设计模式-中介者（调停者）模式（行为型）

中介者模式

中介者模式是一种行为型模式，又叫调停者模式，它是为了解决多个对象之间，多个类之间通信的复杂性，定义一个中介者对象来封装一些列对象之间的交互，使各个对象之间不同持有对方的引用就可以实现交互，降低耦合度；实际开发中，消息队列、服务注册中心、MVC框架中的controller都是中介者；

图解

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角色

同事对象：定义抽象接口，用于与中介者进行通信，一般是一个发送消息的接口，一个接收消息的接口
具体同事对象：实现同事对象抽象接口，具体发送、接收消息的逻辑
中介者：定义要给抽象接口用于与同事对象进行通信
具体中介者：实现同事之间通信的逻辑

案例1-中介者持有同事对象的引用

中介者

public interface Mediator {void execute();
}
/** 实现1*/
public class AllPersonMediator implements Mediator {private List<Person> personList;public AllPersonMediator(List<Person> personList) {this.personList = personList;}@Overridepublic void execute() {System.out.println("开家长会啦：");personList.forEach(item -> System.out.println(item.getName()));}
}
/** 实现2*/
public class TeacherByTeacherMediator implements Mediator {private Person p1;private Person p2;public TeacherByTeacherMediator(Teacher p1, Teacher p2) {this.p1 = p1;this.p2 = p2;}@Overridepublic void execute() {System.out.println(p1.getName()+"和" + p2.getName() + "两个老师之间的协同的任务");}
}
/** 实现3*/
public class TeacherAndStudentAndParentsMediator implements Mediator {private Person p1;private Person p2;private Person p3;public TeacherAndStudentAndParentsMediator(Teacher p1, Student p2, Parents p3) {this.p1 = p1;this.p2 = p2;this.p3 = p3;}@Overridepublic void execute() {System.out.println("老师"+p1.getName()+"通知家长"+p3.getName() +"学生" +p2.getName()+ "成绩不及格！");}
}

同事类：

public abstract class Person {private String name;public Person(String name) {this.name = name;}public String getName() {return name;}
}public class Student extends Person {public Student(String name) {super(name);}
}public class Student extends Person {public Student(String name) {super(name);}
}public class Parents extends Person {public Parents(String name) {super(name);}
}

测试类：

public class Test01 {public static void main(String[] args) {Teacher t1 = new Teacher("王老师");Teacher t2 = new Teacher("刘老师");Student s1 = new Student("小明");Parents p1 = new Parents("小明爸爸");TeacherByStudentMediator teacherByTeacherMediator = new TeacherByStudentMediator(t1, s1);teacherByTeacherMediator.execute();TeacherAndStudentAndParentsMediator teacherAndStudentAndParentsMediator = new TeacherAndStudentAndParentsMediator(t1, s1, p1);teacherAndStudentAndParentsMediator.execute();List<Person> list = new ArrayList<>();list.add(t1);list.add(t2);list.add(s1);list.add(p1);AllPersonMediator allPersonMediator = new AllPersonMediator(list);allPersonMediator.execute();}
}

案例2-同事类持有中介者的引用

中介者

public interface SimpleMediator {Queue<Client> queue = new ConcurrentLinkedQueue<>();void add(Client c);Client get();
}
/** 实现*/
public class MessageSimpleMediator implements SimpleMediator{@Overridepublic void add(Client c) {queue.add(c);}@Overridepublic Client get() {return queue.poll();}
}

同事类

public abstract class Client<T> {protected String name;protected T message;protected SimpleMediator simpleMediator;public Client(String name, T message, SimpleMediator simpleMediator) {this.name = name;this.message = message;this.simpleMediator = simpleMediator;}public Client(String name, SimpleMediator simpleMediator) {this.name = name;this.simpleMediator = simpleMediator;}/** 发送消息*/abstract void sent();/** 获取消息*/abstract void get();public String getName() {return name;}public void setName(String name) {this.name = name;}public T getMessage() {return message;}public void setMessage(T message) {this.message = message;}
}public class ReceiverClient extends Client<String>{public ReceiverClient(String name, SimpleMediator simpleMediator) {super(name, simpleMediator);}@Overridevoid sent() {new RuntimeException("这是接收消息的客户端");}@Overridevoid get() {Client client = simpleMediator.get();System.out.println("发送人：" + client.getName());System.out.println("发送内容：" + client.getMessage());}
}public class SenderClient extends Client<String>{public SenderClient(String name, String message, SimpleMediator simpleMediator) {super(name, message, simpleMediator);}@Overridevoid sent() {simpleMediator.add(this);System.out.println("消息发送成功！");    }@Overridevoid get() {new RuntimeException("这是接收消息的客户端");}
}

测试类：

public class Test02 {public static void main(String[] args) {MessageSimpleMediator messageSimpleMediator = new MessageSimpleMediator();SenderClient C1 = new SenderClient("发送消息的客户端1", "发送的内容", messageSimpleMediator);SenderClient C2 = new SenderClient("发送消息的客户端2", "发送的内容", messageSimpleMediator);SenderClient C3 = new SenderClient("发送消息的客户端3", "发送的内容", messageSimpleMediator);ReceiverClient R3 = new ReceiverClient("接收消息的客户端",  messageSimpleMediator);C1.sent();C2.sent();C3.sent();while (messageSimpleMediator.queue.size() > 0){R3.get();}}
}