设计模式：中介者模式
什么是中介者模式
中介者模式是一种行为型模式。它把原来多对多的关系抽象成一对多的关系。
中介者模式的结构
-
Mediator：抽象中介者
-
ConcreteMediator：具体中介者
-
Colleague：抽象同事类
-
ConcreteColleagueA：具体同事类A
-
ConcreteColleagueB：具体同事类B
中介者模式的一个实例
一个简单的面板，面板上的元素有文本（LblDisplay）和三个按钮。三个按钮分别为BtnBook、BtnSearch和BtnView. 每当按下其中的某个按钮时，按下的按钮置成不可再点击状态，其他的两个按钮置成可点击状态。另外文本也显示相对应的文本。
实例代码
Command
public interface Command {
void execute();
}
LblDisplay
import javax.swing.*;
import java.awt.*;
public class LblDisplay extends JLabel {
Mediator med;
LblDisplay(Mediator m) {
super("Just start...");
med = m;
med.registerDisplay(this);
setFont(new Font("Arial", Font.BOLD, 24));
}
}
BtnBook
import javax.swing.*;
import java.awt.event.ActionListener;
public 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();
}
}
BtnSearch
import javax.swing.*;
import java.awt.event.ActionListener;
public 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();
}
}
BtnView
import javax.swing.*;
import java.awt.event.ActionListener;
public 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();
}
}
Mediator
public interface Mediator {
void book();
void view();
void search();
void registerView(BtnView v);
void registerSearch(BtnSearch s);
void registerBook(BtnBook b);
void registerDisplay(LblDisplay d);
}
PaticipantMediator
public 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...");
}
}
MediatorDemo
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public 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();
}
}
实例结果
（完）