调用 SuperClass 中的服务，其实现注入到子类中

Question

我在 JavaSE 应用程序中使用 Weld for Cdi。
我的一些服务有两种形式。通过 Qualifier（@Italian 或 @Chinese）在 CDI 中进行区分。大多数服务代码位于共享超类中。
这个超类使用其他服务。具有共同实现的那些被简单地注入到超类中（TimerService）。但是如果有具体的实现，就要看子类选择哪个实现了。
在下面的示例中：当 ItalianFoodController 调用 service.cookSoup() 时，它应该使用意大利汤食谱...

public abstract class FoodService {
    @Inject TimerService timerService;

    abstract protected RecipeService getRecipeService();

    protected void cookSoup() {
        getRecipeService().getSoupRecipe();
        timerService.setTimer(20);
        ...
    }
}

@ApplicationScoped @Italian
public class ItalianFoodService extends FoodService {
    @Inject @Italian RecipeService recipeService;

    @Override
    protected RecipeService getRecipeService() {
        return recipeService;
    }
    ...
}

@ApplicationScoped @Chinese
public class ChineseFoodService extends FoodService {
    @Inject @Chinese RecipeService recipeService;
    ...
}

public class ItalianFoodController {
    @Inject @Italian ItalianFoodService service;
    ...
    public void cook() {
        service.cookSoup();
    }
}

示例运行良好。
我的问题是：是否有 CDI 模式可以摆脱 getRecipeService()？
最直观的方法是：

public abstract class FoodService {
    @Inject RecipeService recipeService;
    ...    
}
public class ItalianFoodService extends FoodService {
    @Inject @Italian RecipeService recipeService;
    ...    
}

但这不起作用，因为 recipeService 将被隐藏但不会被子类覆盖。

Answer 1

是的，有，叫做Instance.select(qualifier)。这就是它的工作原理：

public abstract class FoodService {

    @Inject
    TimerService timerService;

    @Any
    @Inject
    Instance<RecipeService> recipeServices;

    private final Annotation recipeSelector;

    FoodService(){
        //this is just one way you can get hold of the qualifier for each soup service
        // another way is to look into AnnotationLiteral
        recipeSelector = Arrays.stream(getClass().getDeclaredAnnotations())
        .filter((ann) -> annot.annotationType().isAnnotationPresent(Qualfiier.class))
        .findFirst()
        .orElseThrow(()-> new someexception());
    }

    protected void cookSoup() {
        RecipeService service = recipeServices.select(recipeSelector).get().getSoupRecipe();
        timerService.setTimer(20);
    }
}

有关此的更多详细信息： http://docs.jboss.org/cdi/spec/2.0/cdi-spec.html#dynamic_lookup 和 http://docs.jboss.org/cdi/spec/2.0/cdi-spec.html#annotationliteral_typeliteral

Answer 2

考虑到@maress 的回答，我想到了一种不同的方法，它允许我非常直观地使用注入的服务。

使用构造函数注入的解决方案：

public abstract class FoodService {
    protected RecipeService recipeService;

    FoodService (RecipeService recipeService) {
        this.recipeService = recipeService;
    }
}

public class ItalianFoodService extends FoodService {
    // Only needed if ItalianRecipeService holds additional methods.
    @Inject @Italian ItalianRecipeService recipeService;

    @Inject
    ItalianFoodService(@Italian RecipeService recipeService) {
       super(recipeService);
    }
}

也可以通过

实现同样的效果

使用@PostConstruct的解决方案：

public abstract class FoodService {
    protected RecipeService recipeService;
}

public class ItalianFoodService extends FoodService {
    // Only needed if ItalianRecipeService holds additional methods.
    @Inject @Italian ItalianRecipeService recipeService;

    @PostConstruct
    postConstruct() {
       super.recipeService = recipeService;
    }
}

两种解决方案都非常简短且可读性强，而带有构造函数注入的解决方案对注入的解释更为明确。

调用 SuperClass 中的服务，其实现注入到子类中

Call a service in SuperClass whose implementation is injected in subclass

java

inheritance

cdi

weld