The document outlines a lecture on Remote Method Invocation (RMI) in distributed systems, presenting two examples: a login system and a book management system. The first example demonstrates a login server implementation allowing users to authenticate with a username and password, while the second example features a bookstore service that allows users to search for books or view all available titles. Code snippets and explanations for both server and client components are provided to illustrate the RMI functionality.

1. Distributed Systems
Lecture -5-
Created by :
Eng. Ghadeer Al Hasan
RMI
Remote Method Invocation

2. Intro 1
Today we havetwo simple examples
- 1st : a programallows the userto log in to the server
- 2nd : a programallows the userto viewbooks fromthe server and query them

3. 1st Example : LogInRMI

4. Server 3
public interface loginFacade extends Remote{
public String login(String username, String password) throws RemoteException;
}
public class LoginServer extends UnicastRemoteObject implements loginFacade{
private TreeMap clients = new TreeMap<String,String>();
public LoginServer() throws RemoteException{
super();
}
@Override
public String login(String username, String password) throws RemoteException {
Init();
String response = search(username, password);
return response;
}

5. Server… 4
private void Init() {
clients.put("user1", "1234");
clients.put("user2","1234");
}
private String search(String username,String password){
String response ="";
Set set = clients.entrySet();
Iterator it = set.iterator();
boolean flag = false;
while(it.hasNext()){
response ="";
Map.Entry me = (Map.Entry) it.next();
String user = me.getKey().toString();
String pass = me.getValue().toString();
if(username.equalsIgnoreCase(user)){
flag = true;
if(password.equalsIgnoreCase(pass)){
response ="LOGIN_SUCCESFUL";
}else{
response = "PASSWORD_INCORRECT";
}
break;
}
}
if(!flag){
response = "USER_NOT_EXISTS";
}
return response;
}

6. Server… 5
public static void main(String[] args){
try{
Registry reg = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
LoginServer obj = new LoginServer();
reg.rebind("rmi://localhost/service", obj);
System.out.println("Server Running...");
}catch(RemoteException ex){
System.out.println(ex);
}
}

7. Client 6
public class Client {
public static void main(String[] args) {
try{
Registry reg = LocateRegistry.getRegistry("localhost", 1099);
loginFacade server = (loginFacade) reg.lookup("rmi://localhost/service");
Scanner scan = new Scanner(System.in);
System.out.println("Enter username : ");
String username = scan.nextLine();
System.out.println("Enter password : ");
String password = scan.nextLine();
String response = server.login(username, password);
System.out.println("Message From Server : " + response);
}catch(RemoteException | NotBoundException ex){
System.out.println(ex);
}
}
}

8. Run 7

9. 2nd Example : BookRMI

10. 9
public class Book implements Serializable{
private static final long serialVersionUID = 1190476516911661470L;
private String title;
private String code;
private double cost;
public Book(String code) {
this.code = code;
}
public Book(String title, String isbn, double cost) {…}
public String getTitle() {…}
public String getCode() {…}
public double getCost() {…}
public String toString() {
return "> " + this.title + " ($" + this.cost + ")";
}
}
Server

11. 10
public interface BookInterface extends Remote {
Book findBook(Book b) throws RemoteException;
List<Book> allBooks() throws RemoteException;
}
public class BookStore extends UnicastRemoteObject implements BookInterface {
private static final long serialVersionUID = 1L;
private List<Book> bookList;
protected BookStore(List<Book> list) throws RemoteException {
super();
this.bookList = list;
}
Server…

12. 11
@Override
public Book findBook(Book book) throws RemoteException {
Predicate<Book> predicate = x -> x.getCode().equals(book.getCode());
return bookList.stream().filter(predicate).findFirst().get();
}
@Override
public List<Book> allBooks() throws RemoteException {
return bookList;
}
private static List<Book> initializeList() {
List<Book> list = new ArrayList<>();
list.add(new Book("Head First Java, 2nd Edition", "A1", 31.41));
list.add(new Book("Java In A Nutshell", "A2", 10.90));
list.add(new Book("Java: The Complete Reference", "B1", 40.18));
list.add(new Book("Head First Servlets and JSP", "B2", 35.41));
list.add(new Book("Java Puzzlers: Traps, Pitfalls", "C1", 39.99));
return list;
}
Server…

13. 12
public static void main(String[] args) {
try {
Registry reg = LocateRegistry.createRegistry(Registry.REGISTRY_PORT);
BookStore store = new BookStore(initializeList());
reg.rebind("rmi://localhost/service", store);
System.err.println("Server ready");
} catch (Exception e) {
System.err.println("Server exception: " + e.getMessage());
}
}
Server…

14. 13
public class Client {
private static BookInterface server;
public static void main(String[] args) {
try {
Registry reg = LocateRegistry.getRegistry("localhost", 1099);
server = (BookInterface) reg.lookup("rmi://localhost/service");
boolean findmore;
do {
String[] options = {"Show All", "Find a book", "Exit"};
int choice = JOptionPane.
showOptionDialog(null, "Choose an action", "Option dialog",
JOptionPane.DEFAULT_OPTION,
JOptionPane.INFORMATION_MESSAGE,
null, options, options[0]);
Client

15. 14
switch (choice) {
case 0:
List<Book> list = server.allBooks();
StringBuilder message = new StringBuilder();
list.forEach(x -> {
message.append(x.toString() + "n");
});
JOptionPane.showMessageDialog(null, new String(message));
break;
Client…
case 1:
String code= JOptionPane
.showInputDialog("Type the code of the book you want to find.");
try {
Book response = server.findBook(new Book(code));
JOptionPane.showMessageDialog(null, "Title: "
+ response.getTitle() + "n" + "Cost: $"
+ response.getCost(),
response.getCode(), JOptionPane.INFORMATION_MESSAGE);
} catch (NoSuchElementException ex) {
JOptionPane.showMessageDialog(null, "Not found");
}
break;
default:
System.exit(0);
break;
}
findmore = (JOptionPane.showConfirmDialog(null, "Do you want to exit?",
"Exit",JOptionPane.YES_NO_OPTION) == JOptionPane.NO_OPTION);
} while (findmore);
} catch (RemoteException | NotBoundException ex) {
System.out.println(ex);
}
}
}

16. 15Run

17. References 16
- YouTube link
https://www.youtube.com/playlist?list=PLtDIUAtyP4lhV7CsYfLuIx26UeG4J-ujZ
- GitHub
https://github.com/Ghadeerof

18. End Lecture