OpenCard Framework 1.2 Programmer's Guide - OpenSCDP

Chapter 5. Advanced programming with OCF
In this chapter, we’ll show you some more advanced programming concepts of the
OPENCARD FRAMEWORK.
Working with OpenCard events
OpenCard uses the Observer design pattern to inform listeners about events that
happen in the framework.
In the OPENCARD FRAMEWORK reference implementation, there are a number of
objects that can be the source of OpenCardEvent objects that other framework
components or the application itself might be interested in. The implementation of
the event notification is based on EventObject class and EventListener interface of
the java.util package.
Objects that are interested in receiving event notifications must implement some
extension of the EventListener interface and register with the proper object by
adding themselves as listeners.
As an application programmer, you may be interested in the following types of
OPENCARD FRAMEWORK events:
v events signalling that a card was inserted or removed into a card terminal,
v events signalling that a tracer issued a tracing message.
CardTerminalEvent
In previous versions of OCF the CardTerminalRegistry was responsible to emit
card insertion/removal events. This function is now moved to class
EventGenerator in the events package to have a clearer separation between the
events and terminal package. The EventGenerator continuously monitors the state
of physical card reader devices and emits CardTerminalEvents if the state changes.
The CTListener interface defines two methods, cardInserted() and cardRemoved(),
through which CardTerminalEvents can be communicated to objects interested in
these events.
You can register objects that are interested in receiving CardTerminalEvents
provided they implement the CTListener interface. You can register your
CTListener with the system-wide EventGenerator instance using the addListener()
and removeListener() methods. The registered objects will then receive all
CardTerminalEvents produced by all currently-registered CardTerminal objects.
Locking a CardTerminal
Once you hava a SmartCard object you can gain exclusive access using the
SmartCard.beginMutex() methods. This is described under “Gaining exclusive
access to the smart card” on page 35
There are other scenarios like transferring money from one smartcard to another
one where you need to maintain a lock on an individual slot or the whole
CardTerminal across card insertions and card removals.
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