22、中介者模式(Mediator)
22、中介者模式(Mediator)
中介者模式也是用来降低类类之间的耦合的,因为如果类类之间有依赖关系的话,不利于功能的拓展和维护,因为只要修改一个对象,其它关联的对象都得进行修改。如果使用中介者模式,只需关心和Mediator类的关系,具体类类之间的关系及调度交给Mediator就行,这有点像spring容器的作用。先看看图:
User类统一接口,User1和User2分别是不同的对象,二者之间有关联,如果不采用中介者模式,则需要二者相互持有引用,这样二者的耦合度很高,为了解耦,引入了Mediator类,提供统一接口,MyMediator为其实现类,里面持有User1和User2的实例,用来实现对User1和User2的控制。这样User1和User2两个对象相互独立,他们只需要保持好和Mediator之间的关系就行,剩下的全由MyMediator类来维护!基本实现:
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|
public
interface Mediator {
public void
createMediator();
public void
workAll();
} public
class MyMediator implements Mediator {
private User user1;
private User user2;
public User getUser1() {
return user1;
}
public User getUser2() {
return user2;
}
@Override
public void
createMediator() {
user1 = new
User1( this );
user2 = new
User2( this );
}
@Override
public void
workAll() {
user1.work();
user2.work();
}
} public
abstract class
User {
private Mediator mediator;
public Mediator getMediator(){
return mediator;
}
public User(Mediator mediator) {
this .mediator = mediator;
}
public abstract
void work();
} public
class User1 extends User {
public User1(Mediator mediator){
super (mediator);
}
@Override
public void
work() {
System.out.println( "user1 exe!" );
}
} public
class User2 extends User {
public User2(Mediator mediator){
super (mediator);
}
@Override
public void
work() {
System.out.println( "user2 exe!" );
}
} |
测试类:
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public
class Test {
public static
void main(String[] args) {
Mediator mediator = new
MyMediator();
mediator.createMediator();
mediator.workAll();
}
} |
输出:
user2 exe!