SpringBoot 使用异步方法
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;}@Overridepublic 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();}@Asyncpublic 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 purposesThread.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);}@Overridepublic 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;}@Overridepublic void run(String... args) throws Exception {// Start the clocklong start = System.currentTimeMillis();// Kick of multiple, asynchronous lookupsFuture<User> page1 = gitHubLookupService.findUser("PivotalSoftware");Future<User> page2 = gitHubLookupService.findUser("CloudFoundry");Future<User> page3 = gitHubLookupService.findUser("Spring-Projects");// Wait until they are all donewhile (!(page1.isDone() && page2.isDone() && page3.isDone())) {Thread.sleep(10); //10-millisecond pause between each check}// Print results, including elapsed timelogger.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。
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