设计模式之策略模式(一)

背景:

下单时有很多情况,有的是需要唤起支付,有的不需要支付,这样就需要写很多冗余代码,下面使用策略模式优化这种情况

代码结构

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
 
@RestController
@RequestMapping("/orders")
public class OrderController {
 
    @Autowired
    private OrderServiceImpl orderService;
 
    @PostMapping("/create/free")
    public OrderVO createFreeOrder(@RequestBody FreeOrderDTO freeOrderDTO) {
        freeOrderDTO.setOrderType("freeOrder");
        return orderService.createOrder(freeOrderDTO);
    }
 
    @PostMapping("/create/paid")
    public OrderVO createPaidOrder(@RequestBody PaidOrderDTO paidOrderDTO) {
        paidOrderDTO.setOrderType("paidOrder");
        return orderService.createOrder(paidOrderDTO);
    }
}

import org.springframework.stereotype.Service;
 
import javax.annotation.Resource;
 
@Service
public class OrderServiceImpl {
 
    @Resource
    private OrderCreationStrategyFactory strategyFactory;
 
    public OrderVO createOrder(OrderDTO orderDTO) {
        String orderType = orderDTO.getOrderType();
        OrderCreationStrategyextends OrderDTO> strategy = strategyFactory.getStrategy(orderType);
        if (strategy == null) {
            throw new IllegalArgumentException("No strategy found for order type: " + orderType);
        }
        return strategy.createOrder(orderDTO);
    }
}

import lombok.Data;
 
@Data
public class OrderVO {
    private String orderId;
    private String status;
    private double amount;
}

import lombok.Data;
 
@Data
public abstract class OrderDTO {
    private String orderType;
}
 
@Data
public class FreeOrderDTO extends OrderDTO {
    private String freeOrderDetail;
}
 
@Data
public class PaidOrderDTO extends OrderDTO {
    private double amount;
    private String paidOrderDetail;
}

策略类接口 

public interface OrderCreationStrategyextends OrderDTO> {
    OrderVO createOrder(T orderDTO);
}

免密支付策略类 

import org.springframework.stereotype.Component;
 
@Component
public class FreeOrderCreationStrategy implements OrderCreationStrategy {
 
    @Override
    public OrderVO createOrder(FreeOrderDTO orderDTO) {
        OrderVO orderVO = new OrderVO();
        orderVO.setOrderId(UUID.randomUUID().toString());
        orderVO.setStatus("FREE_ORDER_CREATED");
        orderVO.setAmount(0);
        return orderVO;
    }
}

需要支付的策略类 

import org.springframework.stereotype.Component;
 
@Component
public class PaidOrderCreationStrategy implements OrderCreationStrategy {
 
    @Override
    public OrderVO createOrder(PaidOrderDTO orderDTO) {
        OrderVO orderVO = new OrderVO();
        orderVO.setOrderId(UUID.randomUUID().toString());
        orderVO.setStatus("PAID_ORDER_CREATED");
        orderVO.setAmount(orderDTO.getAmount());
        return orderVO;
    }
}

策略类工厂 

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
 
import javax.annotation.PostConstruct;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
 
@Component
public class OrderCreationStrategyFactory {
 
    private static final Mapextends OrderDTO>> strategies = new ConcurrentHashMap<>();
 
    @Autowired
    private FreeOrderCreationStrategy freeOrderCreationStrategy;
 
    @Autowired
    private PaidOrderCreationStrategy paidOrderCreationStrategy;
 
    @PostConstruct
    public void init() {
        strategies.put("freeOrder", freeOrderCreationStrategy);
        strategies.put("paidOrder", paidOrderCreationStrategy);
    }
 
    public OrderCreationStrategyextends OrderDTO> getStrategy(String strategyType) {
        return strategies.get(strategyType);
    }
}