《中介者模式》PPT课件.ppt
第十二章 中介者模式,2023/7/9,1,中介者模式 用一个中介对象来封装一系列的对象交互。中介者使各对象不需要显示地相互引用,从而使其耦合松散,而且可以独立地改变它们之间的交互。Mediator Pattern Define an object that encapsulates how a set of objects interact.Mediator promotes loose coupling by keeping objects from referring to each other explicitly,and it lets you vary their interaction independently.,一、概述,2023/7/9,3,中介者模式是封装一系列的对象交互的成熟模式,其关键是将对象之间的交互封装在称作中介者的对象中,中介者使各对象不需要显示地相互引用,这些对象只包含中介者的引用。当系统中某个对象需要和系统中另外一个对象交互时,只需将自己的请求通知中介者即可。,二、中介者模式的结构与使用,2023/7/9,4,模式的结构中包括四种角色:中介者(Mediator)具体中介者(ConcreteMediator)同事(Colleague)具体同事(ConcreteColleague),2023/7/9,5,模式的UML类图,模式的结构的描述与使用,古代相互交战的A,B,C三方,想通过一个中介者调停之间的战火。A方委托调停者转达的信息是:“要求B方归还曾抢夺的100斤土豆,要求C方归还曾抢夺的20头牛”;B方委托调停者转达的信息是:“要求A方归还曾抢夺的10只鸡,要求C方归还曾抢夺的15匹马”;C方委托调停者转达的信息是:“要求A方归还曾抢夺的300斤小麦,要求B方归还曾抢夺的50头驴”。,2023/7/9,8,1同事(Colleague):Colleague.java public interface Colleague public void giveMess(String mess);public void receiverMess(String mess);public void setName(String name);public String getName();注:本问题中,只需要一个具体中介者,我们并不需要一个中介者(Mediator)接口。,2023/7/9,9,2具体中介者(Mediator):ConcreteMediator.java public class ConcreteMediator ColleagueA colleagueA;ColleagueB colleagueB;ColleagueC colleagueC;public void registerColleagueA(ColleagueA colleagueA)this.colleagueA=colleagueA;public void registerColleagueB(ColleagueB colleagueB)this.colleagueB=colleagueB;public void registerColleagueC(ColleagueC colleagueC)this.colleagueC=colleagueC;,public void deliverMess(Colleague colleague,String mess)if(colleague=colleagueA)if(mess.length=2)colleagueB.receiverMess(colleague.getName()+mess0);colleagueC.receiverMess(colleague.getName()+mess1);else if(colleague=colleagueB)if(mess.length=2)colleagueA.receiverMess(colleague.getName()+mess0);colleagueC.receiverMess(colleague.getName()+mess1);else if(colleague=colleagueC)if(mess.length=2)colleagueA.receiverMess(colleague.getName()+mess0);colleagueB.receiverMess(colleague.getName()+mess1);,2023/7/9,11,3具体同事(ConcreteColleague)_1:ColleagueA.java public class ColleagueA implements Colleague ConcreteMediator mediator;String name;ColleagueA(ConcreteMediator mediator)this.mediator=mediator;mediator.registerColleagueA(this);public void setName(String name)this.name=name;public String getName()return name;public void giveMess(String mess)mediator.deliverMess(this,mess);public void receiverMess(String mess)System.out.println(name+收到的信息:);System.out.println(t+mess);,2023/7/9,12,3具体同事(ConcreteColleague)_2:ColleagueB.java public class ColleagueB implements Colleague ConcreteMediator mediator;String name;ColleagueB(ConcreteMediator mediator)this.mediator=mediator;mediator.registerColleagueB(this);public void setName(String name)this.name=name;public String getName()return name;public void giveMess(String mess)mediator.deliverMess(this,mess);public void receiverMess(String mess)System.out.println(name+收到的信息:);System.out.println(t+mess);,2023/7/9,13,3具体同事(ConcreteColleague)_3:ColleagueC.java public class ColleagueC implements Colleague ConcreteMediator mediator;String name;ColleagueC(ConcreteMediator mediator)this.mediator=mediator;mediator.registerColleagueC(this);public void setName(String name)this.name=name;public String getName()return name;public void giveMess(String mess)mediator.deliverMess(this,mess);public void receiverMess(String mess)System.out.println(name+收到的信息:);System.out.println(t+mess);,2023/7/9,14,4应用 Application.java public class Application public static void main(String args)ConcreteMediator mediator=new ConcreteMediator();ColleagueA colleagueA=new ColleagueA(mediator);ColleagueB colleagueB=new ColleagueB(mediator);ColleagueC colleagueC=new ColleagueC(mediator);colleagueA.setName(A国);colleagueB.setName(B国);colleagueC.setName(C国);String messA=要求归还曾抢夺的100斤土豆,要求归还曾抢夺的20头牛;colleagueA.giveMess(messA);String messB=要求归还曾抢夺的10只公鸡,要求归还曾抢夺的15匹马;colleagueB.giveMess(messB);String messC=要求归还曾抢夺的300斤小麦,要求归还曾抢夺的50头驴;colleagueC.giveMess(messC);,三、中介者模式的优点,2023/7/9,15,可以避免许多的对象为了之间的通信而相互显示引用,不仅系统难于维护,而且也使其他系统难以复用这些对象。可以通过中介者将原本分布于多个对象之间的交互行为集中在一起。当这些对象之间需要改变之间的通信行为时,只需使用一个具体中介者即可,不必修改各个具体同事的代码,即这些同事可被重用。具体中介者使得各个具体同事完全解耦,修改任何一个具体同事的代码不会影响到其他同事。具体中介者集中了同事之间是如何交互的细节,使得系统比较清楚地知道整个系统中的同事是如何交互的。当一些对象想互相通信,但又无法相互包含对方的引用,那么使用中介者模式就可以使得这些对象互相通信。,四、适合使用中介者模式的情景,许多对象以复杂的方式交互,所导致的依赖关系使系统难以理解和维护。一个对象引用其他很多对象,导致难以复用该对象。,