命令设计模式

可将请求转换为一个包含与请求相关的所有信息的独立对象。该转换让你能根据不同的请求将方法参数化、延迟请求执行或将其放入队列中，且能实现可撤销操作。此外，命令设计模式在web开发中不常见，常用于GUI的开发中。

需求分析

小米搬新家了，他想实现智能家居，开发一个app，可以控制家里的家电，比如控制空调的开关、加热、制冷等功能。利用命令设计模式，帮小米完成这个需求，注意：动作请求者就是手机app, 动作的执行者是家电的不同功能

编码实现

创建接收者

public class ConditionReceiver {

    public void on(){
        System.out.println("开启空调");
    }

    public void off(){
        System.out.println("关闭空调");
    }

    public void cool(){
        System.out.println("制冷模式");
    }

    public void warm(){
        System.out.println("制热模式");
    }
}

创建执行命令的抽象接口

public interface Command {

    /**
     * 执行动作
     */
    void execute();

}

四个接口实现类

public class OnCommand implements Command{

    /**
     * 对哪个receiver进行命令调用
     */
    private ConditionReceiver receiver;

    public OnCommand(ConditionReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        System.out.println("OnCommand -> execute");
        receiver.on();
    }
}


public class OffCommand implements Command{

    /**
     * 对哪个receiver进行命令调用
     */
    private ConditionReceiver receiver;

    public OffCommand(ConditionReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        System.out.println("OffCommand -> execute");
        receiver.off();
    }
}


public class CoolCommand implements Command{

    /**
     * 对哪个receiver进行命令调用
     */
    private ConditionReceiver receiver;

    public CoolCommand(ConditionReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        System.out.println("CoolCommand -> execute");
        receiver.cool();
    }
}

public class WarmCommand implements Command{

    /**
     * 对哪个receiver进行命令调用
     */
    private ConditionReceiver receiver;

    public WarmCommand(ConditionReceiver receiver) {
        this.receiver = receiver;
    }

    @Override
    public void execute() {
        System.out.println("WarmCommand -> execute");
        receiver.warm();
    }
}

创建请求者

@Setter
public class AppInvoker {

    private Command onCommand;
    private Command offCommand;
    private Command coolCommand;
    private Command warmCommand;

    public void on() {
        onCommand.execute();
    }

    public void off() {
        offCommand.execute();
    }

    public void warm() {
        warmCommand.execute();
    }

    public void cool() {
        coolCommand.execute();
    }
}

使用

public static void main(String[] args) {
    // 创建接收者，空调
    ConditionReceiver receiver = new ConditionReceiver();

    // 创建命令对象，设定命令接收者
    Command onCommand = new OnCommand(receiver);
    Command offCommand = new OffCommand(receiver);
    Command coolCommand = new CoolCommand(receiver);
    Command warmCommand = new WarmCommand(receiver);

    // 创建请求者，把命令对象设置进去，app就是请求发起者
    AppInvoker appInvoker = new AppInvoker();
    appInvoker.setOnCommand(onCommand);
    appInvoker.setOffCommand(offCommand);
    appInvoker.setCoolCommand(coolCommand);
    appInvoker.setWarmCommand(warmCommand);

    // 发出命令
    appInvoker.on();
    appInvoker.cool();
}