File sharing with my chat RMI program - chat

Question

I have been doing a RMI chat system on school and wanted some sort of file sharing with it. Have not done something like this before and have not been through this at school, but I wanted to try. Have done some searching on google and this
http://java.sun.com/developer/technicalArticles/RMI/rmi_corba/
was the best i found. Is this "technology" new so i can use it? Did not get it to work, but that can be my lack of Java knowledge.
Some tips why i don't get it to work?

Answer 1

There isn't a tremendous difference between sending messages back and forth and sending files. The answer depends largely on what your current code looks like. Do you have some code to share?
What does your current RMI interface look like? What does your architecture look like?
Do you have a server that clients connect to?
Do you have a method sendChat(String message)?
With respect to having sendChat(), you could probably add a sendFile( ... ). Then the question is just what you want to do for the parameters.
Do you want to send a java.io.File object? A byte[] (along with a String name, maybe a boolean flag to distinguish binary files)?
Seeing that this is your first time doing this, you might want to code the mundane parts yourself. However, tasks like obtaining bytes from a file are rather common annoyances. The Apache commons and Google guava libraries both provide methods to simplify the process. I suppose it depends on the learning goals you have on this project.

Answer 2

Yes. The clients connects to the server, and are able to chat in chatrooms.
Here is some of the code we have until now, except the file for connecting and communication with the database, and the GUI. Thanks for answering.
Interfaces:
Chatfront interface:
public interface ChatFront extends Remote {
boolean registerClient(Client client, String password) throws RemoteException;
void logMeOut(Client client) throws RemoteException;
void newChannelMessage(String toChannel, String fromUser, String message) throws RemoteException;
void newPrivateMessage(String fromUser, String toUser, String message) throws RemoteException;
String connectChannel(String username, String channel) throws RemoteException;
String disconnectChannel(String username, String channel) throws RemoteException;
boolean isUserRegistered(String username) throws RemoteException;
void errorMessage(String toUser, String message) throws RemoteException;
}
Clientinterface:
public interface Client extends Remote {
String findName() throws RemoteException;
void newPrivateMessage(String fromUser, String toUser, String message) throws RemoteException;
void newMessageChannel(String toChannel, String fromUser, String message) throws RemoteException;
void newSystemMessageChannel(String toChannel, String fromUser, String message) throws RemoteException;
void errorMessage(String toUser, String message) throws RemoteException;
}
Serverside:
class ChatServer {
public static void main(String[] args) throws Exception {
String objectname = "chatter";
LocateRegistry.createRegistry(1099);
ChatFront cf = new ChatFrontImpl();
Naming.rebind(objectname, cf);
javax.swing.JOptionPane.showMessageDialog(null, "Tjener kjører. Trykk OK for å avslutte tjeneren.");
Naming.unbind(objectname);
System.exit(0);
}
}
ChatFrontImpl.java
package server;
import Interfaces.ChatFront;
import Interfaces.Client;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Hashtable;
/**
*
* #author sindre
*/
class ChatFrontImpl extends UnicastRemoteObject implements ChatFront {
private UserDAC u = new UserDAC();
private Hashtable<String, ArrayList<String>> channels = new Hashtable<String, ArrayList<String>>();
private ArrayList<Client> clients = new ArrayList<Client>();
public ChatFrontImpl() throws RemoteException {
}
/* Registrerer en ny client */
#Override
public synchronized boolean registerClient(Client client, String password) throws RemoteException {
if(!u.logIn(client.findName(), password)){
