Mediator模式

内容: Mediator模式看的有些快，基本概念和意思搞明白了。结合实际经验以前还没有碰到过适合用Mediator模式的场景。以后也尽量避免多类多对象之间的相互操作。OOD鼓励奖行为封装到各个对象中，也就是将变化点封装。但是有时候这种封装可能会导致对象间有许多连接。极端情况下，每个对象都知道其他所有对象。各个对象之间的交互比较多，每个对象的行为操作都依赖其他对象。修改一个对象的行为，很可能同时涉及到修改很多其他对象的行为。那么这时，可以使用Mediator模式将集体行为封装在一个“中介者对象中以避免这个问题。使用Mediator模式可以使各个对象间的耦合松散，只要关心每个对象和Mediator的关系，这样使多对多的关系变成了一对多的关系，每个对象都和Mediator联系。降低了系统得复杂性，提高了可扩展性和可修改性。 下面是实例代码：package Mediator;public abstract class Mediator{ public abstract void register(Colleague c, String type); public abstract void changed(String type);}//end class Mediatorpackage Mediator;public class ConcreteMediator extends Mediator{ private ColleagueA a; private ColleagueB b; private ColleagueC c; public ConcreteMediator() { //do something. }//end ConcreteMediator() public void register(Colleague colleague, String str) { if(str.equals('A')) { a = (ColleagueA)colleague; } else if (str.equals('B')) { b = (ColleagueB)colleague; } else if (str.equals('C')) { c = (ColleagueC)colleague; } }//end register() public void changed(String type) { if(type.equals('A')) { b.action(); c.action(); } else if (type.equals('B')) { a.action(); c.action(); } else if (type.equals('C')) { a.action(); b.action(); } }//end change() }//end class changed()package Mediator;public abstract class Colleague{ public abstract void change(); public abstract void action();}//end class Colleaguepackage Mediator;public class ColleagueA extends Colleague{ private final String type = 'A'; private Mediator med; public ColleagueA(Mediator m) { med = m; med.register(this, type); }//end ColleagueA() public void change() { System.out.println('---------- A changed now ! ----------'); med.changed(type); }//end change() public void action() { System.out.println(' A is changed by mediator '); }//end action() }//end class Colleaguepackage Mediator;public class ColleagueB extends Colleague{ private final String type = 'B'; private Mediator med; public ColleagueB(Mediator m) { med = m; med.register(this, type); }//end ColleagueB() public void change() { System.out.println('----- B changed now ! -----'); med.changed(type); }//end change() public void action() { System.out.println(' B is changed by mediator '); }//end action() }//end class ColleagueBpackage Mediator;public class ColleagueC extends Colleague{ private final String type = 'C'; private Mediator med; public ColleagueC(Mediator m) { med = m; med.register(this, type); }//end ColleagueC() public void change() { System.out.println('----- C changed now ! -----'); med.changed(type); }//end change() public void action() { System.out.println(' C is changed by mediator '); }//end action() }//end class ColleagueC/**//* * MediatorPattern.java * * Created on 2006年5月4日, 下午3:47 * * To change this template, choose Tools | Template Manager * and open the template in the editor. */package Mediator;/** *//** * * @author Administrator */public class MediatorPattern{ Mediator myMed = new ConcreteMediator(); ColleagueA ca = new ColleagueA(myMed); ColleagueB cb = new ColleagueB(myMed); ColleagueC cc = new ColleagueC(myMed); /** *//** Creates a new instance of MediatorPattern */ public MediatorPattern() { //do something. }//end MediatorPattern() public void showMediatorPattern() { ca.change(); cb.change(); cc.change(); }//end showMediatorPattern() public static void main(String[] args) { StringBuilder strb = new StringBuilder('The Mediator Pattern!'); System.out.println(strb.toString()); MediatorPattern mp = new MediatorPattern(); mp.showMediatorPattern(); }//end main() }//end class MediatorPattern下面是UML图： Java, java, J2SE, j2se, J2EE, j2ee, J2ME, j2me, ejb, ejb3, JBOSS, jboss, spring, hibernate, jdo, struts, webwork, ajax, AJAX, mysql, MySQL, Oracle, Weblogic, Websphere, scjp, scjd