Java设计模式之代表模式

代表模式（Mediator Pattern）是一种行为型设计模式，它通过封装一组对象之间的交互方式，使得这些对象之间的通信变得松散耦合，从而降低了对象之间的直接依赖关系。代表模式通过引入一个中介者（Mediator）对象，将对象之间的通信集中处理，从而减少了对象之间的相互依赖，使得系统更加灵活和可扩展。

在代表模式中，中介者对象充当了对象之间的调度者和协调者的角色，它封装了对象之间的通信逻辑，负责接收和发送消息，并将消息传递给相关的对象。对象之间不再直接相互引用，而是通过中介者对象进行通信，从而达到松散耦合的效果。

以下是一个示例，展示了代表模式的应用场景和代码实现：

// 中介者接口
interface Mediator {void sendMessage(String message, Colleague colleague);
}// 具体中介者
class ConcreteMediator implements Mediator {private Colleague colleague1;private Colleague colleague2;public void setColleague1(Colleague colleague1) {this.colleague1 = colleague1;}public void setColleague2(Colleague colleague2) {this.colleague2 = colleague2;}@Overridepublic void sendMessage(String message, Colleague colleague) {if (colleague == colleague1) {colleague2.receiveMessage(message);} else if (colleague == colleague2) {colleague1.receiveMessage(message);}}
}// 抽象同事类
abstract class Colleague {protected Mediator mediator;public Colleague(Mediator mediator) {this.mediator = mediator;}public abstract void send(String message);public abstract void receiveMessage(String message);
}// 具体同事类
class ConcreteColleague1 extends Colleague {public ConcreteColleague1(Mediator mediator) {super(mediator);}@Overridepublic void send(String message) {mediator.sendMessage(message, this);}@Overridepublic void receiveMessage(String message) {System.out.println("ConcreteColleague1 received message: " + message);}
}// 具体同事类
class ConcreteColleague2 extends Colleague {public ConcreteColleague2(Mediator mediator) {super(mediator);}@Overridepublic void send(String message) {mediator.sendMessage(message, this);}@Overridepublic void receiveMessage(String message) {System.out.println("ConcreteColleague2 received message: " + message);}
}// 测试代码
public class MediatorPatternExample {public static void main(String[] args) {ConcreteMediator mediator = new ConcreteMediator();ConcreteColleague1 colleague1 = new ConcreteColleague1(mediator);ConcreteColleague2 colleague2 = new ConcreteColleague2(mediator);mediator.setColleague1(colleague1);mediator.setColleague2(colleague2);colleague1.send("Hello from colleague1!");colleague2.send("Hi from colleague2!");}
}

在上面的示例中，Mediator 接口定义了中介者的操作，ConcreteMediator 是具体的中介者实现。Colleague 是抽象同事类，ConcreteColleague1 和 ConcreteColleague2 是具体的同事类实现。

在 MediatorPatternExample 类中，我们创建了一个中介者对象 ConcreteMediator，并创建了两个同事对象 ConcreteColleague1 和 ConcreteColleague2。然后，通过调用 setColleague1 和 setColleague2 方法将同事对象注册到中介者中。

最后，我们通过调用同事对象的 send 方法发送消息，消息会经过中介者进行转发，最终到达目标同事对象，从而实现了对象之间的通信。