System.out.println("feil username eller password");
return false;
}
if (!clients.contains(client)) {
try {
clients.add(client);
System.out.println("Na er " + client.findName() + " registrert.");
} catch (Exception e){
System.out.println("Feil oppstatt i registrerMeg(): " + e);
}
return true;
} else
return false;
}
/* Kobler en client til en kanal */
#Override
public String connectChannel(String username, String kanal) throws RemoteException{
if(isUserRegistered(username)){
if (!channels.containsKey(kanal)) {
String message = "Bruker " + username + " har ankommet kanalen";
channels.put(kanal, new ArrayList<String>());
channels.get(kanal).add(username);
notifyChannelSystem(kanal, "SYSTEM", message);
notifySelf(username, "Skriv /? for mulige kommandoer");
return("Kanal opprettet, og bruker satt i kanalen.");
}
else{
if(channels.get(kanal).contains(username)){
return ("Brukeren er allerede i kanalen.");
} else {
channels.get(kanal).add(username);
String message = "Bruker " + username + " har ankommet kanalen";
notifyChannelSystem(kanal, "SYSTEM", message);
return ("Kanal fantes allerede. Bruker satt i kanalen.");
}
}
}
return "";
}
/*Sjekker om brukeren ikke er blank.*/
#Override
public boolean isUserRegistered(String username){
if(username.equals("")){
return false;
}
return true;
}
/* Kobler en bruker fra en kanal */
#Override
public String disconnectChannel(String username, String channel) throws RemoteException{
if(isUserInChannelX(username, channel)){
channels.get(channel).remove(username);
String message = "Bruker " + username + " har forlatt kanalen.";
notifySelf(username, " Du har nå forlatt kanalen " + channel);
notifyChannelSystem(channel, "SYSTEM", message);
if(channels.get(channel).isEmpty()){
channels.remove(channel);
}
}
return ("Bruker har forlatt kanalen.");
}
/* Kobler en client fra clientlisten */
#Override
public synchronized void logMeOut(Client client) throws RemoteException {
boolean isfound = false;
int clientIndeks = 0;
while (clientIndeks < clients.size() && !isfound) {
Client denne = clients.get(clientIndeks);
if (denne.equals(client)) { // bruker equals() for a sammenlikne stubbobjektene
isfound = true;
clients.remove(clientIndeks);
System.out.println("Na er clienten " + client.findName() + " fjernet.");
} else clientIndeks++;
}
}
/* Sjekker om brukeren finnes i en gitt kanal */
public boolean isUserInChannelX(String bruker, String kanal){
if(channels.containsKey(kanal) && channels.get(kanal).contains(bruker)){
return true;
} else {
return false;
}
}
/* Kaller metoden varsleKanal()*/
#Override
public void newChannelMessage(String tilKanal, String fraBruker, String message) throws RemoteException{
if(isUserInChannelX(fraBruker, tilKanal)){
notifyChannel(tilKanal, fraBruker, message);
}
else{
}
}
/* Kaller metoden varsleEn() */
#Override
public void newPrivateMessage(String fra, String toUser, String message) throws RemoteException{
notifyUser(fra,toUser,message);
}
#Override
public void errorMessage(String toUser, String message) throws RemoteException{
notifySelf(toUser, message);
}
private void notifySelf(String toUser, String message) throws RemoteException{
for(Client k: clients){
if(k.findName().equals(toUser)){
k.errorMessage(toUser, message);
}
}
}
/* Bruker metoden nymessagePrivat() + ser om brukeren er tilkoblet*/
private void notifyUser(String fromUser, String toUser, String message) throws RemoteException{
boolean funnet = false;
for(Client k : clients){
if(k.findName().equals(toUser)){
k.newPrivateMessage(fromUser, toUser, message);
funnet = true;
}
}
if (!funnet) errorMessage(fromUser, "Ingen brukere ved dette navnet!");
}
/* Kjører metoden nymessageKanal() */
private void notifyChannel(String toChannel, String fromUser, String message) throws RemoteException{
if(channels.containsKey(toChannel) && isUserRegistered(fromUser)){
for(String k : channels.get(toChannel)){
for(Client cli : clients){
if(cli.findName().equals(k)){
cli.newMessageChannel(toChannel, fromUser, message);
