1.定义:
将一个请求封装为一个对象,使发出请求的责任和执行请求的责任分割开。这样两者之间通过命令对象进行沟通,这样方便将命令对象进行存储、传递、调用、增加与管理。
命令模式包含以下主要角色:
将上面的案例用代码实现,那我们就需要分析命令模式的角色在该案例中由谁来充当。
服务员: 就是调用者角色,由她来发起命令。
资深大厨: 就是接收者角色,真正命令执行的对象。
订单: 命令中包含订单。
代码如下:
public interface Command { void execute();//只需要定义一个统一的执行方法 } public class OrderCommand implements Command { //持有接受者对象 private SeniorChef receiver; private Order order; public OrderCommand(SeniorChef receiver, Order order){ this.receiver = receiver; this.order = order; } public void execute() { System.out.println(order.getDiningTable() + "桌的订单:"); Set<String> keys = order.getFoodDic().keySet(); for (String key : keys) { receiver.makeFood(order.getFoodDic().get(key),key); } try { Thread.sleep(100);//停顿一下 模拟做饭的过程 } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(order.getDiningTable() + "桌的饭弄好了"); } } public class Order { // 餐桌号码 private int diningTable; // 用来存储餐名并记录份数 private Map<String, Integer> foodDic = new HashMap<String, Integer>(); public int getDiningTable() { return diningTable; } public void setDiningTable(int diningTable) { this.diningTable = diningTable; } public Map<String, Integer> getFoodDic() { return foodDic; } public void setFoodDic(String name, int num) { foodDic.put(name,num); } } // 资深大厨类 是命令的Receiver public class SeniorChef { public void makeFood(int num,String foodName) { System.out.println(num + "份" + foodName); } } public class Waitor { private ArrayList<Command> commands;//可以持有很多的命令对象 public Waitor() { commands = new ArrayList(); } public void setCommand(Command cmd){ commands.add(cmd); } // 发出命令 喊 订单来了,厨师开始执行 public void orderUp() { System.out.println("美女服务员:叮咚,大厨,新订单来了......."); for (int i = 0; i < commands.size(); i++) { Command cmd = commands.get(i); if (cmd != null) { cmd.execute(); } } } } public class Client { public static void main(String[] args) { //创建2个order Order order1 = new Order(); order1.setDiningTable(1); order1.getFoodDic().put("西红柿鸡蛋面",1); order1.getFoodDic().put("小杯可乐",2); Order order2 = new Order(); order2.setDiningTable(3); order2.getFoodDic().put("尖椒肉丝盖饭",1); order2.getFoodDic().put("小杯雪碧",1); //创建接收者 SeniorChef receiver=new SeniorChef(); //将订单和接收者封装成命令对象 OrderCommand cmd1 = new OrderCommand(receiver, order1); OrderCommand cmd2 = new OrderCommand(receiver, order2); //创建调用者 waitor Waitor invoker = new Waitor(); invoker.setCommand(cmd1); invoker.setCommand(cmd2); //将订单带到柜台 并向厨师喊 订单来了 invoker.orderUp(); } }
4.1 优点:
4.2 缺点: