与春豆的战略模式

Question

说我用春天,我有以下策略......

接口

public interface MealStrategy {
    cook(Meat meat);
}

第一战略

@Component
public class BurgerStrategy  implements
MealStrategy {
  @Autowired CookerDao cookeryDao;

  @Override
  public void cook(Meat meat) {
      cookeryDao.getBurger(meat);
  }
}

下一步策略......

@Component
public class SausageStrategy  implements
MealStrategy {
  @Autowired CookerDao cookeryDao;

  @Override
  public cook(Meat meat) {
      return cookeryDao.getSausage(meat);
  }
}

背景...

@Component
@Scope("prototype")
public class MealContext {
    private MealStrategy mealStrategy;

    public void setMealStrategy(MealStrategy strategy) {
        this.strategy = strategy;
    }

    public void cookMeal(Meat meat) {
        mealStrategy.cook;
    }
}

现在说这个上下文是通过mvc控制器访问的,比如...

@Autowired
private MealContext mealContext;

@RequestMapping(method = RequestMethod.POST)
public @ResponseBody Something makeMeal(Meat meat) {
    mealContext.setMealStrategy(new BurgerStrategy())
    mealContext.cookMeal(meat);
}

上下文应该是一个组成部分吗？当我这样做时,我得到一个错误,说loadOnStartup,就像你期望的那样,策略可以是一个nonUniqueBean.所有的bean都需要像上面这样的组件,还是我的注释不正确？

我最大的疑问是你可以在Spring MVC应用程序中使用这样的上下文吗？我使用@Scope(原型)时遇到的问题是它意味着策略中的cookeryDao调用会返回一个空指针,因为Dao不会被注入.

如何使用弹簧实现上述模式并且还是线程安全的？我正在尝试甚至可能吗？

Answer 1

由于具体策略通常在运行时根据提供的参数确定,因此我建议如下.

@Component
public class BurgerStrategy implements MealStrategy { ... }

@Component
public class SausageStrategy implements MealStrategy { ... }

然后将所有这些策略注入到给定控制器中的映射(以bean名称作为键)并根据请求选择相应的策略.

@Autowired
Map<String, MealStrategy> mealStrategies = new HashMap<>;

@RequestMapping(method=RequestMethod.POST)
public @ResponseBody Something makeMeal(@RequestParam(value="mealStrategyId") String mealStrategyId, Meat meat) {
    mealStrategies.get(mealStrategyId).cook(meat);

    ...
}

Answer 2

我会使用简单的依赖注入.

@Component("burger")
public class BurgerStrategy implements MealStrategy { ... }

@Component("sausage")
public class SausageStrategy implements MealStrategy { ... }

调节器

选项A:

@Resource(name = "burger")
MealStrategy burger;

@Resource(name = "sausage")
MealStrategy sausage;

@RequestMapping(method = RequestMethod.POST)
public @ResponseBody Something makeMeal(Meat meat) {
    burger.cookMeal(meat);
}

选项B:

@Autowired
BeanFactory bf;

@RequestMapping(method = RequestMethod.POST)
public @ResponseBody Something makeMeal(Meat meat) {
    bf.getBean("burger", MealStrategy.class).cookMeal(meat);
}

您可以选择创建JSR-330限定符而不是文本名称,以便在编译期间捕获拼写错误.

也可以看看:

如何有效地实施弹簧战略模式？

@Resource vs @Autowired