Abstract Factory Pattern (Creational Pattern) Week 05 (2nd Half) Report 05 A. Firuza Aibara P11119

Transcription

1 Abstract Factory Pattern (Creational Pattern) Week 05 (2nd Half) Report 05 A By Firuza Aibara P August 2012

2 Contents 1 Abstract Factory Design Pattern Introduction Interface/Base Class Attribute Class Concrete Factory Classes Abstract Driver Program Initialization/Definition Constructor Creating User Interface Item Listeners Action Listeners Executing Methods for Action Display Area Conclusion

3 Chapter 1 Abstract Factory Design Pattern 1.1 Introduction An abstract factory is a factory object that returns one of several group of classes. [1, p. 33]. It is used to return any object of a class which in turn can return different objects. An example would be a DocumentCreator class that provides the interfaces to create different ytpe of documents like letters, reports, resume, thesis, etc.. Consider another example of a program to get attributes of various devices like monitor, keyboard, mouse, printer, etc.. Each of the devices include basic specification like size, color, and type. More attributes/specifications can be added later. Irrespective of any devices, these are some common specification required. calls comp.getcolor(). getattribute() Attribute Attribute() getdevicename():string <<Computer>> gettype():attribute getcolor():attribute getsize():attribute Configuration Configuration() setgui() settype() setcolor() setsize() clearcanvas() main() Monitor gettype() getcolor() getsize() Mouse gettype() getcolor() getsize() Speaker gettype() getcolor() getsize() Returns instance of Attribute(Name) Fig1: Abstract Factory Class Diagram 2

4 1.2 Interface/Base Class The interface/base class defines the methods of the concrete factory classes. interface Computer public Attribute gettype(); public Attribute getcolor(); public Attribute getsize(); 1.3 Attribute Class The methods gettype(), getcolor(), and getsize(), defined in the interface, have return type of Attribute class. This class only returns the value of the attribute of a particular computer device, which is invoked by the concrete factory classes. class Attribute private String name; public Attribute(String pname) name = pname; public String getattribute() return name; 1.4 Concrete Factory Classes The concrete factory classes are the subclasses that return the instance of the class with a particlar value of the attribute. For example the size of the monitor returned would be 19 inches. Thus, the method will return the information of that particular category of that class. class Monitor implements Computer public Attribute gettype() return new Attribute("LED Monitor"); public Attribute getcolor() return new Attribute("Black"); 25 August 2012 Week 05B Report 05A 3

5 public Attribute getsize() return new Attribute("26 inches"); Similarly, such concrete factory classes can be written. class Speaker implements Computer public Attribute gettype() return new Attribute("Satellite Speaker"); public Attribute getcolor() return new Attribute("Pink"); public Attribute getsize() return new Attribute("Big"); class Mouse implements Computer public Attribute gettype() return new Attribute("Bluetooth Mouse"); public Attribute getcolor() return new Attribute("Silver"); public Attribute getsize() return new Attribute("Mini"); 25 August 2012 Week 05B Report 05A 4

6 1.5 Abstract Driver Program This program(configuration.java) contains the GUI, listeners, and returns one of the computer objects based on the radio button selected and button clicked by the user. Fig 2: GUI of Program(configuration.java) The program uses Frame concept of Java, that supports GUI components like radio buttons, checkboxes, command buttons, area for displaying and writing, etc.. Different components respond according to the events/actions which are monitored by Listeners, in a program. For example, keylisteners will monitor if any key is pressed on the keyboard and will execute the task associated with it. This program contains 3 radio buttons that specifies the type of devices, and 3 command buttons that specifies the common attributes of any device. There is one more command button to exit the program. Any action associated with the radio button invokes ItemListener and creates object of that concrete factory class. Any action associated with the command button invokes ActionListener, which calls appropriate methods of that concrete class. The concrete class, in turn returns the instance of the Attribute class. public class configuration extends Frame implements ActionListener August 2012 Week 05B Report 05A 5

7 1.5.1 Initialization/Definition This part of the program contains the declaration of variables, various checkboxes and command buttons to be added, and the panel for displaying text. private Checkbox monitor, speaker, mouse; private Button Type, Color, Size, Quit; private Computer comp = null; private ComputerPanel cp; private String sizedevice = "", colordevice = "", typedevice = ""; Constructor The constructor sets the title of the frame Abstract Factory Pattern and calls the setgui() method for creating the user interface. public configuration() super("abstract Factory Pattern"); setgui(); 25 August 2012 Week 05B Report 05A 6

