interview question

[kesava chaitanya]

hi
yesterday i went to one interview;the interviewer asked me one question;(ie) one jsp client is there;he gets bean instance from a pool of bean instanes from container(entity bean);say another jsp(2nd jsp page) is there, he wants same bean instance from the first jsp page without touching container again;i said u can do it using JNDI reference;but the interviewer told me u can do that using handle;Is that possible using Handle;
bye
chaitu

[Marcos Maia]

Hi,
Yes doing this using handle you don�t loose the time to lookup the reference in the jndi tree, there�s a pattern called ServiceLocator that adresses exactly this task, you can use a code like this:

  
/**
* You may use a method like this to recover the remote reference using the handle.
*/
public EJBObject getService(String id)throws ServiceLocatorException
    {
        if(id == null)
        {
            throw new ServiceLocatorException("O id nulo passado n�o � v�lido.");
        }
        try
        {
            byte[] bytes = new String(id).getBytes();
            InputStream entrada = new ByteArrayInputStream(bytes);
            ObjectInputStream objeto_entrada = new ObjectInputStream(entrada);
            Handle handle = (Handle)(objeto_entrada.readObject());
            return(handle.getEJBObject());
        }
        catch(Exception e)
        {
            throw new ServiceLocatorException("Erro ao recuperar EJBObject com id: " + id + "certifique-se " +
                                            "em ter registrado este EJBObject utilizando o m�todo getId " + e.getMessage());
        }
    }
/**
* This method can be used to serialize the handle and give the client and id to recover it.
*/
public String getId(EJBObject ejb_object)throws ServiceLocatorException
    {
        try
        {
            Handle handle = ejb_object.getHandle();
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            ObjectOutputStream objeto_saida = new ObjectOutputStream(bos);
            objeto_saida.writeObject(handle);
            objeto_saida.flush();
            objeto_saida.close();
            return(new String(bos.toByteArray()));
        }
        catch(Exception e)
        {
            throw new ServiceLocatorException("Erro ao serializar o Handle " + e.getMessage());
        }
    }

regards.