/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
package je3.rmi;
import java.rmi.*;
import java.rmi.server.*;
import java.util.*;
import je3.rmi.Bank.*;
/**
* This class implements the remote methods defined by the RemoteBank
* interface. It has a serious shortcoming, though: all account data is
* lost when the server goes down.
**/
public class RemoteBankServer extends UnicastRemoteObject implements RemoteBank
{
/**
* This nested class stores data for a single account with the bank
**/
class Account {
String password; // account password
int balance; // account balance
List transactions = new ArrayList(); // account transaction history
Account(String password) {
this.password = password;
transactions.add("Account opened at " + new Date());
}
}
/**
* This hashtable stores all open accounts and maps from account name
* to Account object. Methods that use this object will be synchronized
* to prevent concurrent access by more than one thread.
**/
Map accounts = new HashMap();
/**
* This constructor doesn't do anything, but because the superclass
* constructor throws an exception, the exception must be declared here
**/
public RemoteBankServer() throws RemoteException { super(); }
/**
* Open a bank account with the specified name and password
* This method is synchronized to make it thread safe, since it
* manipulates the accounts hashtable.
**/
public synchronized void openAccount(String name, String password)
throws RemoteException, BankingException
{
// Check if there is already an account under that name
if (accounts.get(name) != null)
throw new BankingException("Account already exists.");
// Otherwise, it doesn't exist, so create it.
Account acct = new Account(password);
// And register it
accounts.put(name, acct);
}
/**
* This internal method is not a remote method. Given a name and password
* it checks to see if an account with that name and password exists. If
* so, it returns the Account object. Otherwise, it throws an exception.
* This method is synchronized because it uses the accounts hashtable.
**/
synchronized Account verify(String name, String password)
throws BankingException
{
Account acct = (Account)accounts.get(name);
if (acct == null) throw new BankingException("No such account");
if (!password.equals(acct.password))
throw new BankingException("Invalid password");
return acct;
}
/**
* Close the named account. This method is synchronized to make it
* thread safe, since it manipulates the accounts hashtable.
**/
public synchronized FunnyMoney closeAccount(String name, String password)
throws RemoteException, BankingException
{
Account acct;
acct = verify(name, password);
accounts.remove(name);
// Before changing the balance or transactions of any account, we first
// have to obtain a lock on that account to be thread safe.
synchronized (acct) {
int balance = acct.balance;
acct.balance = 0;
return new FunnyMoney(balance);
}
}
/** Deposit the specified FunnyMoney to the named account */
public void deposit(String name, String password, FunnyMoney money)
throws RemoteException, BankingException
{
Account acct = verify(name, password);
synchronized(acct) {
acct.balance += money.amount;
acct.transactions.add("Deposited " + money.amount +
" on " + new Date());
}
}
/** Withdraw the specified amount from the named account */
public FunnyMoney withdraw(String name, String password, int amount)
throws RemoteException, BankingException
{
Account acct = verify(name, password);
synchronized(acct) {
if (acct.balance < amount)
throw new BankingException("Insufficient Funds");
acct.balance -= amount;
acct.transactions.add("Withdrew " + amount + " on "+new Date());
return new FunnyMoney(amount);
}
}
/** Return the current balance in the named account */
public int getBalance(String name, String password)
throws RemoteException, BankingException
{
Account acct = verify(name, password);
synchronized(acct) { return acct.balance; }
}
/**
* Return a Vector of strings containing the transaction history
* for the named account
**/
public List getTransactionHistory(String name, String password)
throws RemoteException, BankingException
{
Account acct = verify(name, password);
synchronized(acct) { return acct.transactions; }
}
/**
* The main program that runs this RemoteBankServer.
* Create a RemoteBankServer object and give it a name in the registry.
* Read a system property to determine the name, but use "FirstRemote"
* as the default name. This is all that is necessary to set up the
* service. RMI takes care of the rest.
**/
public static void main(String[] args) {
try {
// Create a bank server object
RemoteBankServer bank = new RemoteBankServer();
// Figure out what to name it
String name = System.getProperty("bankname", "FirstRemote");
// Name it that
Naming.rebind(name, bank);
// Tell the world we're up and running
System.out.println(name + " is open and ready for customers.");
}
catch (Exception e) {
System.err.println(e);
System.err.println("Usage: java [-Dbankname=<name>] " +
"je3.rmi.RemoteBankServer");
System.exit(1); // Force exit because there may be RMI threads
}
}
}
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