Strategy pattern with spring beans

Question

Say I\'m using spring, I have the following strategies...

Interface

public interface MealStrategy {
    cook(Meat meat);
}

First st

Answer 1

I would use simple Dependency Injection.

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

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

Controller

Option A:

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

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

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

Option B:

@Autowired
BeanFactory bf;

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

You can choose to create JSR-330 qualifiers instead of textual names to catch misspellings during compile time.

See also:

How to efficiently implement a strategy pattern with spring?

@Resource vs @Autowired

Answer 2

Since a concrete strategy is very often determined at run time based on the provided parameters or so, I would suggest something as follows.

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

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

Then inject all such strategies into a map (with bean name as a key) in the given controller and select respective strategy on request.

@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);

    ...
}