Java Patterns GDG

Charla para GDG

Transcript

1. Samstag, 24. November 12
   

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2. What is a
   design pattern
   The solution of a coding problem
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3. What is a
   design pattern
   (extended)
   Language independent strategies
   OO Oriented
   Generally a reusable solution
   Not a final solution (template)
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4. More...
   At least 250 types1
   Relationship between them
   -Exclusive
   1The Design Patterns, Java Companion -- by James W. Cooper
   -Natural fitting
   -Leading
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5. Types
   Creational patterns
   1The Design Patterns, Java Companion -- by James W. Cooper
   Creational patterns
   Behavioral patterns
   J2EE patterns
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6. Creational:
   Singleton
   One instance of a class or one value accessible
   globally in an application.
   -Ensure unique instance
   -Access instance controlled way
   -Define a value shared by all system
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7. Creational:
   Singleton
   final class RemoteConnection {
   private Connect con;
   private static RemoteConnection rc = new
   RemoteConnection(connection);
   private RemoteConnection(Connect c) {
   con = c;
   ....
   }
   public static RemoteConnection getRemoteConnection() {
   return rc;
   }
   public void setConnection(Connect c) {
   this(c);
   }
   }
   RemoteConnection rconn = RemoteConnection.getRemoteConnection;
   rconn.loadData();
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8. Creational:
   Prototype
   Cloning an object by reducing the cost of
   creation.
   -Many subclasses, only differ object type
   -Add/remove objects and runtime
   -Configure an application dynamically
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9. Creational:
   Prototype
   interface Shape {
   public void draw();
   }
   class Line implements Shape {
   public void draw() {
   System.out.println("line");
   }
   }
   class Square implements Shape {
   public void draw() {
   System.out.println("square");
   }
   }
   class Circle implements Shape {
   public void draw() {
   System.out.println("circle");
   }
   }
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10. Creational:
    Prototype
    class Painting {
    public static void main(String[]
    args) {
    Shape s1 = new Line();
    Shape s2 = new Square();
    Shape s3 = new Circle();
    paint(s1);
    paint(s2);
    paint(s3);
    }
    static void paint(Shape s) {
    s.draw();
    }
    }
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11. Structural:
    Adapter
    Convert existing interfaces to a new interface
    to achieve compatibility and reusability. Also
    known as Wrapper pattern.
    Related: Proxy, Decorator or Bridge
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12. Structural:
    Adapter
    public interface Windowlistener {
    public void windowClosed(WindowEvent e);
    public void windowOpened(WindowEvent e);
    public void windowIconified(WindowEvent e);
    public void windowDeiconified(WindowEvent e);
    public void windowActivated(WindowEvent e);
    public void windowDeactivated(WindowEvent e);
    public void windowClosing(WindowEvent e);
    }
    public class WindowAdapter implements WindowListner{
    public void windowClosed(WindowEvent e){}
    public void windowOpened(WindowEvent e){}
    public void windowIconified(WindowEvent e){}
    public void windowDeiconified(WindowEvent e){}
    public void windowActivated(WindowEvent e){}
    public void windowDeactivated(WindowEvent e){}
    public void windowClosing(WindowEvent e){}
    }
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13. Structural:
    Adapter
    import javax.swing.*;
    import java.awt.event.*;
    class Test extends JFrame {
    public Test () {
    setSize(200,200);
    setVisible(true);
    addWindowListener(new Closer());
    }
    public static void main(String[] args) {
    new Test();
    }
    class Closer extends WindowAdapter {
    public void windowClosing(WindowEvent e) {
    System.exit(0);
    }
    }
    }
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14. Structural:
    Façade
    Make a complex system simpler by providing a
    unified or general interface.
    -Make an entry point to your subsystems.
    -Minimize communication and independency
    -Security and performance considerations
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15. Structural:
    Façade
    interface General {
    public void accessGeneral();
    }
    interface Special extends General {
    public void accessSpecial();
    }
    interface Private extends General {
    public void accessPrivate();
    }
    class GeneralInfo implements General {
    public void accessGeneral() {
    ! //...
    }
    //...
    }
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16. Structural:
    Façade
    class SpecialInfo implements Special{
    public void accessSpecial() {
    //...
    }
    public void accessGeneral() {}
    //...
    }
    class PrivateInfo implements Private, Special {
    public void accessPrivate() {
    ! // ...
    }
    public void accessSpecial() {
    ! //...
    }
    public void accessGeneral() {
    ! // ...
    }
    //...
    }
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17. Structural:
    Façade
    class Connection {
    //...
    if (user is unauthorized) throw new Exception();
    if (user is general) return new GeneralInfo();
    if (user is special) return new SpecialInfo();
    if (user is executive) return new PrivateInfo();
    //...
    }
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18. Behavioral:
    Memento
    Record states
    -Need undo/redo features.
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19. Behavioral:
    Memento
    class Memento {
    int num;
    Memento(int c) {
    num = c;
    }
    int getNum() {
    return num;
    }
    }
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20. Behavioral:
    Memento
    class BtnDice extends JButton implements Command {
    Mediator med;
    BtnDice(ActionListener al, Mediator m) {
    super("Throw Dice");
    addActionListener(al);
    med = m;
    med.registerDice(this);
