【设计模式】命令模式

参考：B站动力节点

命令模式

定义：将一个请求封装成一个对象，从而我们可以用不同的请求对客户进行参数化。解决了应用程序中对象的职责以及它们之间的通信方式。实现了请求调用者和行为实现者的解耦。

举例说明，封装股票的买、卖命令（请求调用者），交由经纪人（行为实现者）执行。

interface Order{
	void execute();
}

// 股票类
class Stock{
	private String name = 'AAA';
	private int count = 10;

	public void buy(){
		System.out.println("买入[" + name + "]股票" + count + "个");
	}

	public void sell(){
		System.out.println("卖出[" + name + "]股票" + count + "个");
	}
}

// ------------------请求调用者封装类---------------------
class BuyOrder implements Order {
	private Stock stock;

	public BuyOrder(Stock stock) {
		this.stock = stock;
	}

	@Override
	public void execute(){
		stock.buy();
	}
}

class SellOrder implements Order {
	private Stock stock;

	public SellOrder(Stock stock){
		this.stock = stock;
	}

	@Override
	public void execute(){
		stock.sell();
	}
}

// ------------------行为实现者封装类---------------------
class Broker {
	List<Order> orderList = new ArrayList<>();

	public void takeOrder(Order order){
		orderList.add(order);
	}

	public void placeOrder(Order order){
		for (Order order : orderList) {
			order.execute();
		}
	}
}

运行逻辑：输入指令给Broker接收，Broker依次执行指令，实现了对命令的封装，请求者和执行者的解耦。

class Test{
	public static void main(String[] args) {
		Stock stock = new Stock();

		BuyOrder buy = new BuyOrder(stock);
		SellyOrder sell = new SellyOrder(stock);

		Broker broker = new Broker();
		broker.takeOrder(buy);
		broker.takeOrder(buy);
		broker.takeOrder(sell);

		broker.placeOrder();
	}
}