无涯教程-Java 命令模式命令模式把一个请求或者操作封装到一个对象中。命令模式允许系统使用不同的请求把客户端参数化，对

命令模式把一个请求或者操作封装到一个对象中。命令模式允许系统使用不同的请求把客户端参数化，对请求排队或者记录请求日志，可以提供命令的撤销和恢复函数，属于行为模式类别。

命令模式实例

无涯教程创建了一个接口 Order 作为命令。创建了一个 Stock 类作为请求。有具体的命令类 BuyStock 和 SellStock 实现 Order 接口，它们将执行实际的命令处理，创建一个代理类，该类充当调用者对象，它可以接受和下订单。

代理对象使用命令模式来根据命令的类型识别哪个对象将执行哪个命令。演示类 CommandPatternDemo 将使用 Broker 类演示命令模式。

第1步 - 创建一个命令接口。

Order.java

public interface Order {
   void execute();
}

第2步 - 创建一个请求类。

Stock.java

public class Stock {
private String name = "ABC";
private int quantity = 10;
public void buy(){
System.out.println("Stock [ Name: "+name+",
Quantity: " + quantity +" ] bought");
}
public void sell(){
System.out.println("Stock [ Name: "+name+",
Quantity: " + quantity +" ] sold");
}
}

第3步 - 创建实现 Order 接口的具体类。

BuyStock.java

public class BuyStock implements Order {
   private Stock abcStock;
public BuyStock(Stock abcStock){
this.abcStock = abcStock;
}
public void execute() {
abcStock.buy();
}
}

SellStock.java

public class SellStock implements Order {
   private Stock abcStock;
public SellStock(Stock abcStock){
this.abcStock = abcStock;
}
public void execute() {
abcStock.sell();
}
}

第4步 - 创建命令调用程序类。

Broker.java

import java.util.ArrayList;
import java.util.List;
public class Broker {
private List<Order> orderList = new ArrayList<Order>();
public void takeOrder(Order order){
orderList.add(order);
}
public void placeOrders(){
  </span><span class="kwd">for</span><span class="pln"> </span><span class="pun">(</span><span class="typ">Order</span><span class="pln"> order </span><span class="pun">:</span><span class="pln"> orderList</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
     order</span><span class="pun">.</span><span class="pln">execute</span><span class="pun">();</span><span class="pln">
  </span><span class="pun">}</span><span class="pln">
  orderList</span><span class="pun">.</span><span class="pln">clear</span><span class="pun">();</span><span class="pln">

}
}

第5步 - 使用Broker类接收和执行命令。

CommandPatternDemo.java

public class CommandPatternDemo {
   public static void main(String[] args) {
      Stock abcStock = new Stock();
  </span><span class="typ">BuyStock</span><span class="pln"> buyStockOrder </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">BuyStock</span><span class="pun">(</span><span class="pln">abcStock</span><span class="pun">);</span><span class="pln">
  </span><span class="typ">SellStock</span><span class="pln"> sellStockOrder </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">SellStock</span><span class="pun">(</span><span class="pln">abcStock</span><span class="pun">);</span><span class="pln">

  </span><span class="typ">Broker</span><span class="pln"> broker </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Broker</span><span class="pun">();</span><span class="pln">
  broker</span><span class="pun">.</span><span class="pln">takeOrder</span><span class="pun">(</span><span class="pln">buyStockOrder</span><span class="pun">);</span><span class="pln">
  broker</span><span class="pun">.</span><span class="pln">takeOrder</span><span class="pun">(</span><span class="pln">sellStockOrder</span><span class="pun">);</span><span class="pln">

  broker</span><span class="pun">.</span><span class="pln">placeOrders</span><span class="pun">();</span><span class="pln">

}
}

第6步 - 验证输出。

Stock [ Name: ABC, Quantity: 10 ] bought
Stock [ Name: ABC, Quantity: 10 ] sold

无涯教程-Java 命令模式

命令模式实例

参考链接