中介者模式
中介者模式
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中介者模式定义:用一个中介对象封装一系列对象交互,中介者使各对象不需要显示地相互作用,从而使其耦合松散,而且可以独立地改变他们之间的交互(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)。
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中介者模式的通用类图如下:
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- Mediator抽象中介者角色,抽象中介者角色定义统一的接口,用于各同事角色之间通信。
- ConcreteMediator具体中介者角色,通过协调同事角色实现协作行为,因此必须依赖各个同事角色
- Colleague抽象同事类,指定中介者
- ConcreteColleague具体同事类,每个同事都知道中介者角色,而且在与其他的同事进行通信时,一定通过中介者角色的协调。每个同事类的角色分为两种,一种是处理同时本身的行为,比如改变对象本身的状态;一种是必须依赖中介者才能完成的行为,叫做依赖方法。
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public abstract class Mediator { //具体的同事类 protected ConcreteColleague1 colleague1; protected ConcreteColleague2 colleague2; public void setColleague1(ConcreteColleague1 colleague1){ this.colleague1 = colleague1; } public void setColleague2(ConcreteColleague2 colleague2){ this.colleague2 = colleague2; } //中介者模式的业务逻辑 public abstract void doSomething1(); public abstract void doSomething2(); } public class ConcreteMediator extends Mediator{ @Override public void doSomething1() { // TODO Auto-generated method stub super.colleague2.selfMethod(); } @Override public void doSomething2() { // TODO Auto-generated method stub super.colleague1.selfMethod(); } } public abstract class Colleague { protected Mediator mediator; public Colleague(Mediator mediator){ this.mediator = mediator; } } public class ConcreteColleague1 extends Colleague{ public ConcreteColleague1(Mediator mediator) { super(mediator); mediator.setColleague1(this); // TODO Auto-generated constructor stub } public void selfMethod(){ //该类自己的业务逻辑 System.out.println("This is a self-method"); } public void depMethod(){ //该类与其它类有关联的业务逻辑 super.mediator.doSomething1(); } } public class ConcreteColleague2 extends Colleague{ public ConcreteColleague2(Mediator mediator) { super(mediator); mediator.setColleague2(this); // TODO Auto-generated constructor stub } public void selfMethod(){ System.out.println("This is a self method in colleague2"); } public void depMethod(){ System.out.println("This is a dependent method in colleague2"); super.mediator.doSomething2(); } } public class Client { /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub Mediator mediator = new ConcreteMediator(); ConcreteColleague1 colleague1 = new ConcreteColleague1(mediator); ConcreteColleague2 colleague2 = new ConcreteColleague2(mediator); colleague1.depMethod(); colleague2.depMethod(); } }
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中介者模式的优点
中介者模式的优点是减少类间依赖,将原有的一对多的关系转化为一对一的依赖关系,同事类只依赖中介者,降低了类间的耦合。
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中介者模式的缺点
中介者模式的缺点是中介者会随着业务逻辑的增加而迅速膨胀,而且逻辑复杂,原本N个对象直接的相互依赖关系转化为中介者和同事类的依赖关系,同事类越多,中介者的逻辑越复杂。