设计模式——命令模式

命令模式：

将请求封装成对象，从而使用不同的请求、队列以及日志来参数化其他对象。命令对象支持可撤销的操作。命令对象将动作和接收者包进对象中。实现“行为请求者”与“行为实现者”解耦。

要点： 命令对象中动作和接收者被绑在一起，控制器调用命令对象的execute方法。

应用： 线程池、队列请求、日志请求。

类图：

以下程序模拟一个控制器对客厅的灯和车库的门进行控制。


1.定义灯

package net.dp.command.simpleremote; public class Light {     public Light() {    }     public void on() {        System.out.println("Light is on");    }     public void off() {        System.out.println("Light is off");    }}

2.定义车库的门

package net.dp.command.simpleremote; public class GarageDoor {     public GarageDoor() {    }     public void up() {        System.out.println("Garage Door is Open");    }     public void down() {        System.out.println("Garage Door is Closed");    }     public void stop() {        System.out.println("Garage Door is Stopped");    }     public void lightOn() {        System.out.println("Garage light is on");    }     public void lightOff() {        System.out.println("Garage light is off");    }}

3.定义命令接口

package net.dp.command.simpleremote; public interface Command {    public void execute();}

4.实现命令接口

package net.dp.command.simpleremote; public class LightOnCommand implements Command {    Light light;       public LightOnCommand(Light light) {        this.light = light;    }      public void execute() {        light.on();    }}

package net.dp.command.simpleremote; public class LightOffCommand implements Command {    Light light;      public LightOffCommand(Light light) {        this.light = light;    }      public void execute() {        light.off();    }}

package net.dp.command.simpleremote; public class GarageDoorOpenCommand implements Command {    GarageDoor garageDoor;     public GarageDoorOpenCommand(GarageDoor garageDoor) {        this.garageDoor = garageDoor;    }     public void execute() {        garageDoor.up();    }}

5.编写控制器，实现命令的调用

package net.dp.command.simpleremote; //// This is the invoker//public class SimpleRemoteControl {    Command slot;      public SimpleRemoteControl() {}      public void setCommand(Command command) {        slot = command;    }      public void buttonWasPressed() {        slot.execute();    }}

6.写完啦！！

package net.dp.command.simpleremote; public class RemoteControlTest {    public static void main(String[] args) {        SimpleRemoteControl remote = new SimpleRemoteControl();        Light light = new Light();        GarageDoor garageDoor = new GarageDoor();        LightOnCommand lightOn = new LightOnCommand(light);        GarageDoorOpenCommand garageOpen = new GarageDoorOpenCommand(garageDoor);         remote.setCommand(lightOn);        remote.buttonWasPressed();        remote.setCommand(garageOpen);        remote.buttonWasPressed();    }}