【并发】基于 @Async和 CompletableFuture 实现并发异步操作

参考链接：Spring官方示例

User.java

package hello;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;

@JsonIgnoreProperties(ignoreUnknown=true)
public class User {

private String name;
private String blog;

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public String getBlog() {
return blog;
}

public void setBlog(String blog) {
this.blog = blog;
}

@Override
public String toString() {
return "User [name=" + name + ", blog=" + blog + "]";
}

}

@Async

添加 @Async注解；

返回值声明为： CompletableFuture

配置 @Component 或 @ Service 等，保证可以 组件扫描到

package hello;

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);
}

}

自定义 Executor（可选）,并开启注解 @EnableAsync

如果不配置，则使用默认的：SimpleAsyncTaskExecutor

package hello;

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 Application {

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

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

}

获取并发执行结果

package hello;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;

import java.util.concurrent.CompletableFuture;

@Component
public class AppRunner implements CommandLineRunner {

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

private final GitHubLookupService gitHubLookupService;

public AppRunner(GitHubLookupService gitHubLookupService) {
this.gitHubLookupService = gitHubLookupService;
}

@Override
public void run(String... args) throws Exception {
// Start the clock
long start = System.currentTimeMillis();

// Kick of multiple, asynchronous lookups
CompletableFuture<User> page1 = gitHubLookupService.findUser("PivotalSoftware");
CompletableFuture<User> page2 = gitHubLookupService.findUser("CloudFoundry");
CompletableFuture<User> page3 = gitHubLookupService.findUser("Spring-Projects");

// Wait until they are all done
CompletableFuture.allOf(page1,page2,page3).join();

// Print results, including elapsed time
logger.info("Elapsed time: " + (System.currentTimeMillis() - start));
logger.info("--> " + page1.get());
logger.info("--> " + page2.get());
logger.info("--> " + page3.get());

}

}

结果

2016-09-01 10:25:21.295  INFO 17893 --- [ GithubLookup-2] hello.GitHubLookupService                : Looking up CloudFoundry
2016-09-01 10:25:21.295  INFO 17893 --- [ GithubLookup-1] hello.GitHubLookupService                : Looking up PivotalSoftware
2016-09-01 10:25:23.142  INFO 17893 --- [ GithubLookup-1] hello.GitHubLookupService                : Looking up Spring-Projects
2016-09-01 10:25:24.281  INFO 17893 --- [           main] hello.AppRunner                          : Elapsed time: 2994
2016-09-01 10:25:24.282  INFO 17893 --- [           main] hello.AppRunner                          : --> User [name=Pivotal Software, Inc., blog=http://pivotal.io]
2016-09-01 10:25:24.282  INFO 17893 --- [           main] hello.AppRunner                          : --> User [name=Cloud Foundry, blog=https://www.cloudfoundry.org/]
2016-09-01 10:25:24.282  INFO 17893 --- [           main] hello.AppRunner                          : --> User [name=Spring, blog=http://spring.io/projects]