uk.ac.sheffield.vtts.client.pojo

Class ShoppingCart

java.lang.Object

uk.ac.sheffield.vtts.client.pojo.ShoppingCart

public class ShoppingCart
extends java.lang.Object

ShoppingCart is a correct POJO implementation of the ShoppingCart.xml specification. This uses the State Pattern (a Design Pattern from Gamma, et al.) for its implementation. All requests are delegated to an abstract State, which has concrete subclasses Ready, Shopping, Checkout and Payment, which respond to certain requests and ignore others. This is a good implementation strategy to ensure that no information is returned by a service, when it is in an inappropriate state.

Otherwise, the shopping cart and the current stock are stored in Maps. As items are added to the cart, they are subtracted from the stock and the total cost of purchases is recalculated. Once there are items in the cart it is possible to go to the checkout. At the checkout, if valid billing information is supplied, payment can be initiated. This must be confirmed for the payment to go through. At any previous step, the user may exit the shop with no obligation. This example uses a user-defined symbolic type, called Dvd, to model the products sold in the shop.

Suggestions are given for how to modify the source code to seed faults deliberately, which will be detected during testing.

Version:

1.0

Author:

Anthony J H Simons

Constructor Summary

Constructors

Constructor and Description
ShoppingCart() Creates this ShoppingCart.

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.Integer	addItem(Dvd dvd) In the Shopping state, adds one Dvd purchase to the cart, if enough stock exists.
java.lang.Boolean	checkout() Attempts to checkout from the Shopping state.
void	clearItems() In the Shopping state, removes all Dvd purchases from the cart.
java.lang.Float	confirm() In the Payment state, confirms the payment and shipping address that were previously supplied and makes the payment.
void	enterShop() Enters the Shopping state from either the Ready state (to start shopping) or from the Checkout state (to return to shopping for extra items before finally making payment).
void	exitShop() Exits the shop from every state, cancelling every action made so far.
java.lang.Float	getBill() In the Checkout or Payment states, enacts getBill/ok and returns the total cost of items in the cart.
java.lang.String	getScenario() Returns the last scenario that was enacted.
java.lang.String	getState() Returns the last state that was entered.
java.lang.Boolean	payBill(int billingInfo, java.lang.String addressInfo) In the Checkout state, attempts to pay the bill.
java.lang.Integer	removeItem(Dvd dvd) In the Shopping state, removes one Dvd purchase from the cart, if a copy exists in the cart.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ShoppingCart

public ShoppingCart()

Creates this ShoppingCart. Enacts the scenario create/ok. Sets the shopping cart to empty, the stock to its initial level, and the total cost to zero. For POJO implementations, the constructor is also used to reset the service.

Method Detail

getScenario

public java.lang.String getScenario()

Returns the last scenario that was enacted. This State Pattern implementation logs separately the request received and the response triggered (which is state-dependent). The name of the last scenario that was enacted is obtained by concatenating the request, "/" and the response.

Returns:

the last scenario that was enacted.

getState

public java.lang.String getState()

Returns the last state that was entered. This State Pattern implementation models the states explicitly as nested inner classes, which also have access to the Account's fields. The name of the current state is obtained by reflection on the class name.

Returns:

the name of the current State instance.

enterShop

public void enterShop()

Enters the Shopping state from either the Ready state (to start shopping) or from the Checkout state (to return to shopping for extra items before finally making payment). Enacts enterShop/ok if in a suitable state; otherwise enacts enterShop/ignore.

exitShop

public void exitShop()

Exits the shop from every state, cancelling every action made so far. Always enacts exitShop/ok.

addItem

public java.lang.Integer addItem(Dvd dvd)

In the Shopping state, adds one Dvd purchase to the cart, if enough stock exists. If there are copies, enacts addItem/ok and adds the Dvd to the cart, removing it from the current stock, and adds the cost of the Dvd to the total cost. Otherwise, enacts addItem/error, since there are no copies. In other states, enacts addItem/ignore.

Parameters:

dvd - the Dvd to add to the cart.

Returns:

the quantity of this Dvd in the cart.

removeItem

public java.lang.Integer removeItem(Dvd dvd)

In the Shopping state, removes one Dvd purchase from the cart, if a copy exists in the cart. If there are copies, enacts removeItem/ok and removes the Dvd from the cart, restoring it to the current stock, and subtracts the cost of the Dvd from the total cost. Otherwise, enacts removeItem/error, since there are no copies. In other states, enacts removeItem/ignore.

Parameters:

dvd - the Dvd to take out of the cart.

Returns:

the quantity of this Dvd in the cart.

clearItems

public void clearItems()

In the Shopping state, removes all Dvd purchases from the cart. Sets the shopping cart to empty, and the stock to its original levels, and the total cost to zero. Enacts clearItems/ok in this state, but clearItems/ignore in all other states.

checkout

public java.lang.Boolean checkout()

Attempts to checkout from the Shopping state. If there are items in the cart, changes state to Checkout and returns true. Otherwise, the state is unchanged and false is returned.

Returns:

true, if checkout succeeded.

getBill

public java.lang.Float getBill()

In the Checkout or Payment states, enacts getBill/ok and returns the total cost of items in the cart. In other states, enacts getBill/ignore.

Returns:

the total amount due, or null if ignored.

payBill

public java.lang.Boolean payBill(int billingInfo,
                        java.lang.String addressInfo)

In the Checkout state, attempts to pay the bill. If correct billing information is provided, enacts payBill/ok, returns true and changes to the Payment state; otherwise enacts payBill/error, returns false and remains in the Checkout state. In other states, enacts payBill/ignore.

Parameters:

billingInfo - an Integer payment authorisation.

addressInfo - the shipping address.

Returns:

true, if valid billing information was given.

confirm

public java.lang.Float confirm()

In the Payment state, confirms the payment and shipping address that were previously supplied and makes the payment. Enacts confirm/ok and returns the amount that was paid. Resets the service and enters the Ready state. In all other states, enacts confirm/ignore.

Returns:

the amount paid, or null.