1 命令模式介绍

2 命令模式原理

3 命令模式实现

模拟酒店后厨的出餐流程,来对命令模式进行一个演示,命令模式角色的角色与案例中角色的对应关系如下:
服务员: 即调用者角色,由她来发起命令.
厨师: 接收者,真正执行命令的对象.
订单: 命令中包含订单

/**
 * 订单类
 **/
public class Order {

    private int diningTable;  //餐桌号码

    private Map<String,Integer> foodMenu = new HashMap<>();  //存储菜名和份数

    public int getDiningTable() {
        return diningTable;
    }

    public void setDiningTable(int diningTable) {
        this.diningTable = diningTable;
    }

    public Map<String, Integer> getFoodMenu() {
        return foodMenu;
    }

    public void setFoodMenu(Map<String, Integer> foodMenu) {
        this.foodMenu = foodMenu;
    }
}

/**
 * 厨师类 -> Receiver接收者角色
 **/
public class Chef {

    public void makeFood(int num , String foodName){
        System.out.println(num + "份, " + foodName);
    }
}

/**
 * 抽象命令接口
 **/
public interface Command {

    void execute(); //统一的执行方法
}

/**
 * 具体命令
 **/
public class OrderCommand implements Command {

    //接收者对象的引用
    private Chef receiver;

    private Order order;

    public OrderCommand(Chef receiver, Order order) {
        this.receiver = receiver;
        this.order = order;
    }

    @Override
    public void execute() {
        System.out.println(order.getDiningTable() + "桌的订单: ");
        Set<String> keySet = order.getFoodMenu().keySet();
        for (String key : keySet) {
            receiver.makeFood(order.getFoodMenu().get(key),key);
        }

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        System.out.println(order.getDiningTable() + "桌的菜品已经上齐!");
    }

}

/**
 * 服务员 -> Invoker 调用者
 **/
public class Waiter {

    //可以持有多个命令对象
    private ArrayList<Command> commands;

    public Waiter() {
        this.commands = new ArrayList<>();
    }

    public Waiter(ArrayList<Command> commands) {
        this.commands = commands;
    }

    public void setCommand(Command command) {
        this.commands.add(command);
    }

    //发出指令
    public void orderUp(){
        System.out.println("叮咚! 服务员: 有新的订单,请师傅开始制作......");
        for (Command command : commands) {
            if(command != null){
                command.execute();
            }
        }
    }
}

public class Client {

    public static void main(String[] args) {

        Order order1 = new Order();
        order1.setDiningTable(10);
        order1.getFoodMenu().put("鲍鱼炒饭",1);
        order1.getFoodMenu().put("海参炒面",1);

        Order order2 = new Order();
        order2.setDiningTable(15);
        order2.getFoodMenu().put("回锅肉盖饭",1);
        order2.getFoodMenu().put("木须肉盖饭",1);

        //创建接收者
        Chef chef = new Chef();

        //将订单和接收者封装成命令对象
        OrderCommand cmd1 = new OrderCommand(chef, order1);
        OrderCommand cmd2 = new OrderCommand(chef, order2);

        //创建调用者
        Waiter waiter = new Waiter();
        waiter.setCommand(cmd1);
        waiter.setCommand(cmd2);

        //将订单发送给厨师 上菜
        waiter.orderUp();
    }
}

4 命令模式总结