AsyncConfigurerSupport 自定义异步线程池

一、AsyncConfigurerSupport 简介

spring 中开启异步只要在配置类加上
@EnableAsync 同时在service方法中加上@Async即可，注意service中的方法想要异步调用必须是通过注入调用(spring 代理)。

@Service
public class ServiceA{
   public void testA(){
       testB();
   }

   @Async
   public void testB(){

   }
}

上述方法在调用testA时是同步调用，而非异步调用，方法内部的直接调用是没有经过spring 代理的。

二、自定义异步调用的线程池和异常处理

AsyncConfigurerSupport 只定义了两个方法分别用于自定义异步线程池、异步产生的异常捕获，通过实现此类即可实现自定义的异步线程池。

demo如下:

新建子类 AsyncConfigHandler

@Configuration
@EnableAsync
public class AsyncConfigHandler extends AsyncConfigurerSupport {

    @Override
    public Executor getAsyncExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(5);
        executor.setMaxPoolSize(10);
        executor.setQueueCapacity(10);
        executor.initialize();
        return executor;
    }

    @Override
    public AsyncUncaughtExceptionHandler getAsyncUncaughtExceptionHandler() {
        return new MyAsyncUncaughtExceptionHandler();
    }

    @Bean   // /actuator/shutdown
    @Override
    public Executor getAsyncExecutor2() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setTaskDecorator(new SomeTaskDecorator());
        executor.setCorePoolSize(4);
        executor.setMaxPoolSize(8);
        executor.setQueueCapacity(100);
        executor.setAllowCoreThreadTimeOut(false);
        executor.setKeepAliveSeconds(0);
        executor.setThreadNamePrefix("DefaultAsync-");
        executor.setWaitForTasksToCompleteOnShutdown(true); // 다 끝날때까지 대기
        executor.initialize();
        return executor;
    }

    static class SomeTaskDecorator implements TaskDecorator {
        @Override
        public Runnable decorate(Runnable runnable) {
            return () -> {
                try {
                    log.info("Some Task Decorator Start");
                    runnable.run();
                } finally {
                    log.info("Some Task Decorator End");
                }
            };
        }
    }
}

class MyAsyncUncaughtExceptionHandler implements AsyncUncaughtExceptionHandler {
    @Override
    public void handleUncaughtException(Throwable ex, Method method, Object... params) {
        System.out.println("class#method: " + method.getDeclaringClass().getName() + "#" + method.getName());
        System.out.println("type        : " + ex.getClass().getName());
        System.out.println("exception   : " + ex.getMessage());
    }
}

编写支持异步调用注解@Async的 DemoService

@Service
public class DemoService {

    @Async
    public void testAsync() throws InterruptedException {
        System.out.println("这里是异步方法");
        TimeUnit.SECONDS.sleep(10);
        int i = 1 / 0;
    }
}

编写测试 controller

@RestController
@RequestMapping(value = "time")
public class DemoController {

    @Autowired
    private DemoService demoService;

    @RequestMapping(value = "getTimeAndAsync")
    public String getTimeAndAsync() throws InterruptedException {
        demoService.testAsync();
        return "异步加载=》" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
    }
}

新建spring boot应用的步骤省略

访问 http://localhost:8080/time/getTimeAndAsync

浏览器会立即输出

异步加载=》2021-02-20 15:56:16

等待十秒钟后会捕获异常

class#method: com.example.bootdemo.service.DemoService#testAsync
type : java.lang.ArithmeticException
exception : / by zero

同步调用中可以采用 @RestControllerAdvice 和 @ExceptionHandler 注解捕获全局的异常然后进行处理，如果是异步调用则需要实现 AsyncUncaughtExceptionHandler 进行单独的额外处理。