Hi Guys, this is my environment: java 1.6 jboss-version: 4.0.5.GA Seam-Version: 1.2.1.GA Hibernate-Version: 3.2.3.ga I' m using annotation and javax.persistence.EntityManager. the problem is in the mapping of the following schema (the relation are all one-to-one): First <-(Fk to First)-Second <-(Fk to Second)-Third .First has a pk generated by a sequence. .Second and Third tables have pk=fk this is my mapping: ======================= public class EBFirst implements java.io.Serializable { private EBSecond eBSecond; @GenericGenerator(name="generator", strategy="myGenerator.TriggerGenerator") @Id @GeneratedValue(generator="generator") @Column(name="PK_ID", unique=true, nullable=false, columnDefinition="NUMBER", precision=28, scale=0) public BigDecimal getPkId() { return this.pkId; } @OneToOne(mappedBy="EBFirst", cascade=CascadeType.ALL) public EBSecond getEBSecond() { return eBSecond; } . . . } ------------ public class EBSecond implements java.io.Serializable { private EBFirst EBFirst; private EBThird eBThird; @GenericGenerator(name="generator", strategy="foreign", parameters = {@Parameter(name = "property", value = "EBFirst")}) @GeneratedValue(generator="generator") @Id @Column(name="PK_ID", unique=true, nullable=false, columnDefinition="NUMBER", precision=28, scale=0) public BigDecimal getPkId() { return this.pkId; } @OneToOne @PrimaryKeyJoinColumn public EBFirst getEBFirst() { return this.EBFirst; } @OneToOne (mappedBy="EBSecond", cascade=CascadeType.ALL) public EBThird getEBThird() { return eBThird; } . . . } ------------- public class EBThird implements java.io.Serializable { @GenericGenerator(name="generator", strategy="foreign", parameters = {@Parameter(name = "property", value = "EBSecond")}) @GeneratedValue(generator="generator") @Id @Column(name="PK_ID", unique=true, nullable=false, columnDefinition="NUMBER", precision=28, scale=0) public BigDecimal getPkId() { return this.pkId; } @OneToOne @PrimaryKeyJoinColumn public EBSecond getEBSecond() { return this.EBSecond; } . . . } ======================= this is the exception at startup: [org.jboss.system.ServiceController] Problem starting service persistence.units:ear=cerssvd.ear,jar=cerssvd.ejb3.jar,unitName=entityManager java.lang.NullPointerException at org.hibernate.cfg.OneToOneSecondPass.doSecondPass(OneToOneSecondPass.java:135) at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1054) at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:296) at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1039) at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1211) at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:154) at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:847) at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:385) at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:126) at org.jboss.ejb3.entity.PersistenceUnitDeployment.start(PersistenceUnitDeployment.java:264) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) . . . the problem is in the class EBSecond at the following: @OneToOne (mappedBy="EBSecond", cascade=CascadeType.ALL) he doesn't like the attribute mappedBy="EBSecond". But it's mandatory (in this context) Can someone help me? Thanks, Gianpaolo View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4095544#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...