命令设计模式的应用

嗨，您好！

今天，我将与您分享一种非常出色的编程设计模式。它有很多用法，是我的最爱之一。编程设计模式命令具有多种用例。在这篇文章中，我们将看到如何实现现实世界中的某些东西。

我们将使用电子汽车钥匙来打开，关闭门，启用，禁用警报，打开，关闭车库门或打开和关闭汽车的引擎盖和行李箱。

我将向您展示的示例是一个非常普通的示例，因此您随时可以回到这里，并在您的应用程序中使用它。

UML命令模式

如您所知，我总是通过在UML图上显示类图来启动项目。这有助于我们以一种精巧，紧凑的方式修复该示例的概述。

command_action

解释细节编程设计

我们的客户是法拉利车主（FerrariCleint）。它有一个CarKey。 CarKey具有可通过命令配置的通用MicroShip（Involker）。命令（OpenDoorCommand）本身具有要执行的动作（DoorAction）。 CarKey可以配置do和undo命令。 NullObjectCommand属于Null对象设计模式，并且还将在此处使用。现在让我们在代码中查看实现细节。

指挥与微舰

NullObjectCommand在这里用于避免空指针异常，并且只要未定义任何命令就什么都不执行。

public interface Command {void execute();
}
public class MicroChip {protected Command[] onCommands;protected Command[] offCommands;public MicroChip(int commandQuantity) {onCommands =  new Command[commandQuantity];offCommands = new Command[commandQuantity];Command nullObjecCommand =  new NullObjectCommand();for (int i = 0; i < commandQuantity; i++) {onCommands[i]=nullObjecCommand;offCommands[i]=nullObjecCommand;}}public void configureCommand(int position, Command on, Command off){onCommands[position]=on;offCommands[position]=off;}public void executeOnCommand(int position){onCommands[position].execute();}public void executeOffCommand(int position){offCommands[position].execute();}protected class NullObjectCommand implements Command{@Overridepublic void execute() {// NULL-OBJECT-PATTERN}}
}

具体的命令和动作

在这里，我们可以看到Actions和Commands的具体实现。

public class Door {public void on(){System.out.println("Opening car doors...");}public void off(){System.out.println("Closing car doors...");}
}
public class OpenDoorCommand implements Command {private Door door;public OpenDoorCommand(Door door) {this.door = door;}@Overridepublic void execute() {door.on();}
}
public class CloseDoorCommand implements Command {private Door door;public CloseDoorCommand(Door door) {this.door =door;}@Overridepublic void execute() {door.off();}
}

通用微型船

如您在这里看到的，此实现或此MicroShip可以容纳所需数量的命令，并且可以在您可能需要的任何情况下重用。在此MicroShip波纹管中，我只实现了上面的OpenDoorCommand和CloseDoorCommand，因此您可以看到它的强大功能。像我一样，您还可以执行其他命令。这很酷的事情是执行和撤消操作的能力。创建所需数量的命令并执行所需的动作。这种图案的简单和美丽使我着迷。

public class CarKey {private MicroChip microChip;public CarKey() {final int commandQuantity = 5;microChip = new MicroChip(commandQuantity);final Hood hood = new Hood();final OpenHoodCommand openHoodCmd = new OpenHoodCommand(hood);final CloseHoodCommand closeHoodCmd = new CloseHoodCommand(hood);microChip.configureCommand(0, openHoodCmd, closeHoodCmd);final Door door = new Door();final OpenDoorCommand openDoorCmd = new OpenDoorCommand(door);final CloseDoorCommand closeDoorCmd = new CloseDoorCommand(door);microChip.configureCommand(1, openDoorCmd, closeDoorCmd);final Garage garage = new Garage();final OpenGarageCommand openGarageCmd = new OpenGarageCommand(garage);final CloseGarageCommand closeGarageCmd = new CloseGarageCommand(garage);microChip.configureCommand(2, openGarageCmd, closeGarageCmd);final Trunk trunk = new Trunk();final OpenTrunkCommand openTrunkCmd = new OpenTrunkCommand(trunk);final CloseTrunkCommand closeTrunkCmd = new CloseTrunkCommand(trunk);microChip.configureCommand(3, openTrunkCmd, closeTrunkCmd);final Alarm alarm = new Alarm();final EnableAlarmCommand enableAlarmCmd = new EnableAlarmCommand(alarm);final DisableAlarmCommand disableAlarmCmd = new DisableAlarmCommand(alarm);microChip.configureCommand(4, enableAlarmCmd, disableAlarmCmd);}public void openHood(){microChip.executeOnCommand(0);}public void closeHood(){microChip.executeOffCommand(0);}public void openDoor(){microChip.executeOnCommand(1);}public void closeDoor(){microChip.executeOffCommand(1);}public void openGarage(){microChip.executeOnCommand(2);}public void closeGarage(){microChip.executeOffCommand(2);}public void openTrunk(){microChip.executeOnCommand(3);}public void closeTrunk(){microChip.executeOffCommand(3);}public void enableAlarm(){microChip.executeOnCommand(4);}public void disableAlarm(){microChip.executeOffCommand(4);}}

法拉利客户

最后，我们可以看到这种漂亮的设计模式的用法和功能。在此示例中，我实现了多个命令来向您展示它的外观。

public class FerrariClient {public static void main(String[] args) {final CarKey ferrariSwitchbladeKey = new CarKey();ferrariSwitchbladeKey.openHood();ferrariSwitchbladeKey.openGarage();ferrariSwitchbladeKey.openTrunk();ferrariSwitchbladeKey.openDoor();ferrariSwitchbladeKey.enableAlarm();System.out.println("-------------------------------");ferrariSwitchbladeKey.closeHood();ferrariSwitchbladeKey.closeGarage();ferrariSwitchbladeKey.closeTrunk();ferrariSwitchbladeKey.closeDoor();ferrariSwitchbladeKey.disableAlarm();}
}

就这样。希望你喜欢！