return type polymorphism issue, please help

[beligum]

Hi all, I guess this should be easy for some of you experts, so I hope to get an answer here, after searching for this bug for a couple of hours now.

Here's the situation:

@XmlJavaTypeAdapter(AbstractInodeImpl.Adapter.class)
public interface Inode extends Serializable, Comparable<Inode>, Cloneable
{
 //definition of getters,setters,...
}

@Entity
@Table(name="inode")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(
 name="type",
 discriminatorType=DiscriminatorType.STRING
)

@XmlSeeAlso({FileInode.class, DirectoryInode.class})
public abstract class AbstractInodeImpl implements Inode
{
 //implementation of getters,setters,...

 static public class Adapter extends XmlAdapter<AbstractInodeImpl, Inode>
 {
 public Inode unmarshal(AbstractInodeImpl v)
 {
 return v;
 }
 public AbstractInodeImpl marshal(Inode v)
 {
 return (AbstractInodeImpl)v;
 }
 }
}

@Entity
@Name("directoryInode")
@DiscriminatorValue("directory")
public class DirectoryInode extends AbstractInodeImpl implements Serializable
{
 // more implementation
}

@Entity
@Name("fileInode")
@DiscriminatorValue("file")
public class FileInode extends AbstractInodeImpl implements Serializable
{
 // even more...
}

@Stateless
@WebService(name = "FileSystemService", serviceName = "FileSystemService")
@Name("fileSystemService")
@WebContext(contextRoot="/tumbolia/services", urlPattern="/FileSystemService")
public class FileSystemServiceImpl implements FileSystemService, Serializable
{
 @WebMethod
 public List<Inode> getAllChildren(String inodePath)
 {
 List<Inode> children = ((FileSystemManager)Component.getInstance("fileSystemManager", true)).getInodePathChildren(inodePath);

 return children;
 }
}

I generate my JAXB beans with wsconsume or wsimport (have tried both) from the wsdl that was automatically generated.

When I call the webservice in the last bean, I get this exception:

[javax.xml.bind.UnmarshalException: Unable to create an instance of com.acepostproduction.tumbolia.webservice.AbstractInodeImpl
 - with linked exception:
[java.lang.InstantiationException]]
com.acepostproduction.virtuolia.exceptions.WsException: [TumboliaFileSystemCommunicator] Error while calling getAllChildren(): javax.xml.bind.UnmarshalException
 - with linked exception:
[javax.xml.bind.UnmarshalException: Unable to create an instance of com.acepostproduction.tumbolia.webservice.AbstractInodeImpl
 - with linked exception:
[java.lang.InstantiationException]]
 at com.acepostproduction.virtuolia.communicator.TumboliaFileSystemCommunicator.getAllChildren(TumboliaFileSystemCommunicator.java:87)
 at com.acepostproduction.virtuolia.VirtuoliaDiskDriver.startSearch(VirtuoliaDiskDriver.java:340)
 ...

Any ideas why the polymorphism on the return value is failing?
It would be great if someone could give me a hint here.

bram