8 1.5.3 Creating User Interface The user interface is created using frames. Two panels are created which divides the screen into left and right. The left panel is again divided into seven parts that comprise of radiobuttons and command buttons. These are added on the left panel. ItemListener is set for every radiobutton and ActionListener is set for every command button present on the panel. This is required to execute the ItemListener and ActionListener methods. The right panel is used for displaying text. It can be considered as a canvas used for painting and drawing. private void setgui() //Divide screen into two columns "left and right(panels)" setlayout(new GridLayout(1, 2)); Panel left = new Panel(); add(left); Panel right = new Panel(); add(right); //Divide left panel into seven rows left.setlayout(new GridLayout(7, 1)); CheckboxGroup grp = new CheckboxGroup(); //add check box to panel and create ItemListener for each monitor = new Checkbox("Monitor", grp, false); speaker = new Checkbox("Speaker", grp, false); mouse = new Checkbox("Mouse", grp, false); left.add(monitor); left.add(speaker); left.add(mouse); monitor.additemlistener(new MonitorListener()); mouse.additemlistener(new MouseListener()); speaker.additemlistener(new SpeakerListener()); //add command button to panel and create ActionListener for each Type = new Button("Type"); Color = new Button("Color"); Size = new Button("Size"); Quit = new Button("Quit"); left.add(type); left.add(color); left.add(size); left.add(quit); Type.addActionListener(this); Color.addActionListener(this); Size.addActionListener(this); Quit.addActionListener(this); 25 August 2012 Week 05B Report 05A 7

9 //Add drawing panel on the right right.setlayout(new GridLayout(1, 1)); cp = new ComputerPanel(); right.add(cp); //Set the positon of the window setbounds(200, 200, 400, 300); setvisible(true); 25 August 2012 Week 05B Report 05A 8

10 1.5.4 Item Listeners ItemListener are created for every radiobutton present on the panel. An event occurs whenever the radio button is clicked, which invokes itemstatechanged() method of ItemListener. Here, an object is created for that concrete factory class. class MonitorListener implements ItemListener public void itemstatechanged(itemevent e) comp = new Monitor(); clearcanvas(); class MouseListener implements ItemListener public void itemstatechanged(itemevent e) comp = new Mouse(); clearcanvas(); class SpeakerListener implements ItemListener public void itemstatechanged(itemevent e) comp = new Speaker(); clearcanvas(); private void clearcanvas() typedevice = ""; colordevice = ""; sizedevice = ""; cp.repaint(); clearcanvas() is used to reset the value of the variables and to repaint/clear the drawing/display area. cp.repaint() method is used to clear the display area(canvas), and to load the area with new/current values. 25 August 2012 Week 05B Report 05A 9

11 1.5.5 Action Listeners A command button when clicked, invokes the actionperformed() method. It checks the command button that invoked the function and then calls respective methods. public void actionperformed(actionevent e) Object obj = e.getsource(); if (obj == Type) settype(); if (obj == Color) setcolor(); if (obj == Size) setsize(); if (obj == Quit) System.exit(0); 25 August 2012 Week 05B Report 05A 10

12 1.5.6 Executing Methods for Action Every command button has some task to be performed. It invokes the appropriate concrete class methods of a particular attribute. private void setcolor() if (comp!= null) colordevice = comp.getcolor().getattribute(); cp.repaint(); private void setsize() if (comp!= null) sizedevice = comp.getsize().getattribute(); cp.repaint(); private void settype() if (comp!= null) typedevice = comp.gettype().getattribute(); cp.repaint(); cp.repaint() method is used to clear the display area(canvas), and to load the area with new/current values. 25 August 2012 Week 05B Report 05A 11

13 1.5.7 Display Area ComputerPanel is placed added to the right panel. This calls the panint() method that is used to draw, and write text using different graphic methods. class ComputerPanel extends Panel public void paint(graphics g) Dimension sz = getsize(); g.drawrect(0, 0, sz.width - 1, sz.height - 1); g.drawstring("select a device", 50, 20); g.drawstring("click button to view values", 15, 40); g.drawstring(typedevice, 10, 140); g.drawstring(colordevice, 10, 180); g.drawstring(sizedevice, 10, 220); Fig 3: Output of Program(configuration.java) 1.6 Conclusion It is easy to add new subclasses i.e. concrete factory and classes. For example, a new attribute can be added very easily. If abstract factory pattern was not used in this case, separate code would have to be written with every action of the radio button and command button. Moreover, in future, it would create problem, if more classes would have been added. By using this design pattern, only sub class would be added and the appropriate call invoke the method. 25 August 2012 Week 05B Report 05A 12

14 Bibliography [1] James W. Cooper. JAVA TM Design Patterns, A Tutorial. Pearson Education. Nov pp Indian Reprint