SpringBoot中如何优雅的使用多线程

news2024/10/9 18:20:20

本文带你快速了解@Async注解的用法，包括异步方法无返回值、有返回值，最后总结了@Async注解失效的几个坑。

在 SpringBoot 应用中，经常会遇到在一个接口中，同时做事情1，事情2，事情3，如果同步执行的话，则本次接口时间取决于事情1 2 3执行时间之和；如果三件事同时执行，则本次接口时间取决于事情1 2 3执行时间最长的那个，合理使用多线程，可以大大缩短接口时间。那么在 SpringBoot 应用中如何优雅的使用多线程呢？

Don't bb, show me code.

快速使用

SpringBoot应用中需要添加@EnableAsync注解，来开启异步调用，一般还会配置一个线程池，异步的方法交给特定的线程池完成，如下：

@Configuration
@EnableAsync
public class AsyncConfiguration {

    @Bean("doSomethingExecutor")
    public Executor doSomethingExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        // 核心线程数：线程池创建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核心线程数的线程
        executor.setMaxPoolSize(20);
        // 缓冲队列：用来缓冲执行任务的队列
        executor.setQueueCapacity(500);
        // 允许线程的空闲时间60秒：当超过了核心线程之外的线程在空闲时间到达之后会被销毁
        executor.setKeepAliveSeconds(60);
        // 线程池名的前缀：设置好了之后可以方便我们定位处理任务所在的线程池
        executor.setThreadNamePrefix("do-something-");
        // 缓冲队列满了之后的拒绝策略：由调用线程处理（一般是主线程）
        executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardPolicy());
        executor.initialize();
        return executor;
    }

}

使用的方式非常简单，在需要异步的方法上加@Async注解

@RestController
public 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";
    }
}


@Slf4j
@Service
public class AsyncService {

    // 指定使用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;
    }
}

访问：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

由此可见已经达到异步执行的效果了，并且使用到了咱们配置的线程池。

获取异步方法返回值

当异步方法有返回值时，如何获取异步方法执行的返回结果呢？这时需要异步调用的方法带有返回值CompletableFuture。

CompletableFuture是对Feature的增强，Feature只能处理简单的异步任务，而CompletableFuture可以将多个异步任务进行复杂的组合。如下：

@RestController
public class AsyncController {

    @Autowired
    private AsyncService asyncService;

    @SneakyThrows
    @ApiOperation("异步 有返回值")
    @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");

        // 等待所有任务都执行完
        CompletableFuture.allOf(createOrder, reduceAccount, saveLog).join();
        // 获取每个任务的返回结果
        String result = createOrder.get() + reduceAccount.get() + saveLog.get();
        return result;
    }
}


@Slf4j
@Service
public 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);
    }
}

访问接口

C:\Users\Administrator>curl -X GET "http://localhost:8200/open/somethings" -H "accept: */*"
do something1: create order; do something2: reduce account; do something3: save log

控制台上关键日志如下：

2020-04-20 00:27:42.238  INFO 5672 --- [ do-something-3] x.gits.boot.system.service.AsyncService  : do something3: save log
2020-04-20 00:27:42.238  INFO 5672 --- [ do-something-2] x.gits.boot.system.service.AsyncService  : do something2: reduce account
2020-04-20 00:27:42.238  INFO 5672 --- [ do-something-1] x.gits.boot.system.service.AsyncService  : do something1: create order