I use jboss3.0 final and mysql and I created two beans bbs_root_context and bbs_children_conext;
they are descripted in ejb-jar.xml:
<ejb-jar>
<enterprise-beans>

<ejb-name>bbs_root_context</ejb-name>
....
<abstract-schema-name>bbs_root_context</abstract-schema-name>
<cmp-field>
<field-name>root_id</field-name>
</cmp-field>
<cmp-field>
<field-name>user_id</field-name>
</cmp-field>
....



<ejb-name>bbs_children_context</ejb-name>
......
<abstract-schema-name>bbs_children_context</abstract-schema-name>
<cmp-field>
<field-name>child_id</field-name>
</cmp-field>
<cmp-field>
<field-name>root_id</field-name>
</cmp-field>
......

</enterprise-beans>
......

<ejb-relation>
<ejb-relation-name>root-children</ejb-relation-name>
<ejb-relationship-role>

<ejb-relationship-role-name>root-has-children</ejb-relationship-role-name>
One
<relationship-role-source>
<ejb-name>bbs_root_context</ejb-name>
</relationship-role-source>
<cmr-field>
<cmr-field-name>children</cmr-field-name>
<cmr-field-type>java.util.Collection</cmr-field-type>
</cmr-field>
</ejb-relationship-role>
<ejb-relationship-role>

<ejb-relationship-role-name>children-has-root</ejb-relationship-role-name>
Many
<cascade-delete/>
<relationship-role-source>
<ejb-name>bbs_children_context</ejb-name>
</relationship-role-source>
<cmr-field>
<cmr-field-name>root</cmr-field-name>
</cmr-field>
</ejb-relationship-role>
</ejb-relation>

</ejb-jar>
here,root_id is bbs_root_context's primary key;
In jbosscmp-jdbc.xml
......

<ejb-relation>
<ejb-relation-name>root-children</ejb-relation-name>
<foreign-key-mapping/>
<ejb-relationship-role>
<ejb-relationship-role-name>root-has-children</ejb-relationship-role-name>
<key-fields>
<key-field>
<field-name>root_id</field-name>
<column-name>root_id</column-name>
</key-field>
</key-fields>
</ejb-relationship-role>
<ejb-relationship-role>
<ejb-relationship-role-name>children-has-root</ejb-relationship-role-name>
<key-fields/>
</ejb-relationship-role>
</ejb-relation>

....
when I run my test grogram to try to create bbs_root_context bean,I got a exception:
java.rmi.ServerException: RemoteException occurred in server thread; nested exce
ption is:
java.rmi.ServerException: null
Embedded Exception
Could not create entity:java.sql.SQLException: General error: Column 'root_id' s
pecified twice; nested exception is:
javax.ejb.EJBException: null
Embedded Exception
Could not create entity:java.sql.SQLException: General error: Column 'root_id' s
pecified twice
at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:292)
at sun.rmi.transport.Transport$1.run(Transport.java:148)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Transport.java:144)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:4
60)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport
.java:701)
at java.lang.Thread.run(Thread.java:536)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Stream
RemoteCall.java:247)
at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:
223)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:133)
at org.jboss.invocation.jrmp.server.JRMPInvoker_Stub.invoke(Unknown Sour
ce)
at org.jboss.invocation.jrmp.interfaces.JRMPInvokerProxy.invoke(JRMPInvo
kerProxy.java:128)
at org.jboss.invocation.InvokerInterceptor.invoke(InvokerInterceptor.jav
a:108)
at org.jboss.proxy.TransactionInterceptor.invoke(TransactionInterceptor.
java:73)
at org.jboss.proxy.SecurityInterceptor.invoke(SecurityInterceptor.java:7
6)
at org.jboss.proxy.ejb.StatefulSessionInterceptor.invoke(StatefulSession
Interceptor.java:117)
at org.jboss.proxy.ClientContainer.invoke(ClientContainer.java:76)
at $Proxy1.postChildrenConext(Unknown Source)
at Test.Test.runExample(Unknown Source)
at Test.Test.main(Unknown Source)
Caused by: java.rmi.ServerException: null
Embedded Exception
Could not create entity:java.sql.SQLException: General error: Column 'root_id' s
pecified twice; nested exception is:
javax.ejb.EJBException: null


Can any one help me?thank you.