java 策略模式的使用

• 一、为什么要用到策略模式
• 二、代码实现

1.接口类

public interface CreateOrderService {

    
    CreateOrderDto createOrder(CreateOrderVm createOrderVm);

}

2.多个接口实现类

@Service
public class CreateAdvanceOrderImpl implements CreateOrderService {

    @Override
    public CreateOrderDto createOrder(CreateOrderVm createOrderVm) {
        System.out.println("创建先行订单");
        return null;
    }
}

@Service
public class CreateReserveOrderImpl implements CreateOrderService {
    @Override
    public CreateOrderDto createOrder(CreateOrderVm createOrderVm) {
        System.out.println("创建预定订单");
        return null;
    }
}

@Service
public class CreateOrderImpl implements CreateOrderService {
    @Override
    public CreateOrderDto createOrder(CreateOrderVm createOrderVm) {
        System.out.println("创建现货订单");
        return null;
    }
}

3.枚举类

public enum CreateOrderStrategyEnum {

    先行(0, "com.gemo.bear.service.order.impl.CreateAdvanceOrderImpl"),
    定金预定(3, "com.gemo.bear.service.order.impl.CreateReserveOrderImpl"),
    现货(6, "com.gemo.bear.service.order.impl.CreateOrderImpl");

    private Integer openStart; //状态
    private String objectPath;//类的完全限定名：包名+类名

    CreateOrderStrategyEnum(Integer openStart, String objectPath) {
        this.openStart = openStart;
        this.objectPath = objectPath;
    }

    public static String getCreateOrderObject(Integer openStart) {
        for (CreateOrderStrategyEnum value : CreateOrderStrategyEnum.values()) {
            if (openStart == value.openStart) {
                return value.objectPath;
            }
        }
        return null;
    }
}

4.策略类

public class CreateOrderStrategy {

    private CreateOrderService createOrderService;

    
    public CreateOrderStrategy(CreateOrderService createOrderService) {
        this.createOrderService = createOrderService;
    }

    
    public CreateOrderDto createOrder(CreateOrderVm createOrderVm) {
        return this.createOrderService.createOrder(createOrderVm);
    }
}

5.策略类的使用

    @ApiOperation("订单创建")
    @PostMapping("create-order-test")
    public ResponseBuild createOrderTest(@Validated @RequestBody CreateOrderVm createOrderVm)  {
        try {
            //类的完全限定名：包名+类名
            String object = CreateOrderStrategyEnum.getCreateOrderObject(createOrderVm.getOpenState());
            //调用无参构造器创建实例
            CreateOrderService createOrderService = (CreateOrderService) Class.forName(object).newInstance();
            CreateOrderStrategy createOrderStrategy = new CreateOrderStrategy(createOrderService);
            return ResponseBuild.success(createOrderStrategy.createOrder(createOrderVm));
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }