原来你是这样的SpringBoot--Async异步任务
本节我们一起学习一下SpringBoot中的异步调用，主要用于优化耗时较长的操作，提高系统性能和吞吐量。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
@EnableAsync
@SpringBootApplication
public 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
@Component
public 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<Boolean> 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<Boolean> f1 = asyncTask.asyncExec(1, 3L);
Future<Boolean> f2 = asyncTask.asyncExec(2, 3L);
Future<Boolean> 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
https://img2023.cnblogs.com/blog/37001/202308/37001-20230822162534731-235767734.png
http://localhost:16001/async/async_task
https://img2023.cnblogs.com/blog/37001/202308/37001-20230822162604609-1033011007.png
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<Future<Boolean>> list = new ArrayList<>();
for (int i = 0; i < 20; i++) {
Future<Boolean> 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;
}https://img2023.cnblogs.com/blog/37001/202308/37001-20230822164547506-615559233.png
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<Boolean> asyncExec(int taskId, Long second) {
exec(taskId, second);
return new AsyncResult<>(Boolean.TRUE);
}执行效果如下：
https://img2023.cnblogs.com/blog/37001/202308/37001-20230822173944316-1626972881.png
https://img2023.cnblogs.com/blog/37001/202308/37001-20230823093142199-36114177.png
可以看出，线程池设置的参数已经生效。
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https://img2023.cnblogs.com/blog/37001/202308/37001-20230822194405666-261743903.jpg
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