PPT Slide

the code

Book

Printer

User

Library

revised

class Book {

private BookID id;

private PostScript ps;

private UserID borrower;

public Book(String t, String a, String i, PostScript p) {

id = new BookID(t,a,i);

ps = p;

}

public UserID get_borrower() {return borrower;}

public void set_borrower(UserID u) {borrower = u;}

public PostScript get_ps() { return ps; }

public BookID get_bid() { return id; }

}

class BookID {

private String title;

private String author;

private String isbn;

public BookID(String t, String a, String i) {

title = t;

author = a;

isbn = i;

}

public String get_title() {return title;}

}

class User {

private UserID id;

Library theLibrary;

Printer thePrinter;

public User(String n) { id = new UserID(n); }

public boolean getBook (String title) {

BookID aBook=null;

try{

aBook = theLibrary.getBook(id, title);

} catch (RemoteException e) {}

try {

thePrinter.print(id, aBook);

} catch (RemoteException e) {}

return true;

}

public UserID get_uid() { return id; }

}

class UserID {

private String name;

public UserID(String n) { name = n; }

public String get_name() { return name; }

}

interface LibraryInterface extends Remote {

public BookID getBook(UserID u, String title) throws RemoteException;

public PostScript getBookPS(BookID bid) throws RemoteException;

}

class Library extends UnicastRemoteObject implements LibraryInterface {

Hashtable books;

Library() throws RemoteException {

books = new Hashtable(100);

}

public BookID getBook(UserID u, String title)

throws RemoteException {

System.out.println("REQUEST TO GET BOOK " + title);

if(books.containsKey(title)) {

Book b = (Book)books.get(title);

System.out.println("getBook: Found it:" + b);

if (b != null) {

if (b.get_borrower() == null) {

b.set_borrower(u);

return b.get_bid();

}

}

}

return null;

}

public PostScript getBookPS(BookID bid)

throws RemoteException {

if (books.containsKey(bid.get_title())) {

Book b = (Book)books.get(bid.get_title());

if (b != null)

return b.get_ps();

}

return null;

}

}

interface PrinterInterface extends Remote {

public boolean print (UserID u, BookID b) throws RemoteException;

}

class Printer extends UnicastRemoteObject

implements PrinterInterface {

String status = “Idle”;

Vector jobs;

private Library theLibrary;

public Printer() throws RemoteException{}

public boolean print (UserID u, BookID b) throws RemoteException{

PostScript ps=null;

try{ps = theLibrary.getBookPS(b);}

catch (RemoteException e) {}

Job newJob = new Job (ps, u.get_name());

return queue(newJob);

}

boolean queue(Job j) {

//...

return true;

}

}

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