一、新建项目，启动异步调用

首先给启动类增加注解@EnableAsync，支持异步调用

(资料图)

@EnableAsync@SpringBootApplicationpublic class CathySpringbootDemoApplication {    public static void main(String[] args) {        SpringApplication.run(CathySpringbootDemoApplication.class, args);    }}

然后定义要执行的Task，分类增加一个同步方法和异步方法，其中异步方法需要增加注解@Async

@Componentpublic class AsyncTask {    /**     * 异步任务，需要注解@Async     *     * @param taskId 任务编号id     * @param second 执行时长，模拟慢任务     * @return     */    @Async    public Future asyncExec(int taskId, Long second) {        exec(taskId, second);        return new AsyncResult<>(Boolean.TRUE);    }    public void exec(int taskId, Long second) {        System.out.println("开始执行任务" + taskId);        try {            Thread.sleep(second * 1000);        } catch (InterruptedException e) {            throw new RuntimeException(e);        }        System.out.println("结束执行任务" + taskId);    }}

其实接下来就可以在controller中创建接口来进行简单的测试了

@RestController@RequestMapping("/async")public class AsyncController {    @Autowired    AsyncTask asyncTask;    @GetMapping("sync_task")    public String syncTask() {        long start = System.currentTimeMillis();        asyncTask.exec(1, 3L);        asyncTask.exec(2, 3L);        asyncTask.exec(3, 3L);        long time = System.currentTimeMillis() - start;        return "同步执行，耗时" + time;    }    @GetMapping("async_task")    public String asyncTask() {        long start = System.currentTimeMillis();        Future f1 = asyncTask.asyncExec(1, 3L);        Future f2 = asyncTask.asyncExec(2, 3L);        Future f3 = asyncTask.asyncExec(3, 3L);        try {            f1.get();            f2.get();            f3.get();        } catch (InterruptedException e) {            throw new RuntimeException(e);        } catch (ExecutionException e) {            throw new RuntimeException(e);        }        long time = System.currentTimeMillis() - start;        return "异步执行，耗时" + time;    }}

启动程序，查看接口响应结果：http://localhost:16001/async/sync_task

http://localhost:16001/async/async_task

注意：异步方法和调用一定要写在不同的类中

二、线程池配置

上面的例子，在耗时服务多的情况下，使用异步方法确实提高了响应速度。但是它默认启用的是Spring默认的线程池SimpleAsyncTaskExecutor，不太灵活。我们把异步请求多增加几次调用看看效果：

@GetMapping("async_task")    public String asyncTask() {        long start = System.currentTimeMillis();        List> list = new ArrayList<>();        for (int i = 0; i < 20; i++) {            Future fi = asyncTask.asyncExec(i, 10L);            list.add(fi);        }        for (int i = 0; i < 20; i++) {            list.forEach(x -> {                try {                    x.get();                } catch (InterruptedException e) {                    throw new RuntimeException(e);                } catch (ExecutionException e) {                    throw new RuntimeException(e);                }            });        }        long time = System.currentTimeMillis() - start;        return "异步执行，耗时" + time;    }

从上面的运行效果来看，一旦超过8个并行执行的任务，就开始出现等待了。

接下来，我们自定义线程池

@Bean public TaskExecutor threadPoolTaskExecutor(){     ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();     executor.setCorePoolSize(8);     executor.setMaxPoolSize(16);     executor.setQueueCapacity(20);     executor.setKeepAliveSeconds(30);     executor.setWaitForTasksToCompleteOnShutdown(true);     executor.setThreadNamePrefix("task-thread-");     executor.setRejectedExecutionHandler(new ThreadPoolExecutor.DiscardOldestPolicy());     executor.initialize();     return executor; }

然后在异步方法的注解中，明确指定所使用的线程池

@Async("threadPoolTaskExecutor")    public Future asyncExec(int taskId, Long second) {        exec(taskId, second);        return new AsyncResult<>(Boolean.TRUE);    }

执行效果如下：

可以看出，线程池设置的参数已经生效。