关于java:SpringBoot中如何优雅的使用多线程

在 SpringBoot 利用中，常常会遇到在一个接口中，同时做事件1，事件2，事件3，如果同步执行的话，则本次接口工夫取决于事件1 2 3执行工夫之和；如果三件事同时执行，则本次接口工夫取决于事件1 2 3执行工夫最长的那个，正当应用多线程，能够大大缩短接口工夫。那么在 SpringBoot 利用中如何优雅的应用多线程呢？

疾速应用
SpringBoot利用中须要增加@EnableAsync注解，来开启异步调用，个别还会配置一个线程池，异步的办法交给特定的线程池实现，如下：

@Configuration@EnableAsyncpublic class AsyncConfiguration {    @Bean("doSomethingExecutor")    public Executor doSomethingExecutor() {        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();        // 外围线程数：线程池创立时候初始化的线程数        executor.setCorePoolSize(10);        // 最大线程数：线程池最大的线程数，只有在缓冲队列满了之后才会申请超过外围线程数的线程        executor.setMaxPoolSize(20);        // 缓冲队列：用来缓冲执行工作的队列        executor.setQueueCapacity(500);        // 容许线程的闲暇工夫60秒：当超过了外围线程之外的线程在闲暇工夫达到之后会被销毁        executor.setKeepAliveSeconds(60);        // 线程池名的前缀：设置好了之后能够不便咱们定位解决工作所在的线程池        executor.setThreadNamePrefix("do-something-");        // 缓冲队列满了之后的回绝策略：由调用线程解决（个别是主线程）        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());        executor.initialize();        return executor;    }}

AsyncService

@Slf4j@Servicepublic class AsyncService {    // 指定应用beanname为doSomethingExecutor的线程池    @Async("doSomethingExecutor")    public String doSomething(String message) {        log.info("do something, message={}", message);        try {            Thread.sleep(1000);        } catch (InterruptedException e) {            log.error("do something error: ", e);        }        return message;    }}

AsyncController

@RestControllerpublic class AsyncController {    @Autowired    private AsyncService asyncService;    @GetMapping("/open/something")    public String something() {        int count = 10;        for (int i = 0; i < count; i++) {            asyncService.doSomething("index = " + i);        }        lon        return "success";    }}

拜访：127.0.0.1:8080/open/something，日志如下

2020-04-19 23:42:42.486 INFO 21168 — [io-8200-exec-17] x.g.b.system.controller.AsyncController : do something end, time 8 milliseconds
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-1] x.gits.boot.system.service.AsyncService : do something, message=index = 0
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-5] x.gits.boot.system.service.AsyncService : do something, message=index = 4
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-4] x.gits.boot.system.service.AsyncService : do something, message=index = 3
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-6] x.gits.boot.system.service.AsyncService : do something, message=index = 5
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-9] x.gits.boot.system.service.AsyncService : do something, message=index = 8
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-8] x.gits.boot.system.service.AsyncService : do something, message=index = 7
2020-04-19 23:42:42.488 INFO 21168 — [do-something-10] x.gits.boot.system.service.AsyncService : do something, message=index = 9
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-7] x.gits.boot.system.service.AsyncService : do something, message=index = 6
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-2] x.gits.boot.system.service.AsyncService : do something, message=index = 1
2020-04-19 23:42:42.488 INFO 21168 — [ do-something-3] x.gits.boot.system.service.AsyncService : do something, message=index = 2

由此可见曾经达到异步执行的成果了，并且应用到了咱们配置的线程池

获取异步办法返回值

当异步办法有返回值时，如何获取异步办法执行的返回后果呢？这时须要异步调用的办法带有返回值CompletableFuture。
CompletableFuture是对Feature的加强，Feature只能解决简略的异步工作，而CompletableFuture能够将多个异步工作进行简单的组合。如下：

AsyncService

@Slf4j@Servicepublic class AsyncService {    @Async("doSomethingExecutor")    public CompletableFuture<String> doSomething1(String message) throws InterruptedException {        log.info("do something1: {}", message);        Thread.sleep(1000);        return CompletableFuture.completedFuture("do something1: " + message);    }    @Async("doSomethingExecutor")    public CompletableFuture<String> doSomething2(String message) throws InterruptedException {        log.info("do something2: {}", message);        Thread.sleep(1000);        return CompletableFuture.completedFuture("; do something2: " + message);    }    @Async("doSomethingExecutor")    public CompletableFuture<String> doSomething3(String message) throws InterruptedException {        log.info("do something3: {}", message);        Thread.sleep(1000);        return CompletableFuture.completedFuture("; do something3: " + message);    }}

AsyncController

@RestControllerpublic class AsyncController {    @Autowired    private AsyncService asyncService;    @GetMapping("/open/somethings")    public String somethings() {        CompletableFuture<String> createOrder = asyncService.doSomething1("create order");        CompletableFuture<String> reduceAccount = asyncService.doSomething2("reduce account");        CompletableFuture<String> saveLog = asyncService.doSomething3("save log");        // 期待所有工作都执行完        CompletableFuture.allOf(createOrder, reduceAccount, saveLog).join();        // 获取每个工作的返回后果        String result = createOrder.get() + reduceAccount.get() + saveLog.get();        return result;    }}

注意事项

@Async注解会在以下几个场景生效，也就是说明明应用了@Async注解，但就没有走多线程

1.异步办法应用static关键词润饰
2.异步类不是一个Spring容器的bean（个别应用注解@Component和@Service，并且能被Spring扫描到）
3.SpringBoot利用中没有增加@EnableAsync注解
4.在同一个类中，一个办法调用另外一个有@Async注解的办法，注解不会失效。起因是@Async注解的办法，是在代理类中执行的