中介者模式
范例 > Java

在以下示例中，一个中介者对象控制了三个互相交互的按钮的状态，为此它有设置状态的三个方法：book(), view() 和 search()。 当相应的按钮被激活时，对应的方法通过execute()方法被调用。
于是这里在交互中每个交互的参与者（本例中即按钮）将自己的行为提交给中介者并且由中介者将这些行为转给对应的参与者。
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

//Colleague interface
interface Command {
    void execute();
}

//Abstract Mediator
interface Mediator {
    void book();
    void view();
    void search();
    void registerView(BtnView v);
    void registerSearch(BtnSearch s);
    void registerBook(BtnBook b);
    void registerDisplay(LblDisplay d);
}

//Concrete mediator
class ParticipantMediator implements Mediator {

    BtnView btnView;
    BtnSearch btnSearch;
    BtnBook btnBook;
    LblDisplay show;

    //....
    public void registerView(BtnView v) {
        btnView = v;
    }

    public void registerSearch(BtnSearch s) {
        btnSearch = s;
    }

    public void registerBook(BtnBook b) {
        btnBook = b;
    }

    public void registerDisplay(LblDisplay d) {
        show = d;
    }

    public void book() {
        btnBook.setEnabled(false);
        btnView.setEnabled(true);
        btnSearch.setEnabled(true);
        show.setText("booking...");
    }

    public void view() {
        btnView.setEnabled(false);
        btnSearch.setEnabled(true);
        btnBook.setEnabled(true);
        show.setText("viewing...");
    }

    public void search() {
        btnSearch.setEnabled(false);
        btnView.setEnabled(true);
        btnBook.setEnabled(true);
        show.setText("searching...");
    }
    
}

//A concrete colleague
class BtnView extends JButton implements Command {

    Mediator med;

    BtnView(ActionListener al, Mediator m) {
        super("View");
        addActionListener(al);
        med = m;
        med.registerView(this);
    }

    public void execute() {
        med.view();
    }
    
}

//A concrete colleague
class BtnSearch extends JButton implements Command {

    Mediator med;

    BtnSearch(ActionListener al, Mediator m) {
        super("Search");
        addActionListener(al);
        med = m;
        med.registerSearch(this);
    }

    public void execute() {
        med.search();
    }
    
}

//A concrete colleague
class BtnBook extends JButton implements Command {

    Mediator med;

    BtnBook(ActionListener al, Mediator m) {
        super("Book");
        addActionListener(al);
        med = m;
        med.registerBook(this);
    }

    public void execute() {
        med.book();
    }

}

class LblDisplay extends JLabel {

    Mediator med;

    LblDisplay(Mediator m) {
        super("Just start...");
        med = m;
        med.registerDisplay(this);
        setFont(new Font("Arial", Font.BOLD, 24));
    }

}

class MediatorDemo extends JFrame implements ActionListener {

    Mediator med = new ParticipantMediator();

    MediatorDemo() {
        JPanel p = new JPanel();
        p.add(new BtnView(this, med));
        p.add(new BtnBook(this, med));
        p.add(new BtnSearch(this, med));
        getContentPane().add(new LblDisplay(med), "North");
        getContentPane().add(p, "South");
        setSize(400, 200);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent ae) {
        Command comd = (Command) ae.getSource();
        comd.execute();
    }

    public static void main(String[] args) {
        new MediatorDemo();
    }

}