CS 415 N-Tier Application Development

1. National University of Computer and Emerging Sciences Lecture # 4 Web Presentation Patterns (MVC, Page Controller, Front Controller) CS 415 N-Tier Application Development By Umair Ashraf June 25 ,2013

2. Contents • MVC (Model, View Controller) Pattern Web Presentation Patterns: • MVC (Model, View Controller) Pattern • Page Controller Pattern • Front Page Controller Pattern Practical Demonstration

22. public interface BeatModelInterface { void initialize(); void on(); void off(); void setBPM(intbpm); intgetBPM(); void registerObserver(BeatObserver o); void removeObserver(BeatObserver o); void registerObserver(BPMObserver o); void removeObserver(BPMObserver o); }

23. public class BeatModel implements BeatModelInterface, MetaEventListener { • Sequencer sequencer; • ArrayListbeatObservers = new ArrayList(); • ArrayListbpmObservers = new ArrayList(); • intbpm = 90; • //other instance variables here • public void initialize() { • setUpMidi(); • buildTrackAndStart(); • } • public void on() { • sequencer.start(); • setBPM(90); • } • public void off() { • setBPM(0); • sequencer.stop(); • }

24. public void setBPM(intbpm) { this.bpm = bpm; sequencer.setTempoInBPM(getBPM()); notifyBPMObservers(); } public intgetBPM() { return bpm; } void beatEvent() { notifyBeatObservers(); } //code to register and notify observers //Lots of MIDI code to handle the beat }

27. public class DJView implements ActionListener, BeatObserver, BPMObserver { BeatModelInterface model; ControllerInterface controller; JFrameviewFrame; JPanelviewPanel; BeatBarbeatBar; JLabelbpmOutputLabel; public DJView(ControllerInterface controller, BeatModelInterface model) { this.controller = controller; this.model = model; model.registerObserver((BeatObserver)this); model.registerObserver((BPMObserver)this); } public void createView() { //Create all Swing components here }

28. public void updateBPM() { intbpm = model.getBPM(); if (bpm == 0) { bpmOutputLabel.setText("offline"); } else { bpmOutputLabel.setText("Current BPM: " + model.getBPM()); } } public void updateBeat() { beatBar.setValue(100); } }

29. public class DJView implements ActionListener, BeatObserver, BPMObserver { BeatModelInterface model; ControllerInterface controller; JLabelbpmLabel; JTextFieldbpmTextField; JButtonsetBPMButton; JButtonincreaseBPMButton; JButtondecreaseBPMButton; JMenuBarmenuBar; JMenu menu; JMenuItemstartMenuItem; JMenuItemstopMenuItem; public void createControls() { //Create all Swing components here }

30. public void enableStopMenuItem() { stopMenuItem.setEnabled(true); } public void disableStopMenuItem() { stopMenuItem.setEnabled(false); } public void enableStartMenuItem() { startMenuItem.setEnabled(true); } public void disableStartMenuItem() { startMenuItem.setEnabled(false); } public void actionPerformed(ActionEvent event) { if (event.getSource() == setBPMButton) { intbpm = Integer.parseInt(bpmTextField.getText()); controller.setBPM(bpm); } else if (event.getSource() == increaseBPMButton) { controller.increaseBPM(); } else if (event.getSource() == decreaseBPMButton) { controller.decreaseBPM(); } } }

31. public interface ControllerInterface { void start(); void stop(); void increaseBPM(); void decreaseBPM(); void setBPM(intbpm); }

33. public class BeatController implements ControllerInterface { BeatModelInterface model; DJView view; public BeatController(BeatModelInterface model) { this.model = model; view = new DJView(this, model); view.createView(); view.createControls(); view.disableStopMenuItem(); view.enableStartMenuItem(); model.initialize(); } public void start() { model.on(); view.disableStartMenuItem(); view.enableStopMenuItem(); }

34. public void stop() { model.off(); view.disableStopMenuItem(); view.enableStartMenuItem(); } public void increaseBPM() { intbpm = model.getBPM(); model.setBPM(bpm + 1); } public void decreaseBPM() { intbpm = model.getBPM(); model.setBPM(bpm - 1); } public void setBPM(intbpm) { model.setBPM(bpm); } }

35. public class DJTestDrive { public static void main (String[] args) { BeatModelInterface model = new BeatModel(); ControllerInterface controller = new BeatController(model); } }

37. LUDO Game in MVC

38. MVC implementation in ASP.NET Practical Demonstration

39. Page Controller Pattern Use the Page Controller pattern to accept input from the page request, invoke the requested actions on the model, and determine the correct view to use for the resulting page

40. Page Controller Pattern

41. Page Controller in ASP.NET

42. Front Page Controller Pattern Front Controller solves the decentralization problem present in Page Controller by channeling all requests through a single controller. The controller itself is usually implemented in two parts: a handler and a hierarchy of commands 

43. Reference Material Text Book :Head First Design Patterns by GOF (EBook uploaded on website ) Web Presentation Patterns : http://msdn.microsoft.com/en-us/library/ff650511.aspx