Question

I know downcasting is not doable. But I am trying to work around it.

This is what I have.

public class Ticket{
   public int number;
   public String description;
}

public class MyTicket extends Ticket{
   public String status;
}

But in my app, I want to use the MyTicket class because I don’t want to force the original Ticket object to change. So when the Ticket object comes back from a call (webservice, DB, etc), I try to downcast to a MyTicket and it fails obviously.

MyTicket mt=(MyTicket)ws.getTicket(1234);

So I was trying to figure a way around this. I was thinking of writing a “copyAttributes” method or copy the attributes within the constructor of the MyTicket class, something like this:

MyTicket mt=new MyTicket(ws.getTicket(1234));

public class MyTicket extends Ticket {
    public String status;
    public MyTicket(Ticket tckt){
        //copy tckt attributes to MyTicket attributes
    }
}

Is there a way to get the attributes of a class and set them into another class?
Or is there a totally different way to downcast and I’m missing it?

*SOLUTION:*So I took the solution below and came up with this. I needed the change to return null if the main ticket is not found before the transfer happens:

public class MyTicket extends Ticket {
    public String status;
    public MyTicket(){}
    public static MyTicket newInstance(Ticket tckt){
        MyTicket mytkt=null;
        if(tckt!=null){//copy tckt attributes to MyTicket attributes
            BeanUtilsBean.getInstance().getConvertUtils().register(false,true,-1);
            mytkt = new MyTicket();
            BeanUtils.copyProperties(mytkt, tckt);
        }
        return mytkt;
    }
}

Answer 1

I think you are doing right. If your object grows, you may want to use Apache BeanUtils to assist you in attrbute copying.