@Async giving me error in spring boot application

Question

This is main application class:

@EnableAsync(proxyTargetClass = true)
@EnableDiscoveryClient
@SpringBootApplication
public class ProductApplication {

    public static void main(final String[] args) {
        SpringApplication.run(ProductApplication.class, args);
    }

    @Bean("threadPoolTaskExecutor")
    public TaskExecutor getAsyncExecutor() {
        final ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(20);
        executor.setMaxPoolSize(1000);
        executor.setWaitForTasksToCompleteOnShutdown(true);
        executor.setThreadNamePrefix("Async-");
        return executor;
    }

}

This is service class:

@Component
public class ProductServiceImpl implements ProductService {

    @Autowired
    ProductRepository productRepository;

    @Autowired
    private ProductHandler productHandler;

    @Async
    @Override
    public List<String> getAllCategories() {
        final List<String> finalList = new ArrayList<>();
        return finalList;
    }

}

This is the controller class:

@RestController
public class ProductResource {

    @Autowired
    private ProductServiceImpl productServiceImpl;

    @GetMapping("/categories")
    public ResponseEntity<List<String>> getAllCategories() {
        return new ResponseEntity<>(this.productServiceImpl.getAllCategories(), HttpStatus.OK);
    }
}

I have annotated the service implementation method with @Async but I get this error:

Action:

Consider injecting the bean as one of its interfaces or forcing the use of CGLib-based proxies by setting proxyTargetClass=true on @EnableAsync and/or @EnableCaching.

If I try annotating the controller I get empty response to my get request. I have try every thing including setting proxyTargetClass to true.

Either ditch your ProductService interface or start using it by using ProductService instead of ProductserviceImpl in your controller. — M. Deinum
@M.Deinum Could you please tell me why I can't apply async to ProductserviceImpl? — pawan
I nowhere said that. I said you should be either be programming to interface (use the interface instead of the implementation in your controller) or ditch the interface all together. — M. Deinum
I autowired ProductService. I got empty response, but when I removed @Async annotation I got the response. Could you tell me how to fix it? — pawan

Nikolas Charalambidis Nikolas Charalambidis · Accepted Answer · 2020-04-10T14:08:59

As long as you use @Async annotation, you have to get familiar with the rules that have to be respected while using it:

The method must be public only
It cannot be called from a method within the same class (self-invocation)
If a return type is used, it has to be wrapped in Future<T>, ex. CompletableFuture<T>

So you get:

CompletableFuture<List<String>> categories = this.productServiceImpl.getAllCategories();

The further handling is driven by the implementation of Future where you can either block the execution or join more of them into a single response...

@Async giving me error in spring boot application

1 Answers