Difference between @Bean and @Autowired

Question

Why can\'t I use @Autowired in this case?

@SpringBootApplication
public class Application {

    @Autowired
    BookingService bookingService;

         


        

Answer 1

Whatever class you have instantiated using @Autowire, you can instantiate it inside a class with @Configuration annotation using @Bean on the method.

Both @Autowire and @Bean are ways to initialize instances of a Class.

The difference is if you use @Bean to instantiate a class, you have more control over the initialization. For example if you are instantiating a Resilience4J Circuit breaker class, if you do it inside a method with @Bean, you have the option of setting all the config using code like this

@Bean
public CircuitBreaker fooCircuitBreaker() {
    CircuitBreakerConfig.Builder builder = CircuitBreakerConfig.custom().
            slidingWindowSize(xxx).
            failureRateThreshold(xxx).
            waitDurationInOpenState(xxx)).
            ignoreException(e -> {
                if (e instanceof HttpStatusCodeException) {
                    HttpStatusCodeException httpStatusCodeException = (HttpStatusCodeException) e;
                    if (httpStatusCodeException.getStatusCode().is4xxClientError()) {
                        return true;
                    }
                }
                return false;
            });
    circuitBreakerRegistry.addConfiguration(xxx, builder.build());
    return circuitBreakerRegistry.circuitBreaker(xxx, xxx);
}

In a case like this, using @Bean is obviously a better way.