Is this design of Spring singleton beans thread safe?

Question

Consider the following Spring Service class. The spring scope defined is Singleton. The two service beans auto-wired as fields in the class below have similar structure - they too are composed of fields which are either of the following

Spring beans themselves
stateless classes
immutable classes

and so on. This pattern is overall used in the application design.

@Service     
public class DocumentService {  
  private final DocumentGenerationService documentGenerationService;
  private final DocumentPublishService documentPublishService;

  @Autowired
  public DocumentService (DocumentGenerationService documentGenerationService,    
                          DocumentPublishService documentPublishService) {
  this.documentGenerationService = documentGenerationService;
  this.documentPublishService = documentPublishService;
}

... methods follow

Is it correct to say that the DocumentService class is immutable since it's not possible to mutate any of its two fields (which are spring beans that can be initialized only once by the container itself)?

In any case, can the DocumentService bean as defined above be considered thread-safe? And if this design is followed the application as a whole is thread-safe too?

Is this design of Spring singleton beans thread safe?

6 Answers