    }
    public void execute() {
    med.throwit();
    }
    }
    class BtnClear extends JButton implements Command {
    Mediator med;
    BtnClear(ActionListener al, Mediator m) {
    super("Clear");
    addActionListener(al);
    med = m;
    med.registerClear(this);
    }
    public void execute() {
    med.clear();
    }
    }
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21. Behavioral:
    Memento
    class BtnPrevious extends JButton implements Command {
    Mediator med;
    BtnPrevious(ActionListener al, Mediator m) {
    super("Previous");
    addActionListener(al);
    med = m;
    med.registerPrevious(this);
    }
    public void execute() {
    med.previous();
    }
    }
    class LblDisplay extends JLabel{
    Mediator med;
    LblDisplay (Mediator m) {
    super("0",JLabel.CENTER);
    med = m;
    med.registerDisplay(this);
    setBackground(Color.white);
    setBorder(new EtchedBorder(Color.blue, Color.green));
    Font font = new Font("Arial",Font.BOLD,40);
    setFont(font);
    }
    }
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22. Behavioral:
    Memento
    Class Mediator {
    BtnDice btnDice;
    BtnPrevious btnPrevious;
    BtnClear btnClear;
    LblDisplay show;
    java.util.List list, undo;
    boolean restart = true;
    int counter = 0, ct = 0;
    //....
    Mediator() {
    list = new ArrayList();
    undo = new ArrayList();
    }
    void registerDice(BtnDice d) {
    btnDice = d;
    }
    void registerClear(BtnClear c) {
    btnClear = c;
    }
    void registerPrevious(BtnPrevious p) {
    btnPrevious = p;
    }
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23. Behavioral:
    Memento
    void registerDisplay(LblDisplay d) {
    show = d;
    }
    void throwit() {
    show.setForeground(Color.black);
    int num = (int)(Math.random()*6 +1);
    int i = counter++;
    list.add(i, new Integer(num));
    undo.add(i, new Memento(num));
    show.setText(""+num);
    }
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24. Behavioral:
    Memento
    void previous() {
    show.setForeground(Color.red);
    btnDice.setEnabled(false);
    if (undo.size() > 0) {
    ct = undo.size()-1;
    Memento num = (Memento)undo.get(ct);
    show.setText(""+num.getNum());
    undo.remove(ct);
    }
    if (undo.size() == 0)
    show.setText("0");
    }
    void clear() {
    list = new ArrayList();
    undo = new ArrayList();
    counter = 0;
    show.setText("0");
    btnDice.setEnabled(true);
    }
    }
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25. Behavioral:
    Memento
    class MementoDemo extends JFrame implements
    ActionListener {
    Mediator med = new Mediator();
    MementoDemo() {
    JPanel p = new JPanel();
    p.add(new BtnDice(this,med));
    p.add(new BtnPrevious(this,med));
    p.add(new BtnClear(this,med));
    JPanel dice = new JPanel();
    LblDisplay lbl = new LblDisplay(med);
    dice.add(lbl);
    getContentPane().add(dice, "Center");
    getContentPane().add(p, "South");
    setTitle("Memento pattern example");
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setSize(400,200);
    setVisible(true);
    }
    public void actionPerformed(ActionEvent ae) {
    Command comd = (Command)ae.getSource();
    comd.execute();
    }
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26. Behavioral:
    Memento
    public static void main(String[] args) {
    new MementoDemo();
    }
    }
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27. Behavioral:
    Observer
    One object changes state, all of its dependents
    are updated automatically.
    -Publish or subscription
    -Broadcast communication
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28. Behavioral:
    Observer
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29. Behavioral:
    Observer
    public class EventSource extends Observable implements Runnable
    {
    public void run() {
    try {
    final InputStreamReader isr = new
    InputStreamReader(System.in);
    final BufferedReader br = new BufferedReader(isr);
    while (true) {
    String response = br.readLine();
    setChanged();
    notifyObservers(response);
    }
    }
    catch (IOException e) {
    e.printStackTrace();
    }
    }
    }
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30. Behavioral:
    Observer
    public class ResponseHandler implements Observer {
    private String resp;
    public void update(Observable obj, Object arg) {
    if (arg instanceof String) {
    resp = (String) arg;
    System.out.println("\nReceived Response: " + resp );
    }
    }
    }
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31. Behavioral:
    Observer
    public class MyApp {
    public static void main(String[] args) {
    System.out.println("Enter Text >");
    // create an event source - reads from stdin
    final EventSource eventSource = new EventSource();
    // create an observer
    final ResponseHandler responseHandler = new
    ResponseHandler();
    // subscribe the observer to the event source
    eventSource.addObserver(responseHandler);
    // starts the event thread
    Thread thread = new Thread(eventSource);
    thread.start();
    }
    }
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32. Java MVC
    -MVC
    -Business Delegate
    -Data Access Object
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33. The design patterns may just be a sign of some
    missing features of a given programming
    language (Java or C++ for instance).
    Peter Norvig demonstrates that 16 out of the
    23 patterns in the Design Patterns book (that is
    primarily focused on C++) are simplified or
    eliminated (via direct language support) in Lisp..
    Moreover, inappropriate use of patterns may
    unnecessarily increase complexity
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34. Books:
    -Clean Code (Clean Code: A Handbook of Agile Software
    Craftsmanship (Robert C. Martin))
    -The Design Patterns, Java Companion (James W. Cooper)
    Websites:
    http://www.oracle.com/technetwork/java/index.html
    http://c2.com/cgi/wiki?PeopleProjectsAndPatterns
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35. Thank you !
    + http://goo.gl/t4AVh
    @eenriquelopez
    http://www.neo-tech.es
    Samstag, 24. November 12
    

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