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：

 

<dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter</artifactId>

        </dependency>

 

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-web</artifactId>

        </dependency>

        <dependency>

            <groupId>com.fasterxml.jackson.core</groupId>

            <artifactId>jackson-databind</artifactId>

        </dependency>

 

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:

 

@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 Future<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 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

@EnableAsync

public 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：

 

@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

        Future<User> page1 = gitHubLookupService.findUser("PivotalSoftware");

        Future<User> page2 = gitHubLookupService.findUser("CloudFoundry");

        Future<User> 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。