Spring Boot - @Async

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Spring supports asynchronus processing using @Async annotaiton.

Enable Async Processing

To enable Scheduling annotation, add @EnableAsync to one of your @Configuration class.

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@Configuration
@EnableAsync
public class AsyncConfig {
  @Bean(name = "asyncExecutor")
  public Executor asyncExecutor()
  {
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(3);
    executor.setMaxPoolSize(3);
    executor.setQueueCapacity(100);
    executor.setThreadNamePrefix("AsynchThread-");
    executor.initialize();
    return executor;
  }
}

This class also create a customized Executor bean. If you don’t create a Executor bean. Spring by default will create a SimpleAsyncTaskExecutor bean.

@Async Annotation

@Async tells Spring that the method is asynchronous and should run on a separate thread.

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@Service
@Slf4j
public class SendMessageService {
  @Async( "asyncExecutor")
  public void sendMessage() {
      log.info(Thread.currentThread().getName() + " - sending message....");
  }
}

We can invoke the method to demonstrate it is executed asynchronously. The folowing controller calls the async method in its sendMessage() method.

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@RestController
@RequestMapping("/greeting")
@Slf4j
public class MyController {
  @Autowired
  SendMessageService sendMessageService;
  // GET localhost:8080/greeting/sendMessage
  @RequestMapping(value = "/sendMessage",
      method = RequestMethod.GET,
      produces = MediaType.APPLICATION_JSON_VALUE)
  public ResponseEntity<String> sendMessage() {
    sendMessageService.sendMessage();
    return ResponseEntity.status(HttpStatus.OK).body("Success");
  }
}

To test the method, we can invoke http://localhost:8080/greeting/sendMessage multiple times. We will see similar log output in the console. From the log, we know the method runs on asynchronous threads.

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AsynchThread-1 - sending message....
AsynchThread-2 - sending message....
AsynchThread-3 - sending message....
AsynchThread-1 - sending message....

Project files: https://github.com/xinghua24/SpringBootExamples/tree/master/async

Reference