreign", parameters=@Parameter(name="property", value="importJob"))
private Long jobId;

@OneToOne
@PrimaryKeyJoinColumn
private ImportJob importJob;

Service Layer:

private ImportJob persistImportJob(Long libraryFeeScheduleId, String fileName, User user) {
ImportJob importJob = createImportJob(fileName, user);
ImportData importData = createImportData(importJob, fileStream);
importData .setImportJob(importJob);
importJob.setImportData(importData);

ImportJob createdImportJob = importJobJpaRepo.create(importJob);
}

public ImportData createImportData(ImportJob importJob, InputStream fileStream) {
ImportData importData = new ImportData();
importData.setFileName(importJob.getFileName());
importJob.setImportData(importData);
importData.setImportJob(importJob);
return importData;
}

protected static ImportJob createImportJob(String fileName, User user) {
ImportJob importJob = new ImportJob(user.getUserId());
importJob.setFileUploadedDate(DateUtils.getLocalDateTime());
importJob.setStatus(JobStatus.UPLOADED);
importJob.setFileName(fileName);
return importJob;
}

Jpa Layer:

public ImportJob create(ImportJob importJob){
return getEntityManager().merge(importJob);
}

Error:
2015-11-19T11:09:14,938 TRACE hibernate.resource.jdbc.internal.ResourceRegistryStandardImpl.releaseResources:286 - Releasing JDBC resources
2015-11-19T11:09:14,938 TRACE hibernate.resource.jdbc.internal.LogicalConnectionManagedImpl.close:220 - Logical connection closed
2015-11-19T11:09:14,938 ERROR rest.library.feeschedule.importjob.LibraryFeeScheduleImportRepresentationServiceImpl.upload:183 - Failed due to following exception javax.persistence.PersistenceException: org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property [com.mckesson.rem.domain.model.impl.ImportData.importJob]
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1692) ~[hibernate-entitymanager-5.0.1.Final.jar:5.0.1.Final]
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1602) ~[hibernate-entitymanager-5.0.1.Final.jar:5.0.1.Final]
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1608) ~[hibernate-entitymanager-5.0.1.Final.jar:5.0.1.Final]
at org.hibernate.jpa.spi.AbstractEntityManagerImpl.merge(AbstractEntityManagerImpl.java:1171) ~[hibernate-entitymanager-5.0.1.Final.jar:5.0.1.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_65]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_65]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_65]
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_65]
at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:241) ~[spring-orm-3.2.13.RELEASE.jar:3.2.13.RELEASE]
at com.sun.proxy.$Proxy75.merge(Unknown Source) ~[?:?]
at com.mckesson.rem.platform.repository.impl.GenericJpaRepository.makePersist(GenericJpaRepository.java:176) ~[common-3.1.0-SNAPSHOT.jar:?]
at com.mckesson.rem.domain.service.impl.ImportJobSrvcImpl.create(ImportJobSrvcImpl.java:63) ~[model-3.1.0-SNAPSHOT.jar:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_65]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_65]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_65]
at java.lang.reflect.Method.invoke(Method.java:497) ~[?:1.8.0_65]

try to set hibernate.id.new_generator_mappings=false;

if the issue persists even with this conf can you please open a thicket on JIRA https://hibernate.atlassian.net?

Thanks