How to Autowire a Spring-annotated service class in a @Configuration class?

Question

I'm trying to inject a service-annotated class into a configuration class in a Spring Boot application, but it doesn't get injected (is set to null), which I assume is due to the Spring lifeycle.

Also, this service has an overloaded constructor that uses constructor injection, and I guess this is also a problem, as autowiring acts upon a default constructor. However, the service needs to be Spring-configured, so I don't think one can create a new instance in a Bean annotated method.

How can one solve this?

@Configuration
@Order(SecurityProperties.ACCESS_OVERRIDE_ORDER)
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {

    @Autowired
    private SessionService sessionService;

    @Bean
    public SessionService sessionService() {
        return sessionService;
    }
}

public interface SessionService extends BaseCacheService<Session> {
    void extendExpiration(String key);

    String getSessionId(String key);
}

@Service
public class SessionServiceImpl implements SessionService {

    private Environment environment;
    private UserService userService;

    @Autowired
    public SessionServiceImpl(Environment environment, UserService userService) {
      this.environment = environment;
      this.userService = userService;
    }
}

If I exclude the @Bean method, then I get a compilation error:

Answer 1

Your error is the following (you are returning a null value):

@Bean
public SessionService sessionService() {
    return sessionService;
}

---

Solution

1. Since your SessionServiceImpl is annotated with @Service, you can just remove the @Bean method and let spring create it. Spring already makes it available for you.

2. Or, If your SessionServiceImpl wasn't annotated with @Service, you would need the following :

@Bean
public SessionService sessionService() {
   return new SessionService();
}

---

If this doesn't work, it may just be that your SessionServiceImpl is in a package not being scanned by spring (as suggested by @Miloš Milivojević)

You may add @ComponentScan to your Configuration class

@Configuration
@Order(SecurityProperties.ACCESS_OVERRIDE_ORDER)
@ComponentScan("com.package.to.sessionServiceImpl-or-higher")
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {