该文章是阅读《图解设计模式》的学习笔记。书本链接https://www.ituring.com.cn/book/1811
假如现在开发团队里面有十个人一起协同工作,但是对于程序的意见难以统一,总是相互指挥,这样极度影响工作进度。这时候就需要一个中立的仲裁者统一听取所有人的意见,然后从整个团队的利益出发进行决策仲裁。总的来说,就是组员向仲裁者报告,仲裁者向组员下达指示。如果把这一思想融入到编程中,就是Mediator仲裁者模式了。
Mediator接口代码:
package com.wen.Mediator;
public interface Mediator {
public abstract void createColleagues();
public abstract void colleagueChanged();
}
Colleague接口代码:
package com.wen.Mediator;
public interface Colleague {
public abstract void setMediator(Mediator mediator);
public abstract void setColleagueEnabled(boolean enabled);
}
ColleagueButton类代码:
package com.wen.Mediator;
import java.awt.Button;
public class ColleagueButton extends Button implements Colleague {
private Mediator mediator;
public ColleagueButton(String caption) {
super(caption);
}
public void setMediator(Mediator mediator) { // 保存Mediator
this.mediator = mediator;
}
public void setColleagueEnabled(boolean enabled) { // Mediator下达启用/禁用的指示
setEnabled(enabled);
}
}
ColleagueTextField类代码:
package com.wen.Mediator;
import java.awt.TextField;
import java.awt.Color;
import java.awt.event.TextListener;
import java.awt.event.TextEvent;
public class ColleagueTextField extends TextField implements TextListener, Colleague {
private Mediator mediator;
public ColleagueTextField(String text, int columns) { // 构造函数
super(text, columns);
}
public void setMediator(Mediator mediator) { // 保存Mediator
this.mediator = mediator;
}
public void setColleagueEnabled(boolean enabled) { // Mediator下达启用/禁用的指示
setEnabled(enabled);
setBackground(enabled ? Color.white : Color.lightGray);
}
public void textValueChanged(TextEvent e) { // 当文字发生变化时通知Mediator
mediator.colleagueChanged();
}
}
ColleagueCheckbox类代码:
package com.wen.Mediator;
import java.awt.Checkbox;
import java.awt.CheckboxGroup;
import java.awt.event.ItemListener;
import java.awt.event.ItemEvent;
public class ColleagueCheckbox extends Checkbox implements ItemListener, Colleague {
private Mediator mediator;
public ColleagueCheckbox(String caption, CheckboxGroup group, boolean state) { // 构造函数
super(caption, group, state);
}
public void setMediator(Mediator mediator) { // 保存Mediator
this.mediator = mediator;
}
public void setColleagueEnabled(boolean enabled) { // Mediator下达启用/禁用指示
setEnabled(enabled);
}
public void itemStateChanged(ItemEvent e) { // 当状态发生变化时通知Mediator
mediator.colleagueChanged();
}
}
LoginFrame类代码:
package com.wen.Mediator;
import java.awt.Frame;
import java.awt.Label;
import java.awt.Color;
import java.awt.CheckboxGroup;
import java.awt.GridLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
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;
// 构造函数。
// 生成并配置各个Colleague后,显示对话框。
public LoginFrame(String title) {
super(title);
setBackground(Color.lightGray);
// 使用布局管理器生成4×2窗格
setLayout(new GridLayout(4, 2));
// 生成各个Colleague
createColleagues();
// 配置
add(checkGuest);
add(checkLogin);
add(new Label("Username:"));
add(textUser);
add(new Label("Password:"));
add(textPass);
add(buttonOk);
add(buttonCancel);
// 设置初始的启用起用/禁用状态
colleagueChanged();
// 显示
pack();
show();
}
// 生成各个Colleague。
public void createColleagues() {
// 生成
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");
// 设置Mediator
checkGuest.setMediator(this);
checkLogin.setMediator(this);
textUser.setMediator(this);
textPass.setMediator(this);
buttonOk.setMediator(this);
buttonCancel.setMediator(this);
// 设置Listener
checkGuest.addItemListener(checkGuest);
checkLogin.addItemListener(checkLogin);
textUser.addTextListener(textUser);
textPass.addTextListener(textPass);
buttonOk.addActionListener(this);
buttonCancel.addActionListener(this);
}
// 接收来自于Colleage的通知然后判断各Colleage的启用/禁用状态。
public void colleagueChanged() {
if (checkGuest.getState()) { // Guest mode
textUser.setColleagueEnabled(false);
textPass.setColleagueEnabled(false);
buttonOk.setColleagueEnabled(true);
} else { // Login mode
textUser.setColleagueEnabled(true);
userpassChanged();
}
}
// 当textUser或是textPass文本输入框中的文字发生变化时
// 判断各Colleage的启用/禁用状态
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入口类代码:
package com.wen.Mediator;
import java.awt.*;
import java.awt.event.*;
public class Main {
static public void main(String args[]) {
new LoginFrame("Mediator Sample");
}
}
模式中的角色:
Mediator(仲裁者、中介者):扶着定义与Colleague(同事)角色进行通信和做出决定的API。如上面代码中的Mediator接口。
ConcreteMediator(具体的仲裁者):负责实现Mediator角色定义的接口。如上面代码中的LoginFrame类。
Colleague(同事):负责定义与Mediator角色进行通信的接口,如上面代码中的Colleague接口。
ConcreteColleague(具体的同事):负责实现Colleague的接口。如上面代码中的ColleagueButton、ColleagueTextField和ColleagueCheckbox这三个类。