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CSCI 444 / CIS 644 Event Driven Programming

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CSCI 444 / CIS 644 Event Driven Programming. Outline . What is an event driven system? What is event driven programming? Course Overview. I. What is an event driven system?. An event is an occurrence of interest Events take place at a particular time

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Presentation Transcript
  • What is an event driven system?
  • What is event driven programming?
  • Course Overview
i what is an event driven system
I. What is an event driven system?
  • An event is an occurrence of interest
    • Events take place at a particular time
  • An event driven system is a computer system where events are a driving force
    • Events from the user (mouse click)
    • Internal events (variable assignment, timers)
    • Events from other computing systems (any message arriving across the network)
examples of event driven systems
Examples of Event Driven Systems
  • Vending Machines
  • Cruise Control System in a car
  • TV
  • Any modern windowing program
    • e.g. PowerPoint

What are the events associated with each of these?

ii event driven programming
II. Event Driven Programming
  • Fundamentally a different paradigm from procedural (or OOP or functional or logic) programming
    • System is made of objects
    • System spends much of its time in stasis
    • Events occur that propagate through the system and then it returns to statis
basic event driven programming model
Basic Event Driven Programming Model


Event Source

Event Handler


System Objects

what makes this model unique
What makes this model unique?
  • Loose Coupling between source and handler
    • Runtime registration
    • Multicasting
    • Multiplexing
    • Separate Compilation
    • Inverted Semantics
differences continued
Differences continued
  • State based control
    • Behavior of system depends on its state
    • E.g. Coke machine only delivers pop after enough money has been inserted
    • Good ways and bad ways to implement this
differences continued1
Differences continued
  • Concurrent and Distributed processing
    • If a handler takes too much time, other events might be delayed/lost
    • One solution is to have handler execute is a separate thread.
      • Concurrency concerns now become important.
      • E.g. what happens is multiple events arrive in rapid sequence? Might there be multiple threads executing in the same handler?
concurrent and distributed processing continued
Concurrent and Distributed Processing - continued
  • Distributed Processing
    • Source and Handler might be on different computing systems entirely.
    • E.g. a web browser makes a request for a web page from a server.
    • Client / Server computing is fairly well understood. There are many other models, however.
course outline
Course Outline
  • Java Event Driven Programming
  • Component Based Programming in Java
  • Concurrent and Distributed Event Programming
  • Software Engineering Event Driven Systems