@Autowired：没有可用的 SpringBoot 应用程序类型的合格 bean

Question

I have an interface com.myapp.org.UsageRateLimiter defined in a library

public interface UsageRateLimiter {
  
  boolean tryAndConsume(String userId, String key, Long units);
}

I have a concrete class SlidingWindowRateLimiter :

@Component("slidingWindowRateLimiter")
public class SlidingWindowRateLimiter implements UsageRateLimiter {
  private final RateLimitingRedisProperties rateLimitingRedisProperties;

  public SlidingWindowRateLimiter(RateLimitingRedisProperties rateLimitingRedisProperties) {
    this.rateLimitingRedisProperties = rateLimitingRedisProperties;
  }

  @Override
  public boolean tryAndConsume(String userId, String key, Long units) {
    
    return true;
}

Another class com.myapp.org.RateLimitDriver had a reference to object of UsageRateLimiter type:

public class RateLimiterDriver {
  UsageRateLimiter rateLimiter;

  @Autowired
  RateLimiterDriver(UsageRateLimiter usageRateLimiter) {
    rateLimiter = usageRateLimiter;
  }

  public Decision getDecision(
      String userId, String key, BiFunction<String, String, Long> consumptionObject) {
    return rateLimiter.tryAndConsume(
            userId, key, consumptionObject.apply(userId, key))
        ? true
        : false;
  }
}

There are going to be other implementations of UsageRateLimiter as well with different Component names

Now in my controller class I need to instantiate RateLimiterDriver :

@RestController
@RequestMapping("/myApp/v1")
@Slf4j
public class MyappController implements MyappApi {

  @Autowired
  @Qualifier("slidingWindowRateLimiter")
  private RateLimiterDriver rateLimiterDriver;

  @Override
  public ResponseEntity<MyappResponse> createMyAppInstance(
      @RequestBody MyappPayload myAppPayload) {
    if (rateLimiterDriver.getDecision(userId, "create_my_app") == Decision.ALLOW) {
      return new ResponseEntity<>(HttpStatus.TOO_MANY_REQUESTS);
    }
  }
}

During deployment I am getting the below error:

No qualifying bean of type 'com.myapp.org.RateLimiterDriver' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true), @org.springframework.beans.factory.annotation.Qualifier(value="slidingWindowRateLimiter")}

Update : As I understand, the Qualifier ("slidingWindowRateLimiter") shouldn't be on the RateLimitDriver class but on the UsageLimiter class.

How can I pass on the correct UsageLimiter implementation from MyAppController using spring annotation? Sorry I'm new to spring boot, hence seeking help.

Answer 1

Finally I was able to come up with a solution using the fact that Spring provides the capability to collect all Beans which are concrete implementations of an interface into a Map

I modified my RateLimiterDriver class as:

@Component
public class RateLimiterDriver {
  @Value("${com.myapp.org.ratelimiter.type}")
  private String rateLimiterType;

  Map<String, UsageRateLimiter> rateLimiterTypeImplMap;

  @Autowired
  RateLimiterDriver(Map<String, UsageRateLimiter> rateLimiterTypeMap) {
    rateLimiterTypeImplMap = rateLimiterTypeMap;
  }

  public Decision getDecision(
      String userId, String key, BiFunction<String, String, Long> consumptionObject) {
    return rateLimiterTypeImplMap
            .get(rateLimiterType)
            .tryAndConsume(userId, key, consumptionObject.apply(userId, key))
        ? Decision.ALLOW
        : Decision.DROP;
  }
}

In my MyAppController , I am able to simply do

@Autowired RateLimiterDriver

and provide the bean name in the properties file:

com.myapp.org.ratelimiter.type=slidingWindowRateLimiter

Voila. Things working fine now. Thanks @timeofeevle for the suggestion.

Reference articles:

Dynamic autowire in Spring