Trying to write a basic EJB app w/ JPA and remote client

Question

I'm trying to put together a simple sample app that shows a simple stateless session bean that grabs a Java EE 5 entity from the DB and sends it to the remote caller. I have an entity class called Person that simply has getId() and getName() methods.
I'm trying to get a reference to the session bean (using InitialContext.lookup()), which works. Then I try to call a method on that bean, which works as long as the type being returned is not a Person object. I've had the bean always return "Hello" and it works just fine.
Here's the bean code.
@Stateless(mappedName="RolodexSession")
public class RolodexSessionBean implements RolodexSessionRemote {
    @PersistenceContext
    private EntityManager em;
    /** Creates a new instance of RolodexSessionBean */
    public RolodexSessionBean() {
    public Object getPersonByName(String name)
        Query q = em.createQuery("select object(o) from Person o where o.name=:n");
        q.setParameter("n",name);
        List results = q.getResultList();
        if (results.isEmpty())
            return "emtpy";
        // this would work just fine...
        // return "Some string";
        // but this doesn't work at all
        return results.get(0);
}Here's the client code...
public class Main {
    @EJB
    protected RolodexSessionRemote rolodexSession;
    /** Creates a new instance of Main */
    public Main() throws NamingException {
        Context ctx = new InitialContext();
        rolodexSession = (RolodexSessionRemote)ctx.lookup("RolodexSession");
        Object result = rolodexSession.getPersonByName("John Smith");
        System.out.println(result);
     * @param args the command line arguments
    public static void main(String[] args) throws NamingException {
        Main m = new Main();
}I made sure to put a Person object into my database with the name "John Smith".
The error I keep getting is...
Dec 7, 2006 4:40:29 PM com.sun.corba.ee.impl.encoding.CDRInputStream_1_0 read_value
WARNING: "IOP00810257: (MARSHAL) Could not find class"
org.omg.CORBA.MARSHAL:   vmcid: SUN  minor code: 257 completed: Maybe
        at com.sun.corba.ee.impl.logging.ORBUtilSystemException.couldNotFindClass(ORBUtilSystemException.java:8309)
        at com.sun.corba.ee.impl.encoding.CDRInputStream_1_0.read_value(CDRInputStream_1_0.java:984)
        at com.sun.corba.ee.impl.encoding.CDRInputStream.read_value(CDRInputStream.java:259)
        at com.sun.corba.ee.impl.io.IIOPInputStream.inputObjectField(IIOPInputStream.java:1987)
        at com.sun.corba.ee.impl.io.IIOPInputStream.inputClassFields(IIOPInputStream.java:2211)
        at com.sun.corba.ee.impl.io.IIOPInputStream.inputObject(IIOPInputStream.java:1219)
        at com.sun.corba.ee.impl.io.IIOPInputStream.simpleReadObject(IIOPInputStream.java:398)
        at com.sun.corba.ee.impl.io.ValueHandlerImpl.readValueInternal(ValueHandlerImpl.java:329)
        at com.sun.corba.ee.impl.io.ValueHandlerImpl.readValue(ValueHandlerImpl.java:295)
        at com.sun.corba.ee.impl.encoding.CDRInputStream_1_0.read_value(CDRInputStream_1_0.java:1005)
        at com.sun.corba.ee.impl.encoding.CDRInputStream_1_0.read_value(CDRInputStream_1_0.java:850)
        at com.sun.corba.ee.impl.encoding.CDRInputStream.read_value(CDRInputStream.java:255)
        at com.sun.corba.ee.impl.corba.TCUtility.unmarshalIn(TCUtility.java:269)
        at com.sun.corba.ee.impl.corba.AnyImpl.read_value(AnyImpl.java:558)
        at com.sun.corba.ee.impl.encoding.CDRInputStream_1_0.read_any(CDRInputStream_1_0.java:710)
        at com.sun.corba.ee.impl.encoding.CDRInputStream.read_any(CDRInputStream.java:225)
        at com.sun.corba.ee.impl.javax.rmi.CORBA.Util.readAny(Util.java:449)
        at com.sun.corba.ee.impl.presentation.rmi.DynamicMethodMarshallerImpl$10.read(DynamicMethodMarshallerImpl.java:251)
        at com.sun.corba.ee.impl.presentation.rmi.DynamicMethodMarshallerImpl.readResult(DynamicMethodMarshallerImpl.java:424)
        at com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.privateInvoke(StubInvocationHandlerImpl.java:162)
        at com.sun.corba.ee.impl.presentation.rmi.StubInvocationHandlerImpl.invoke(StubInvocationHandlerImpl.java:119)
        at com.sun.corba.ee.impl.presentation.rmi.bcel.BCELStubBase.invoke(BCELStubBase.java:197)
        at session.__RolodexSessionRemote_Remote_DynamicStub.getPersonByName(__RolodexSessionRemote_Remote_DynamicStub.java)
        at session._RolodexSessionRemote_Wrapper.getPersonByName(session._RolodexSessionRemote_Wrapper.java)
        at clientapp.Main.<init>(Main.java:33)
        at clientapp.Main.main(Main.java:41)I'm running this on the Sun Java System App Server 9.0.
Any ideas?

Answer 1

I've narrowed down the issue. The Person object that I'm trying to send back has a one-to-many relationship with Address objects. I have this all setup correctly, I think. Here's the code from Person.java that establishes that relationship.
     * Holds value of property addresses.
    @OneToMany(mappedBy = "person")
    private List<Address> addresses;
     * Getter for property addresses.
     * @return Value of property addresses.
    public List<Address> getAddresses() {
        return this.addresses;
     * Setter for property addresses.
     * @param addresses New value of property addresses.
    public void setAddresses(List<Address> addresses) {
        this.addresses = addresses;
    }In Address.java I have the other side of the relationship defined (again, correctly, I think).
IF I COMMENT OUT THIS RELATIONSHIP EVERYTHING WORKS! So, the problem seems to be related to using foreign key associations. Is there something I'm missing here? Perhaps it's related to lazy-loading of foreign keys?