The JavaPurse sample application consists of two components, a JavaPurse applet and a JavaLoyalty applet.
The JavaPurse applet demonstrates a simple electronic cash application. The applet is selected and initialized with various parameters such as the Purse ID, the expiration date of the card, the Master and User PINs, maximum balance, and maximum transaction. Transaction operations perform the actual debits and credits to the electronic purse. If a configured loyalty applet is assigned for the CAD performing the transaction, JavaPurse communicates with it to grant loyalty points. In this sample, JavaLoyalty is the provided loyalty applet.
A number of transaction sessions are simulated where amounts are credited and debited from the card. In an additional session, transactions with intentional errors are attempted to demonstrate the security features of the card.
The JavaLoyalty applet is a minimalistic loyalty applet that interacts with the JavaPurse applet and demonstrates the use of shareable interfaces. The shareable JavaLoyaltyInterface is defined in a separate library package, com.sun.javacard.SampleLibrary.
JavaLoyalty applet is registered with JavaPurse when a Parameter Update APDU command with an appropriate parameter tag is executed, and when the AID part of the parameter corresponds to the AID of the JavaLoyalty applet. The applet contains a grantPoints method. This method implements the main interaction with the client. The grantPoints method implementing the JavaLoyaltyInterface is requested when the first two bytes of the CAD ID in a request by a JavaPurse transaction correspond to the two bytes of CAD ID in the corresponding Parameter Update APDU command.
JavaLoyalty maintains the balance of loyalty points. The JavaLoyalty applet contains methods to credit and debit the account of points and to get and set the balance.