只有一個(gè)仲裁者

Mediator 模式

組員向仲裁者報(bào)告，仲裁者向組員下達(dá)指示，組員之間不在相互詢問和相互指示。

要調(diào)整多個(gè)對(duì)象之間的關(guān)系時(shí)，就需要用到 Mediator 模式。將邏輯處理交給仲裁者執(zhí)行。

示例程序

Mediator.java

package mediator;

public interface Mediator {
    public abstract void createColleague();
    public abstract void colleagueChanged();
}

Colleague.java

package mediator;

public interface Colleague {
    public abstract void setMediator(Mediator mediator);
    public abstract void setColleagueEnabled(boolean enabled);
}

ColleagueButton.java

package mediator;

import java.awt.*;

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);
    }
}

ColleagueTextField.java

package mediator;

import java.awt.*;
import java.awt.event.TextEvent;
import java.awt.event.TextListener;

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();
    }
}

ColleagueCheckbox.java

package mediator;

import java.awt.*;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;

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);
        setBackground(enabled ? Color.WHITE : Color.lightGray);
    }
    public void itemStateChanged(ItemEvent e) {
        mediator.colleagueChanged();
    }
}

LoginFrame.java

package mediator;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

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;

    // 構(gòu)造函數(shù)
    // 生成并配置各個(gè)Colleague后，顯示對(duì)話框
    public LoginFrame(String title) {
        super(title);
        setBackground(Color.lightGray);
        setLayout(new GridLayout(4, 2));
        createColleague();
        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 createColleague() {
        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()) {
            textUser.setColleagueEnabled(false);
            textPass.setColleagueEnabled(false);
            buttonOk.setColleagueEnabled(true);
        } else {
            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);
    }
}

Main.java

package mediator;

public class Main {
    static public void main(String args[]) {
        new LoginFrame("Mediator Sample");
    }
}

Mediator 模式中的角色

1. Mediator(仲裁者、中介者)

   Mediator 角色負(fù)責(zé)定義與 Colleague 角色進(jìn)行通信和做出決定的接口。

2. ConcreteMediator(具體的仲裁者、中介者)

   ConcreteMediator 角色負(fù)責(zé)實(shí)現(xiàn) Mediator 角色的接口，負(fù)責(zé)實(shí)際做出決定。

3. Colleague(同事)

   Colleague 角色負(fù)責(zé)定義與 Mediator 角色進(jìn)行通信的接口。

4. ConcreteColleague(具體的同事)

   ConcreteColleague 角色負(fù)責(zé)實(shí)現(xiàn) Colleague 角色的接口。

拓展思路

一、Bug容易定位，因?yàn)闆]有別的控制控件做邏輯控制處理。

二、ConcreteColleague 角色可以復(fù)用，ConcreteMediator 角色難以復(fù)用。