SpringBoot非官方教程 | 第二十三篇： 异步方法

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http://blog.csdn.net/forezp/article/details/71024169
本文出自方志朋的博客

这篇文章主要介绍在springboot 使用异步方法，去请求github api.

创建工程

在pom文件引入相关依赖：

            org.springframework.boot            spring-boot-starter            org.springframework            spring-web            com.fasterxml.jackson.core            jackson-databind

创建一个接收数据的实体：

@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 + "]";    }}

创建一个请求的　githib的service:

@Servicepublic 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 Future 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 new AsyncResult<>(results);    }}

通过，RestTemplate去请求，另外加上类@Async 表明是一个异步任务。

开启异步任务：

@SpringBootApplication@EnableAsyncpublic class Application extends AsyncConfigurerSupport {    public static void main(String[] args) {        SpringApplication.run(Application.class, args);    }    @Override    public Executor getAsyncExecutor() {        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();        executor.setCorePoolSize(2);        executor.setMaxPoolSize(2);        executor.setQueueCapacity(500);        executor.setThreadNamePrefix("GithubLookup-");        executor.initialize();        return executor;    }}

通过@EnableAsync开启异步任务；并且配置AsyncConfigurerSupport，比如最大的线程池为2.

测试

测试代码如下：

@Componentpublic 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        Future page1 = gitHubLookupService.findUser("PivotalSoftware");        Future page2 = gitHubLookupService.findUser("CloudFoundry");        Future page3 = gitHubLookupService.findUser("Spring-Projects");        // Wait until they are all done        while (!(page1.isDone() && page2.isDone() && page3.isDone())) {            Thread.sleep(10); //10-millisecond pause between each check        }        // Print results, including elapsed time        logger.info("Elapsed time: " + (System.currentTimeMillis() - start));        logger.info("--> " + page1.get());        logger.info("--> " + page2.get());        logger.info("--> " + page3.get());    }}

启动程序，控制台会打印：

2017-04-30 13:11:10.351 INFO 1511 — [ GithubLookup-1] com.forezp.service.GitHubLookupService : Looking up PivotalSoftware
2017-04-30 13:11:10.351 INFO 1511 — [ GithubLookup-2] com.forezp.service.GitHubLookupService : Looking up CloudFoundry
2017-04-30 13:11:13.144 INFO 1511 — [ GithubLookup-2] com.forezp.service.GitHubLookupService : Looking up spring-Projects

耗时：3908

分析：可以卡的前面2个方法分别在GithubLookup-1 和GithubLookup-2执行，第三个在GithubLookup-2执行，注意因为在配置线程池的时候最大线程为2.如果你把线程池的个数为3的时候，耗时减少。

如果去掉@Async，你会发现，执行这三个方法都在main线程中执行。耗时总结，如下：

2017-04-30 13:13:00.934 INFO 1527 — [ main] com.forezp.service.GitHubLookupService : Looking up PivotalSoftware
2017-04-30 13:13:03.571 INFO 1527 — [ main] com.forezp.service.GitHubLookupService : Looking up CloudFoundry
2017-04-30 13:13:04.865 INFO 1527 — [ main] com.forezp.service.GitHubLookupService : Looking up Spring-Projects

耗时：5261

通过这一个小的栗子，你应该对异步任务有了一定的了解。

参考资料

https://spring.io/guides/gs/async-method/

源码下载

https://github.com/forezp/SpringBootLearning

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