@Entity
@Table (name = "USER")
public class User {

private int userId;
private List<User> children;
private User parentUser;


@Id
@Column(name = "USER_ID", length = 4)
public int getUserId()
{
   return userId;
}

@OneToMany(mappedBy = "parentuser", targetEntity = User.class)
  public List<User> getChildren()
  {
    return this.getChildren();
  }

@ManyToOne( fetch = FetchType.LAZY, cascade = {CascadeType.PERSIST, CascadeType.MERGE}, targetEntity = User.class )
@JoinColumn(name="DEPEND_USER_ID", insertable = true, updatable = true)
public User getParentUser()
{
return parentUser;
}
   
}

org.springframework.dao.InvalidDataAccessApiUsageException: object references an unsaved transient instance - save the transient instance before flushing: com.domain.User; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.domain.User
Caused by: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.domain.User
   at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:219)
   at org.hibernate.type.EntityType.getIdentifier(EntityType.java:397)
   at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:242)
   at org.hibernate.type.TypeFactory.findDirty(TypeFactory.java:563)
   at org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:3071)
   at org.hibernate.event.def.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:472)
   at org.hibernate.event.def.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:197)
   at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:120)
   at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:196)
   at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
   at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
   at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:615)
   at org.springframework.orm.hibernate3.HibernateTemplate$CloseSuppressingInvocationHandler.invoke(HibernateTemplate.java:1197)
   at $Proxy28.flush(Unknown Source)
   at com.fsg.fedad.test.dbunit.HibernateDbUnitTemplate$2.doInHibernate(HibernateDbUnitTemplate.java:65)
   at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:367)
   at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:333)
   at com.fsg.fedad.test.dbunit.HibernateDbUnitTemplate.flush(HibernateDbUnitTemplate.java:70)
   at com.unittest.TestUserTasks.testUpdateUser(TestUserTasks.java:248)
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:64)
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
   at java.lang.reflect.Method.invoke(Method.java:615)
   at junit.framework.TestCase.runTest(TestCase.java:154)
   at junit.framework.TestCase.runBare(TestCase.java:127)
   at com.fsg.fedad.test.DataAccessTierTestCase.runBare(DataAccessTierTestCase.java:109)
   at junit.framework.TestResult$1.protect(TestResult.java:106)
   at junit.framework.TestResult.runProtected(TestResult.java:124)
   at junit.framework.TestResult.run(TestResult.java:109)
   at junit.framework.TestCase.run(TestCase.java:118)
   at junit.framework.TestSuite.runTest(TestSuite.java:208)
   at junit.framework.TestSuite.run(TestSuite.java:203)
   at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:128)
   at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
   at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)

public List<User> getChildren()
  {
    return this.getChildren();
}