}
}
}
}
else{
System.out.println("Brukeren er ikke registrert.");
}
}
private void notifyChannelSystem(String toChannel, String fromUser, String message) throws RemoteException{
if(channels.containsKey(toChannel) && isUserRegistered(fromUser)){
for(String k : channels.get(toChannel)){
for(Client kli : clients){
if(kli.findName().equals(k)){
kli.newMessageChannel(toChannel, fromUser, message);
}
}
}
}
else{
System.out.println("Brukeren er ikke registrert.");
}
}
}
Clientside:
GUILogic.java
package gui;
import Interfaces.ChatFront;
import Interfaces.Client;
import java.rmi.Naming;
import java.rmi.RemoteException;
import klient.ClientImpl;
/**
*
* #author sindre
*/
public class GUILogic {
GUI gui;
ChatFront cf;
public String username;
public String channel;
public String password;
public String message;
public GUILogic(GUI gui){
this.gui = gui;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getChannel() {
return channel;
}
public void setChannel(String channel) {
this.channel = channel;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
/* Kobler GUI klienten opp mot serveren */
public void createCFConnection(String username, String password) throws Exception{
String objectname = "chatter";
String hostname = "localhost";
String url = "rmi://" + hostname + "/" + objectname;
cf = (ChatFront) Naming.lookup(url);
Client k = new ClientImpl(username, gui);
cf.registerClient(k, password);
}
public void connectChannel(String username, String channel) throws RemoteException{
cf.connectChannel(username, channel);
}
public void disconnectChannel(String username, String channel) throws RemoteException{
cf.disconnectChannel(username, channel);
}
public void newChannelMessage(String toChannel, String fromUser, String message) throws RemoteException{
cf.newChannelMessage(fromUser ,toChannel, message);
}
public void newPrivateMessage(String fromUser, String toUser, String message) throws RemoteException{
cf.newPrivateMessage(fromUser, toUser, message);
}
public void errorMessage(String toUser, String message) throws RemoteException{
cf.errorMessage(toUser, message);
}
/* Logger klienten av GUIen */
public boolean logOut(String username) throws RemoteException{
Client k = new ClientImpl(username, gui);
if(k.findName().equals("")){
return false;
} else {
cf.logMeOut(k);
System.out.println("user " + username + " logget ut.");
return true;
}
}
/* Analysermessage har funnet / i starten av messageen, og da blir denne metoden kjørt. */
public String commandWritten(String username, String channel, String message) throws RemoteException{
String[] result = message.split(" ", 3);
String channel1;
if((result[0].equalsIgnoreCase("/join") || (result[0].equalsIgnoreCase("/j")))){
channel1 = result[1];
setChannel(channel1);
connectChannel(username, channel1);
}
else if(result[0].equalsIgnoreCase("/leave") || (result[0].equalsIgnoreCase(("/l")))){
channel = result[1];
disconnectChannel(username, channel);
}
else if(result[0].equalsIgnoreCase("/whisper") || (result[0].equalsIgnoreCase(("/w")))){
for (int x=2; x<result.length; x++)
newPrivateMessage(username, result[1], result[x]);
}
else if(result[0].equalsIgnoreCase("/exit") || (result[0].equalsIgnoreCase(("/e")))){
System.exit(0);
}
else if(result[0].equalsIgnoreCase("/?")){
errorMessage(username, "Mulige kommandoer er:" + "\n" +
"/leave 'channel' eller /l" + "\n" +
"/whisper 'username' eller /w" + "\n" +
"/join 'channel' eller /j" + "\n" +
"/exit eller /e" + "\n");
}
else{
errorMessage(username, "Feil kommando! Skriv /? for mulige kommandoer");
}
return message;
}
/* Analyserer messageen som skrives inn i messagefeltet. Kommandoer starter med / */
public void analyzeMessage(String username, String channel, String message) throws RemoteException{
String text = getMessage().toLowerCase();
char command = '/';
for(int i = 0; i<1; i++){
char c = text.charAt(0);
if(c == command){
commandWritten(username, channel, text);
}
else {
newChannelMessage(username, channel, text);
}
}
}
}