@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@Table(uniqueConstraints = {@UniqueConstraint(columnNames = {"username"})})
public class User implements UserDetails
{
   @Id
   @GeneratedValue(strategy=GenerationType.AUTO)
   @Column(name = "user_id")
   private Long id;
...

@Entity
public class Performer extends User
{
   @Column(length = 32)
   private String phone;
   
   @OneToOne(cascade = CascadeType.ALL, mappedBy = "performer")
   private Portfolio portfolio;
...

@Entity
@org.hibernate.annotations.GenericGenerator(name="performer-primarykey", strategy="foreign",
       parameters={@org.hibernate.annotations.Parameter(name="property", value="performer") })
public class Portfolio implements Serializable
{
   @Id
   @GeneratedValue(generator = "performer-primarykey")
   @Column(name = "portfolio_id")
   private Long id;

   @Column(length = 128)
   private String posterFileName;
   
   @OneToOne
   @PrimaryKeyJoinColumn
   private Performer performer;
...

2455 [main] INFO  org.springframework.context.support.GenericApplicationContext  - Bean 'entityManagerFactory' of type [class org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying)
2706 [main] INFO  org.springframework.test.context.transaction.TransactionalTestExecutionListener  - Began transaction (1): transaction manager [org.springframework.orm.jpa.JpaTransactionManager@42d134d0]; rollback [false]
2765 [main] WARN  org.springframework.test.context.TestContextManager  - Caught exception while allowing TestExecutionListener [org.springframework.test.context.transaction.TransactionalTestExecutionListener@76898587] to process 'after' execution for test: method [public void net.deepthought.next.domain.service.PerformerServiceTest.testPersist()], instance [net.deepthought.next.domain.service.PerformerServiceTest@3e9d9edd], exception [org.springframework.orm.hibernate3.HibernateSystemException: attempted to assign id from null one-to-one property [net.deepthought.next.domain.entity.Portfolio.performer]; nested exception is org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property [net.deepthought.next.domain.entity.Portfolio.performer]]
org.springframework.transaction.TransactionSystemException: Could not commit JPA transaction; nested exception is javax.persistence.RollbackException: Transaction marked as rollbackOnly
   at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:476)