2022-12-04

在使用ScheduledExecutorService进行周期性任务执行时，遇到一个问题：

1. 如果Runnable#run()方法抛异常的话，该异常会被ScheduledExecutorService吞掉，同时ScheduledExecutorService的周期性任务会被停掉。（如果ScheduledExecutorService有多个周期性任务的话，只有这个scheduleAtFixedRate()会被停掉，其它的可以正常执行）。

import java.util.Date;
import java.util.Locale;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class Demo {
    private final ScheduledExecutorService executorService = new ScheduledThreadPoolExecutor(3);
    private final Runnable runnable2 = () -> System.out.printf(Locale.CHINA, "[%s][%s]Runnable2 running...\n", new Date(), Thread.currentThread().getName());

    public static void main(String[] args) {
        Demo d = new Demo();
        d.test();
    }

    public void test() {
        executorService.scheduleAtFixedRate(this::executeRunnable1, 0, 1000, TimeUnit.MILLISECONDS);
        executorService.scheduleAtFixedRate(runnable2, 0, 2000, TimeUnit.MILLISECONDS);
    }

    private void executeRunnable1() {
        System.out.printf(Locale.CHINA, "[%s][%s]Runnable1 running...\n", new Date(), Thread.currentThread().getName());
        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        try {
            throw new RuntimeException("My Exception");
        } catch (Throwable t) { // Catch Throwable rather than Exception (a subclass).
            System.err.println(String.format(Locale.CHINA, "[%s][%s]%s\n", new Date(), Thread.currentThread().getName(), e));
        }
    }
}

Solution1:

最简单的Solution是在Runnable#run()方法中添加try-catch。

Solution2:

public void test() {
        ScheduledFuture<?> scheduledFuture1 = executorService.scheduleAtFixedRate(this::executeRunnable1, 0, 1000, TimeUnit.MILLISECONDS);
        try {
            //可以捕捉到java.lang.RuntimeException: My Exception错误，但是Runnable1不会持续执行。
            scheduledFuture1.get();
        } catch (InterruptedException | ExecutionException e) {
            e.printStackTrace();
        }
        executorService.scheduleAtFixedRate(runnable2, 0, 2000, TimeUnit.MILLISECONDS);
    }