session.java

来自「含有uml的多个实例及实例的java源码。」· Java 代码 · 共 163 行

/*
 * ATM Example system - file Session.java
 *
 * copyright (c) 2001 - Russell C. Bjork
 *
 */
 
package atm;
import banking.Card;
import banking.Status;
import banking.Receipt;
import atm.physical.CustomerConsole;
import atm.transaction.Transaction;

/** Representation for one ATM session serving a single customer. */

public class Session
{
    /** Constructor
     *
     *  @param atm the ATM on which the session is performed
     */
    public Session(ATM atm)
    {
        this.atm = atm;
        
        state = READING_CARD_STATE;
    }

    /** Perform the Session Use Case
     */
    public void performSession()
    {
        Card card = null;
        Transaction currentTransaction = null;
        
        while (state != FINAL_STATE)
        {
            switch(state)
            {
                case READING_CARD_STATE:
                
                
                    card = atm.getCardReader().readCard();
                    
                    if (card != null)
                        state = READING_PIN_STATE;
                    else
                    {
                        atm.getCustomerConsole().display("Unable to read card");
                        state = EJECTING_CARD_STATE;
                    }
                    break;
                    
                case READING_PIN_STATE:
                
                    try
                    {
                        pin = atm.getCustomerConsole().readPIN(
                            "Please enter your PIN\n" +
                            "Then press ENTER");
                        state = CHOOSING_TRANSACTION_STATE;
                    }
                    catch(CustomerConsole.Cancelled e)
                    {
                        state = EJECTING_CARD_STATE;
                    }
                    break;
                
                case CHOOSING_TRANSACTION_STATE:
                
                    try
                    {
                        currentTransaction = 
                            Transaction.makeTransaction(atm, this, card, pin);
                        state = PERFORMING_TRANSACTION_STATE;
                    }
                    catch(CustomerConsole.Cancelled e)
                    {
                        state = EJECTING_CARD_STATE;
                    }
                    break;
                    
                case PERFORMING_TRANSACTION_STATE:
                
                    try
                    {
                        boolean doAgain = 
                            currentTransaction.performTransaction();
                        if (doAgain)
                            state = CHOOSING_TRANSACTION_STATE;
                        else
                            state = EJECTING_CARD_STATE;
                    }
                    catch(Transaction.CardRetained e)
                    {
                        state = FINAL_STATE;
                    }
                    break;
                    
                case EJECTING_CARD_STATE:
                
                    atm.getCardReader().ejectCard();
                    state = FINAL_STATE;
                    break;
            }
        }
    }
    
    /** Change the pin recorded for the customer (if invalid pin extension
     *  was performed by a transaction
     *
     *  @param pin the newly entered pin
     */
    public void setPIN(int pin)
    {
        this.pin = pin;
    }
    

    // Instance variables


    /** The ATM on which the session is performed
     */
    private ATM atm;
    
    /** The PIN entered (or re-entered) by the customer
     */
    private int pin;

    /** The current state of the session
     */
    private int state;
    
    // Possible values for state
    
    /** Reading the customer's card
     */
    private static final int READING_CARD_STATE = 1;
    
    /** Asking the customer to enter a PIN
     */
    private static final int READING_PIN_STATE = 2;
    
    /** Asking the customer to choose a transaction type
     */
    private static final int CHOOSING_TRANSACTION_STATE = 3;
    
    /** Peforming a transaction
     */
    private static final int PERFORMING_TRANSACTION_STATE = 4;
    
    /** Ejecting the customer's card
     */
    private static final int EJECTING_CARD_STATE = 5;
    
    /** Session finished
     */
    private static final int FINAL_STATE = 6;
    
}