注:本文为译文,原文出处java-design-patterns-in-stories
简单来讲, 桥接模式是一个两层的抽象.
桥接模式意为：”分离抽象与实现, 从而使抽象与实现可以独立的区分开来”. 桥接使用封装,聚合,利用继承在不同类中分离出职责.
电视与遥控器(图内与错别字)的例子展示了两层抽象. 包含一个电视的接口和一个遥控器的抽象类. 如你所知, 为电视与遥控器创建具体的类并不是一个好主意, 因为他们的厂商会制造不同的实现.
首先, 定义一个电视的接口： ITV
public interface ITV {
public void on();
public void off();
public void switchChannel(int channel);
}
定义三星并实现ITV接口.
public class SamsungTV implements ITV {
@Override
public void on() {
System.out.println("Samsung is turned on.");
}
@Override
public void off() {
System.out.println("Samsung is turned off.");
}
@Override
public void switchChannel(int channel) {
System.out.println("Samsung: channel - " + channel);
}
}
定义索尼并实现ITV接口.
public class SonyTV implements ITV {
@Override
public void on() {
System.out.println("Sony is turned on.");
}
@Override
public void off() {
System.out.println("Sony is turned off.");
}
@Override
public void switchChannel(int channel) {
System.out.println("Sony: channel - " + channel);
}
}
遥控器持有电视的引用.
public abstract class AbstractRemoteControl {
/**
* @uml.property name="tv"
* @uml.associationEnd
*/
private ITV tv;
public AbstractRemoteControl(ITV tv){
this.tv = tv;
}
public void turnOn(){
tv.on();
}
public void turnOff(){
tv.off();
}
public void setChannel(int channel){
tv.switchChannel(channel);
}
}
定一个具体的遥控器类.
public class LogitechRemoteControl extends AbstractRemoteControl {
public LogitechRemoteControl(ITV tv) {
super(tv);
}
public void setChannelKeyboard(int channel){
setChannel(channel);
System.out.println("Logitech use keyword to set channel.");
}
}
public class Main {
public static void main(String[] args){
ITV tv = new SonyTV();
LogitechRemoteControl lrc = new LogitechRemoteControl(tv);
lrc.setChannelKeyboard(100);
}
}
输出:
Sony: channel - 100
Logitech use keyword to set channel.
总体来讲, 桥接模式允许两层抽象的实现, 在这种情况下, 电视和遥控器体现了这一点. 正因如此, 它来带来了更好的可扩展性.
桥接模式在Eclipse的架构在有着举足轻重的地位.