Spring @Async and @EnableAsync annotation Example

Spring @Async and @EnableAsync annotation example

@EnableAsync annotation

Make the Application Executable, The @EnableAsync annotation switches on Spring’s ability to run @Async methods in a background thread pool. This class also customizes the Executor by defining a new bean.

Spring’s @Async annotation works with web applications, but you need not set up a web container to see its benefits.

The following listing (from src/main/java/com/example/asyncmethod/AsyncMethodApplication.java) shows how to do so:

package com.example.asyncmethod;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.scheduling.concurrent.ThreadPoolTaskExecutor;

import java.util.concurrent.Executor;

@SpringBootApplication
@EnableAsync
public class AsyncMethodApplication {

  public static void main(String[] args) {
    // close the application context to shut down the custom ExecutorService
    SpringApplication.run(AsyncMethodApplication.class, args).close();
  }

  @Bean
  public Executor taskExecutor() {
    ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(2);
    executor.setMaxPoolSize(2);
    executor.setQueueCapacity(500);
    executor.setThreadNamePrefix("GithubLookup-");
    executor.initialize();
    return executor;
  }
}

@Async annotation

Spring’s @Async annotation, indicating that it should run on a separate thread.

Next, you need to create a service that queries to find user information. The following listing (from src/main/java/com/example/asyncmethod/GitHubLookupService.java) shows how to do so:

package com.example.asyncmethod;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.web.client.RestTemplateBuilder;
import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

import java.util.concurrent.CompletableFuture;

@Service
public class GitHubLookupService {

  private static final Logger logger = LoggerFactory.getLogger(GitHubLookupService.class);

  private final RestTemplate restTemplate;

  public GitHubLookupService(RestTemplateBuilder restTemplateBuilder) {
    this.restTemplate = restTemplateBuilder.build();
  }

  @Async
  public CompletableFuture<User> findUser(String user) throws InterruptedException {
    logger.info("Looking up " + user);
    String url = String.format("https://api.github.com/users/%s", user);
    User results = restTemplate.getForObject(url, User.class);
    // Artificial delay of 1s for demonstration purposes
    Thread.sleep(1000L);
    return CompletableFuture.completedFuture(results);
  }

}