设计模式之策略模式(一)

背景:

下单时有很多情况,有的是用户下单,有的是卡密下单,有的是下游下单,有的是需要唤起支付,有的不需要支付,这样就需要写很多下单接口,下面使用策略模式优化这种情况

代码结构

com.example.order
├── controller
│   └── OrderController.java
├── service
│   ├── OrderService.java
│   └── impl
│       └── OrderServiceImpl.java
├── strategy
│   ├── OrderStrategy.java
│   ├── factory
│   │   └── OrderStrategyFactory.java
│   ├── impl
│   │   ├── UserOrderStrategy.java
│   │   └── CardOrderStrategy.java
├── dto
│   └── OrderDTO.java
├── vo
│   ├── UserOrderVO.java
│   └── CardOrderVO.java
├── mapper
│   ├── OrderMapper.java
│   └── xml
│       └── OrderMapper.xml
├── domain
│   └── OrderDO.java

@RestController
@RequestMapping("/orders")
public class OrderController {@Autowiredprivate OrderService orderService;@PostMapping("/create")public ResponseEntity<?> createOrder(@RequestBody OrderDTO orderDTO) {Object orderVO = orderService.createOrder(orderDTO);return new ResponseEntity<>(orderVO, HttpStatus.OK);}
}

@Service
public class OrderServiceImpl implements OrderService {@Override@SuppressWarnings("unchecked")public <T> T createOrder(OrderDTO orderDTO) {OrderStrategy<T> strategy = OrderStrategyFactory.getStrategy(orderDTO.getOrderType());return strategy.createOrder(orderDTO);}
}

策略类接口 

public interface OrderStrategy<T> {T createOrder(OrderDTO orderDTO);
}

用户下单策略类 

public class UserOrderStrategy implements OrderStrategy<UserOrderVO> {@Overridepublic UserOrderVO createOrder(OrderDTO orderDTO) {// 用户下单的具体处理逻辑// 生成订单并保存到数据库// 返回UserOrderVO对象UserOrderVO userOrderVO = new UserOrderVO();// 设置相关属性return userOrderVO;}
}

卡密下单策略类 

public class CardOrderStrategy implements OrderStrategy<CardOrderVO> {@Overridepublic CardOrderVO createOrder(OrderDTO orderDTO) {// 卡密下单的具体处理逻辑// 生成订单并保存到数据库// 返回CardOrderVO对象CardOrderVO cardOrderVO = new CardOrderVO();// 设置相关属性return cardOrderVO;}
}

策略类工厂 

import java.util.HashMap;
import java.util.Map;public class OrderStrategyFactory {private static final Map<String, OrderStrategy<?>> strategies = new HashMap<>();static {strategies.put("USER_ORDER", new UserOrderStrategy());strategies.put("CARD_ORDER", new CardOrderStrategy());// 初始化其他订单类型的策略}@SuppressWarnings("unchecked")public static <T> OrderStrategy<T> getStrategy(String orderType) {OrderStrategy<?> strategy = strategies.get(orderType);if (strategy == null) {throw new IllegalArgumentException("Unknown order type: " + orderType);}return (OrderStrategy<T>) strategy;}
}

public class UserOrderVO {private String orderId;private String status;private String userSpecificInfo;// 其他用户订单特有属性// Getters and Setters
}public class CardOrderVO {private String orderId;private String status;private String cardCode;// 其他卡密订单特有属性// Getters and Setters
}

public interface OrderMapper {void insertOrder(OrderDO orderDO);// 其他数据库操作方法
}

<mapper namespace="com.example.mapper.OrderMapper"><insert id="insertOrder" parameterType="OrderDO">INSERT INTO orders (order_id, user_id, order_type, payment_type, status)VALUES (#{orderId}, #{userId}, #{orderType}, #{paymentType}, #{status})</insert><!-- 其他数据库操作的XML定义 -->
</mapper>