中介者模式的定義
中介者模式的定義爲: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.(用一箇中介對象封裝一系列的對象交互,中介者使各對象不需要顯示地相互作用,從而使其耦合鬆散,而且可以獨立地改變它們之間的交互。)
中介者模式由以下幾個部分組成:
- Mediator抽象中介類
- Concrete Mediator具體中介者角色
- Colleague同事角色
中介者模式通用源碼
public abstract class Mediator {
protected ConcreteColleague1 c1;
protected ConcreteColleague2 c2;
public ConcreteColleague1 getC1() {
return c1;
}
public void setC1(ConcreteColleague1 c1) {
this.c1 = c1;
}
public ConcreteColleague2 getC2() {
return c2;
}
public void setC2(ConcreteColleague2 c2) {
this.c2 = c2;
}
//中介者模式的業務邏輯
public abstract void doSomething1();
public abstract void doSomething2();
}
public class ConcreteMediator extends Mediator {
@Override
public void doSomething1() {
super.c1.selfMethod1();
super.c2.selfMethod2();
}
@Override
public void doSomething2() {
super.c1.selfMethod1();
super.c2.selfMethod2();
}
}
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);
}
//自有方法
public void selfMethod1() {
//自己的邏輯
}
//依賴方法
public void depMethod1(){
super.mediator.doSomething1();
}
}
public class ConcreteColleague2 extends Colleague {
public ConcreteColleague2(Mediator mediator) {
super(mediator);
}
//自有方法
public void selfMethod2() {
//自己的邏輯
}
//依賴方法
public void depMethod2(){
super.mediator.doSomething2();
}
}
爲什麼同事類要使用構造函數注入中介者,而中介者使用getter/setter方式注入同事類呢?這是因爲同事類必須有中介者,而中介者卻可以只有部分同事類。
中介者模式的應用
優點
減少類間的依賴,降低類間的耦合
缺點
中介者類會膨脹的很大,而且邏輯複雜,同事類越多,中介者越複雜
使用場景
中介者模式適用於多個對象之間緊密耦合的情況,緊密耦合的標準是:在類圖中出現了蜘蛛網狀結構