sending data stored inside an ArrayList via RMI

Question

If I want the client to request text data stored inside an ArrayList in the server, how the process of implementation will be using Java RMI ?

A class diagram or a sample code will be great please.

Answer 1

Define an interface for both server and client (same package name)

package arrayListRMI;

import java.rmi.Remote;
import java.rmi.RemoteException;
import java.util.ArrayList;

public interface IArrayList extends Remote {
    public ArrayList<String> getText()  throws RemoteException;
    public void setText(ArrayList<String> text) throws RemoteException;
}

Define a utility class Constants.java

package arrayListRMI;

public class Constants {    
    public static final String RMI_ID = "StackOverflowAnswer";
    public static final int RMI_PORT = 222 ;   
}

Add an implementation for IArrayList (in the server side)

package arrayListRMI;

import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.ArrayList;


public class ArrayListImpl  extends UnicastRemoteObject implements IArrayList{

    private static final long serialVersionUID = 1L;
    private ArrayList<String> text;

    protected ArrayListImpl() throws RemoteException {
        super();
    }

    public ArrayList<String> getText() {
        return text;
    }

    public void setText(ArrayList<String> text) {
        this.text = text;
    }

}

So you can instantiate an ArrayList of String (text) in the server side by instantiating an ArrayListImpl and bind it to the rmiregistry so that the client can request for it anytime.

ArrayList<String> textRequested = new ArrayList<String>();
textRequested.add("example1");
textRequested.add("example2");
ArrayListImpl arrayListToSend = new ArrayListImpl();
arrayListToSend.setText(textRequested);

Server

package arrayListRMI;

import java.rmi.AlreadyBoundException;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.sql.SQLException;


public class Server {
    public static void main(String args[]) throws AlreadyBoundException, SQLException, ClassNotFoundException {

        try {
            ArrayList<String> textRequested = new ArrayList<String>();
            textRequested.add("example1");
            textRequested.add("example2");
            ArrayListImpl arrayListToSend = new ArrayListImpl();
            arrayListToSend.setText(textRequested);
            Registry registry = LocateRegistry.createRegistry(Constants.RMI_PORT);
            registry.bind(Constants.RMI_ID, arrayListToSend);
            System.out.println("Server starts....");
        } catch (RemoteException e) {
            e.printStackTrace();
        }
    }
}

Client

package arrayListRMI;

import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.util.ArrayList;

public class Client {
    public static void main(String[] args) {
        try {
            Registry registry = LocateRegistry.getRegistry("localhost", Constants.RMI_PORT);
            IArrayList cmp = (IArrayList) registry.lookup(Constants.RMI_ID);
            ArrayList<String> received = cmp.getText();
            System.out.println(received);
        } catch (Exception e) {
            System.err.println("Client exception: " + e.toString());
            e.printStackTrace();
        }
    }
}

Now run the server. You get this output

Server starts....

Then run the client. You get this output

[example1, example2]