设计模式-中介者模式

Posted on | In
Words count in article: 603 | Reading time ≈ 3

中介者模式

定义

中介者模式（Mediator Pattern）是用来降低多个对象和类之间的通信复杂性。这种模式提供了一个中介类，该类通常处理不同类之间的通信，并支持松耦合，使代码易于维护。

类图

中介者模式类图

Mediator

负责定义了与Colleague角色进行通信和做出决定的接口

ConcreteMediator(具体的仲裁者、中介者)

负责实现Mediator接口，负责实际做出决定。

Colleague（同事）

负责定义与Mediator进行通信的接口

ConcreteColleague（具体的同时）

负责实现Colleague的接口。

示例

类图

中介者模式示例类图

Colleague

1
2
3
4
5
public interface Colleague {
    public abstract void setMediator(Mediator mediator);
    public abstract void setColleagueEnabled(boolean enabled);
}

ColleagueButton

1
2
3
4
5
6
7
8
9
10
11
12
13
public class ColleagueButton extends Button implements Colleague {
    private Mediator mediator;
    public ColleagueButton(String caption) {
        super(caption);
    }
    public void setMediator(Mediator mediator) {            
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {      
        setEnabled(enabled);
    }
}

ColleagueCheckbox

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
public class ColleagueCheckbox extends Checkbox implements ItemListener, Colleague {
    private Mediator mediator;
    public ColleagueCheckbox(String caption, CheckboxGroup group, boolean state) {  
        super(caption, group, state);
    }
    public void setMediator(Mediator mediator) {            
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {      
        setEnabled(enabled);
    }
    public void itemStateChanged(ItemEvent e) {             
        mediator.colleagueChanged();
    }
}

ColleagueTextField

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
public class ColleagueTextField extends TextField implements TextListener, Colleague {
    private Mediator mediator;
    public ColleagueTextField(String text, int columns) {   
        super(text, columns);
    }
    public void setMediator(Mediator mediator) {            
        this.mediator = mediator;
    }
    public void setColleagueEnabled(boolean enabled) {      
        setEnabled(enabled);
        setBackground(enabled ? Color.white : Color.lightGray);
    }
    public void textValueChanged(TextEvent e) {             
        mediator.colleagueChanged();
    }
}

LoginFrame

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
public class LoginFrame extends Frame implements ActionListener, Mediator {
    private ColleagueCheckbox checkGuest;
    private ColleagueCheckbox checkLogin;
    private ColleagueTextField textUser;
    private ColleagueTextField textPass;
    private ColleagueButton buttonOk;
    private ColleagueButton buttonCancel;

    public LoginFrame(String title) {
        super(title);
        setBackground(Color.lightGray);
        setLayout(new GridLayout(4, 2));
        createColleagues();
        add(checkGuest);
        add(checkLogin);
        add(new Label("Username:"));
        add(textUser);
        add(new Label("Password:"));
        add(textPass);
        add(buttonOk);
        add(buttonCancel);
        colleagueChanged();
        pack();
        show();
    }

    public void createColleagues() {
        CheckboxGroup g = new CheckboxGroup();
        checkGuest = new ColleagueCheckbox("Guest", g, true);
        checkLogin = new ColleagueCheckbox("Login", g, false);
        textUser = new ColleagueTextField("", 10);
        textPass = new ColleagueTextField("", 10);
        textPass.setEchoChar('*');
        buttonOk = new ColleagueButton("OK");
        buttonCancel = new ColleagueButton("Cancel");
        checkGuest.setMediator(this);
        checkLogin.setMediator(this);
        textUser.setMediator(this);
        textPass.setMediator(this);
        buttonOk.setMediator(this);
        buttonCancel.setMediator(this);
        checkGuest.addItemListener(checkGuest);
        checkLogin.addItemListener(checkLogin);
        textUser.addTextListener(textUser);
        textPass.addTextListener(textPass);
        buttonOk.addActionListener(this);
        buttonCancel.addActionListener(this);
    }

    public void colleagueChanged() {
        if (checkGuest.getState()) { // Guest mode
            textUser.setColleagueEnabled(false);
            textPass.setColleagueEnabled(false);
            buttonOk.setColleagueEnabled(true);
        } else { // Login mode
            textUser.setColleagueEnabled(true);
            userpassChanged();
        }
    }
    private void userpassChanged() {
        if (textUser.getText().length() > 0) {
            textPass.setColleagueEnabled(true);
            if (textPass.getText().length() > 0) {
                buttonOk.setColleagueEnabled(true);
            } else {
                buttonOk.setColleagueEnabled(false);
            }
        } else {
            textPass.setColleagueEnabled(false);
            buttonOk.setColleagueEnabled(false);
        }
    }
    public void actionPerformed(ActionEvent e) {
        System.out.println(e.toString());
        System.exit(0);
    }
}

Mediator

1
2
3
4
public interface Mediator {
    public abstract void createColleagues();
    public abstract void colleagueChanged();
}

Main

1
2
3
4
5
6
public class Main {
    static public void main(String args[]) {
        new LoginFrame("Mediator Sample");
    }
}

0%