Hi,
I have a requirement in my application to use a Parent-Child relation as described below.

Parent : Folder
Child : subFolder or Document

I need to do the following:
1. create the parent alone with out any children
2. create a child alone in an existing parent folder

I used the following relationship mapping

<!-- Folder Model definition -->
<class name="citadon.bizcomponent.dms.model.Folder" table="folder" dynamic-update="true">
<id name="ObjectId" type="string" column="FolderId" unsaved-value="null">

<generator class="assigned"/>
</id>
<set name="ChildDocuments" table="folder" inverse="true" lazy="true">
<key column="FolderId"/>
<one-to-many class="citadon.bizcomponent.dms.model.Document"/>
</set>
<!-- SubFolder to Folder Relation -->
<many-to-one name="ParentFolder" column="ParentId" class="citadon.bizcomponent.dms.model.Folder" lazy="true"/>
<!-- Folder Folder Relation -->
<set name="ChildFolders" table="folder" inverse="true" lazy="true">
<key column="ParentId"/>
<one-to-many class="citadon.bizcomponent.dms.model.Folder"/>
</set>
</class>
<class name="citadon.bizcomponent.dms.model.Document" table="document" dynamic-update="true">
<id name="ObjectId" type="string" column="DocumentId" unsaved-value="null">
<generator class="assigned"/>
</id>
<many-to-one name="ParentFolder" column="FolderId" class="citadon.bizcomponent.dms.model.Folder" lazy="true"/>
</class>

When I tried to create the parent folder alone I am getting a Null Pointer exception for the collection (children). My requirement is that I will not be having any child at the time of creating the parent folder. Is there a way I can tell hibernate create only the parent and ignore creating the children. Also can I tell hibernate create only the child and ignore updating the parent.

I am struck with this issue. Could some one give me a pointer as to what can be done to overcome this issue.

thanks, TM

How about posting the stack trace for this NullPointerException. Hibernate will not care if a collection is null; most likely your code is trying to do something with the collection.

Steve,
Here is the stack trace.

<StackTrace>java.lang.Exception: java.lang.NullPointerException
at net.sf.hibernate.collection.CollectionPersister.writeIndex(CollectionPersister.java:412)
at net.sf.hibernate.collection.ArrayHolder.writeTo(ArrayHolder.java:115)
at net.sf.hibernate.collection.CollectionPersister.recreate(CollectionPersister.java:636)
at net.sf.hibernate.impl.ScheduledCollectionRecreate.execute(ScheduledCollectionRecreate.java:23)
at net.sf.hibernate.impl.SessionImpl.executeAll(SessionImpl.java:2133)
at net.sf.hibernate.impl.SessionImpl.execute(SessionImpl.java:2098)
at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2038)
at net.sf.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:57)
at citadon.platform.global.ProjectnetTransaction.commit(ProjectnetTransaction.java:344)
at citadon.bizcomponent.dms.service.FolderServicesBean.createFolders(FolderServicesBean.java:276)
at citadon.bizcomponent.dms.service.FolderServicesBean_n3ivik_EOImpl.createFolders(FolderServicesBean_n3ivik_EOImpl.java:709)
at citadon.bizcomponent.dms.service.FolderServicesBean_n3ivik_EOImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:305)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:93)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:274)
at weblogic.rmi.internal.BasicServerRef.dispatch(BasicServerRef.java:167)
at weblogic.rmi.internal.ServerRequest.sendOneWayRaw(ServerRequest.java:92)
at weblogic.rmi.internal.ServerRequest.sendReceive(ServerRequest.java:112)
at weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:262)
at weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:229)
at weblogic.rmi.internal.ProxyStub.invoke(ProxyStub.java:35)
at $Proxy250.createFolders(Unknown Source)
at citadon.bizcomponent.dms.adaptor.FolderAdaptor.createFolder(FolderAdaptor.java:253)
at citadon.bizcomponent.dms.adaptor.FolderAdaptor.processRequest(FolderAdaptor.java:152)
at citadon.bizcomponent.dms.adaptor.DmsAdaptor.processRequest(DmsAdaptor.java:64)
at java.lang.reflect.Method.invoke(Native Method)
at citadon.platform.service.projectnetservlet.CitadonSoapServlet.doPost(CitadonSoapServlet.java:200)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:2546)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2260)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)

at citadon.platform.global.ProjectnetTransaction.commit(ProjectnetTransaction.java:361)
at citadon.bizcomponent.dms.service.FolderServicesBean.createFolders(FolderServicesBean.java:276)
at citadon.bizcomponent.dms.service.FolderServicesBean_n3ivik_EOImpl.createFolders(FolderServicesBean_n3ivik_EOImpl.java:709)
at citadon.bizcomponent.dms.service.FolderServicesBean_n3ivik_EOImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:305)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:93)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:274)
at weblogic.rmi.internal.BasicServerRef.dispatch(BasicServerRef.java:167)
at weblogic.rmi.internal.ServerRequest.sendOneWayRaw(ServerRequest.java:92)
at weblogic.rmi.internal.ServerRequest.sendReceive(ServerRequest.java:112)
at weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:262)
at weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:229)
at weblogic.rmi.internal.ProxyStub.invoke(ProxyStub.java:35)
at $Proxy250.createFolders(Unknown Source)
at citadon.bizcomponent.dms.adaptor.FolderAdaptor.createFolder(FolderAdaptor.java:253)
at citadon.bizcomponent.dms.adaptor.FolderAdaptor.processRequest(FolderAdaptor.java:152)
at citadon.bizcomponent.dms.adaptor.DmsAdaptor.processRequest(DmsAdaptor.java:64)
at java.lang.reflect.Method.invoke(Native Method)
at citadon.platform.service.projectnetservlet.CitadonSoapServlet.doPost(CitadonSoapServlet.java:200)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:760)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:265)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:200)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:2546)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2260)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:139)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)

thanks,
TM

The following is the sql trace of the Hibernate.

Hibernate: insert into folder (ObjectName, ObjectType, Name, Revision, VaultName, Policy, ObjectOwner, Grantee, Originated, Modified, Description, LastAction, LastActionDateTime, LastActionUserId, Status, Path, LinkType, OldStatus, CaXML, CaDefnId, Title, LockStatus, SearchKeyword, Notify, ReasonForLock, EntityType, ParentType, ContentObjectType, ElementType, ElementExists, ParentId, SpaceId, FolderId) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
Hibernate: update document set FolderId=null where FolderId=?
Hibernate: update folder set ParentId=null where ParentId=?
Hibernate: update document set FolderId=null where FolderId=?
Hibernate: update folder set ParentId=null where ParentId=?
Hibernate: update folder set ParentId=? where FolderId=?

I am surprised to see the updates for child folders and child documents even though there is no child folder or child document in the parent folder being created.

thanks,
TM

I could not figure out how to prevent the updates to children or querying the children when the transaction is commited for a PARENT-CHILD (one-to-many) relation. Could some one let me know is it possible in hibernate and if so how can this be done. I am kind of struck with this issue as quite a number of our relations are PARENT-CHILD.

thanks,
TM

Please read the documentation. This is covered very explicitly.

This issue was resolved by making the parent-child as bidirectional.
Thanks Gavin.