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();
}
}