Please Help

[Gowher Naik]

Can anyone please provide a simple example for Entity bean with Container managed relationship.
I tried google search but could not find any example.

Thanks

[Gowher Naik]

Please provide one to many relationship example.
Thanks

[Jonny Andersson]

The complicated things is not that much in the code but in how to successfully get it deployed. But okay, here is an example on a little bean with CMP for securities (stocks) which I have been able to deploy in the J2EE 1.3 RI app server from Sun.

The home interface:

package stockadmin.ejb;
 
import java.rmi.RemoteException;
import javax.ejb.CreateException;
import javax.ejb.EJBHome;
import javax.ejb.FinderException;
 
/**
 * A home for security entities.
 */
public interface SecurityHome extends EJBHome
{
    /**
     * Creates a new security.
     *
     * @param id the id for this security.
     * @param name the name of the new security.
     * @return the created security entity.
     * @throws CreateException if failed to create the security.
     * @throws RemoteException if an error occurred while trying to create the security.
     */
    Security create(String id, String name) throws CreateException, RemoteException;
 
    /**
     * Gets the security with the given id.
     *
     * @param id the id of the security to find.
     * @return the security for the given id.
     * @throws FinderException if failed to find the security with the given id.
     * @throws RemoteException if an error occurred while trying to find the security.
     */
    Security findByPrimaryKey(String id) throws FinderException, RemoteException;
}

The business component interface:

package stockadmin.ejb;
 
 
import java.rmi.RemoteException;
import javax.ejb.EJBObject;
 
 
/**
 * An entity bean to manage persited security.
 */
public interface Security extends EJBObject
{
    /**
     * Gets the name of this security.
     *
     * @return the name of this security.
     * @throws RemoteException  if an error occurred while getting the name of this security.
     */
    String getName() throws RemoteException;
 
 
    /**
     * Assigns a name to this security.
     *
     * @param name the name to assign to this security.
     * @throws RemoteException f an error occurred while trying to assign a name to this security.
     */
    void setName(String name) throws RemoteException;
}

And the code for the bean, which is almost empty:

package stockadmin.ejb.impl;
 
 
import javax.ejb.CreateException;
import javax.ejb.EntityBean;
import javax.ejb.EntityContext;
 
 
public abstract class SecurityBean implements EntityBean
{
    public String ejbCreate(String id, String name)
        throws CreateException
    {
        this.setName(name);
        this.setId(id);
 
        return null;
    }
 
 
    public void ejbPostCreate(String id, String name)
        throws CreateException
    {
    }
 
 
    public void setEntityContext(EntityContext ctx)
    {
    }
 
 
    public abstract String getName();
 
 
    public abstract void setName(String name);
 
 
    public abstract String getId();
 
 
    public abstract void setId(String id);
 
 
    public void unsetEntityContext()
    {
    }
 
 
    public void ejbLoad()
    {
    }
 
 
    public void ejbStore()
    {
    }
 
 
    public void ejbActivate()
    {
    }
 
 
    public void ejbPassivate()
    {
    }
 
 
    public void ejbRemove()
    {
    }
}

Well, we need a client also to be able to see it really happen when we have got the bean deployed. So here is a little client:

package stockadmin.client;
 

import javax.naming.Context;
import javax.naming.InitialContext;
import javax.rmi.PortableRemoteObject;
 
import stockadmin.ejb.Security;
import stockadmin.ejb.SecurityHome;
 

public class Client
{
 
    public static void main(String[] args)
    {
        Client client = new Client();
        client.execute();
    }
 
    public void execute()
    {
        try
        {
            Context ic = new InitialContext();
            Object entity = ic.lookup("SecurityBean");
            SecurityHome home = (SecurityHome) PortableRemoteObject.narrow(entity, SecurityHome.class);
 
            Security stock = null;
            stock = home.create("1", "AstraZeneca");
            stock = home.create("2", "Bilia A");
            stock = home.create("3", "Ericsson");
 
            stock = home.findByPrimaryKey("2");
 
            System.out.println(stock.getName());
        }
        catch (Exception ex)
        {
            ex.printStackTrace();
        }
    }
}

I have got this example to work in the J2EE 1.3 RI app server.

By the way, the named stocks is Swedish stocks
[ June 13, 2007: Message edited by: Jonny Andersson ]

[Jonny Andersson]

But was it not just a CMP bean you asked for for the first time? If you want some beans with CMR do I think you should start by look into a good book, for example HF EJB, or the J2EE 1.3 tutorial from Sun�s site which have some examples. You find their tutorial here http://java.sun.com/j2ee/tutorial/1_3-fcs/ (which can be found using google and the keywords j2ee 1.3 tutorial )
[ June 14, 2007: Message edited by: Jonny Andersson ]

[Gowher Naik]

Thanks Jonny for example
But the example which you have posted is for CMP example and i want example with CMR(1:m).
I am studying HFEJB but the example in book is not complete.
I tried Roster Example but i am not able to understand it.

Please help me.
Thanks

[Jonny Andersson]

That is something that I also have been aware of about the HF EJB book, they have too few examples at least too few complete examples! So I read the most of J2EE 1.3 tutorial to get more examples. I don�t remember if I got the Roster example to work or not but I don�t have time to check it now because I have planed to be finished in about two weeks from now and still have much repetition left to do. Maybe did I get some trouble with the RI app server and skipped spend more time on trying to get it to work.

But if you understand CMP well do I suggest that you just read carefully about CMR as the major difference lies in different virtual accessors for CMR and that you have to use local interfaces for the related beans. I can understand you because I also like too really see things I read about and need to memorize working myself and do some hand on. But it takes a lot of time to try out every thing and at some time must the exam be finished. So I hope that reading the details for CMR should be enough.

Sometimes have I wondered why not a site like this one could have a section where someone could put a little working example (that is well commented and with good code!) with a client on every bean type and so on as so many is trying to learn the same thing. I could consider contribute to it myself.