中介者模式(Mediator Pattern)：
用一个中介对象（中介者）来封装一系列的对象交互，中介者使各对象不需要显式地相互引用，从而使其耦合松散，而且可以独立地改变它们之间的交互。
中介者模式又称为调停者模式，它是一种对象行为型模式。
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在中介者模式结构图中包含如下几个角色：
● Mediator（抽象中介者）：它定义一个接口，该接口用于与各同事对象之间进行通信。
● ConcreteMediator（具体中介者）：它是抽象中介者的子类，通过协调各个同事对象来实现
协作行为，它维持了对各个同事对象的引用。
● Colleague（抽象同事类）：它定义各个同事类公有的方法，并声明了一些抽象方法来供子类
实现，同时它维持了一个对抽象中介者类的引用，其子类可以通过该引用来与中介者通信。
● ConcreteColleague（具体同事类）：它是抽象同事类的子类；每一个同事对象在需要和其他
同事对象通信时，先与中介者通信，通过中介者来间接完成与其他同事类的通信；在具体同
事类中实现了在抽象同事类中声明的抽象方法。
QQ群
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public abstract class Member {
protected AbstractChatroom chatroom;
protected String name;
public Member(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public AbstractChatroom getChatroom() {
return chatroom;
}
public void setChatroom(AbstractChatroom chatroom) {
this.chatroom = chatroom;
}
public abstract void sendText(String to, String message);
public abstract void sendImage(String to, String image);
public void receiveText(String from, String message) {
System.out.println(from + "发送文本给" + this.name + "，内容为：" + message);
}
public void receiveImage(String from, String image) {
System.out.println(from + "发送图片给" + this.name + "，内容为：" + image);
}
}
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public class CommonMember extends Member {
public CommonMember(String name) {
super(name);
}
public void sendText(String to, String message) {
System.out.println("普通会员发送信息：");
chatroom.sendText(name, to, message); //发送
}
public void sendImage(String to, String image) {
System.out.println("普通会员不能发送图片！");
}
}
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public class DiamondMember extends Member {
public DiamondMember(String name) {
super(name);
}
public void sendText(String to, String message) {
System.out.println("钻石会员发送信息：");
chatroom.sendText(name, to, message); //发送
}
public void sendImage(String to, String image) {
System.out.println("钻石会员发送图片：");
chatroom.sendImage(name, to, image); //发送
}
}
public abstract class AbstractChatroom {
public abstract void register(Member member);
public abstract void sendText(String from, String to, String message);
public abstract void sendImage(String from, String to, String message);
}
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import java.util.Hashtable;
public class ChatGroup extends AbstractChatroom {
private Hashtable members = new Hashtable();
public void register(Member member) {
if (!members.contains(member)) {
members.put(member.getName(), member);
member.setChatroom(this);
}
}
public void sendText(String from, String to, String message) {
Member member = (Member) members.get(to);
String newMessage = message;
newMessage = message.replaceAll("日", "*");
member.receiveText(from, newMessage);
}
public void sendImage(String from, String to, String image) {
Member member = (Member) members.get(to);
//模拟图片大小判断
if (image.length() > 5) {
System.out.println("图片太大，发送失败！");
} else {
member.receiveImage(from, image);
}
}
}
public class Client {
public static void main(String args[]) {
AbstractChatroom happyChat = new ChatGroup();
Member member1, member2, member3, member4, member5;
member1 = new DiamondMember("张三");
member2 = new DiamondMember("李四");
member3 = new CommonMember("王五");
member4 = new CommonMember("小芳");
member5 = new CommonMember("小红");
happyChat.register(member1);
happyChat.register(member2);
happyChat.register(member3);
happyChat.register(member4);
happyChat.register(member5);
member1.sendText("李四", "李四，你好！");
member2.sendText("张三", "张三，你好！");
member1.sendText("李四", "今天天气不错，有日！");
member2.sendImage("张三", "一个很大很大的太阳");
member2.sendImage("张三", "太阳");
member3.sendText("小芳", "还有问题吗？");
member3.sendText("小红", "还有问题吗？");
member4.sendText("王五", "没有了，谢谢！");
member5.sendText("王五", "我也没有了！");
member5.sendImage("王五", "谢谢");
}
}
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客户信息管理窗口
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在图20-8中，Component充当抽象同事类，
Button、List、ComboBox和TextBox充当具体同事类，
Mediator充当抽象中介者类，
ConcreteMediator充当具体中介者类，
ConcreteMediator维持了对具体同事类的引用，为了简化ConcreteMediator类的代码，我们在其中只定义了一个Button对象和一个TextBox对象。
完整代码如下所示：
//抽象组件类：抽象同事类
abstract class Component {
protected Mediator mediator;
public void setMediator(Mediator mediator) {
this.mediator = mediator;
}
//转发调用
public void changed() {
mediator.componentChanged(this);
}
public abstract void update();
}
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//组合框类：具体同事类
class ComboBox extends Component {
public void update() {
System.out.println("组合框增加一项：张无忌。");
}
public void select() {
System.out.println("组合框选中项：小龙女。");
}
}
-----------------------------------------------------------------------------
//按钮类：具体同事类
class Button extends Component {
public void update() {
//按钮不产生交互
}
}
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//列表框类：具体同事类
class List extends Component {
public void update() {
System.out.println("列表框增加一项：张无忌。");
}
public void select() {
System.out.println("列表框选中项：小龙女。");
}
}
-----------------------------------------------------------------------------
//文本框类：具体同事类
class TextBox extends Component {
public void update() {
System.out.println("客户信息增加成功后文本框清空。");
}
public void setText() {
System.out.println("文本框显示：小龙女。");
}
}
//抽象中介者
abstract class Mediator {
public abstract void componentChanged(Component c);
}
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//具体中介者
class ConcreteMediator extends Mediator {
//维持对各个同事对象的引用
public Button addButton;
public List list;
public TextBox userNameTextBox;
public ComboBox cb;
//封装同事对象之间的交互
public void componentChanged(Component c) {
//单击按钮
if (c == addButton) {
System.out.println("--单击增加按钮--");
list.update();
cb.update();
userNameTextBox.update();
}
//从列表框选择客户
else if (c == list) {
System.out.println("--从列表框选择客户--");
cb.select();
userNameTextBox.setText();
}
//从组合框选择客户
else if (c == cb) {
System.out.println("--从组合框选择客户--");
cb.select();
userNameTextBox.setText();
}
}
}
class Client {
public static void main(String args[]) {
//定义中介者对象
ConcreteMediator mediator;
mediator = new ConcreteMediator();
//定义同事对象
Button addBT = new Button();
List list = new List();
ComboBox cb = new ComboBox();
TextBox userNameTB = new TextBox();
addBT.setMediator(mediator);
list.setMediator(mediator);
cb.setMediator(mediator);
userNameTB.setMediator(mediator);
mediator.addButton = addBT;
mediator.list = list;
mediator.cb = cb;
mediator.userNameTextBox = userNameTB;
addBT.changed();
System.out.println("-----------------------------");
list.changed();
}
}
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