java - 停止已经运行的线程

Question

我有两个 API:一个启动线程，另一个停止线程。我可以通过调用 /start API 成功地启动一个线程，但是我无法通过调用 /stop API 来停止已经运行的线程。似乎 Executor#stop() 什么都不做。

我的 RestController:

@Autowired
private Executor executor;

@RequestMapping(path = "/start", method = GET)
public ResponseEntity<HttpStatus> startLongTask() {
    executor.start();
    return ResponseEntity.ok(HttpStatus.OK);
}

@RequestMapping(path = "/stop", method = GET)
public ResponseEntity<HttpStatus> stopLongTask() {
    executor.stop();
    return ResponseEntity.ok(HttpStatus.OK);
}

我的执行者:

@Component
public class Executor {

    @Value("${threads.number}")
    private int threadsNumber;

    private ExecutorService executorService;

    @Autowired
    private OtherService otherService;

    @PostConstruct
    private void init() {
        executorService = Executors.newFixedThreadPool(threadsNumber);
        executorService = Executors.newScheduledThreadPool(threadsNumber);
    }

    /**
     * Start.
     */
    public void start() {
        executorService.submit(() -> otherService.methodImExecuting());
    }

    /**
     * Stop.
     */
    @PreDestroy
    publicvoid stop() {
        executorService.shutdownNow();
        try {
            if (!executorService.awaitTermination(800, TimeUnit.MILLISECONDS)) {
                executorService.shutdownNow();
            }
        } catch (InterruptedException e) {
            executorService.shutdownNow();
        }
    }
}

这是methodImExecuting:

@Component
public class OtherService {

    public void methodImExecuting() {
        List<SomeObject> dataList = repository.getDataThatNeedsToBeFilled();
        for (SomeObject someObject : dataList) {
            gatewayService.sendDataToOtherResourceViaHttp(someObject);
        }
    }
}

Answer 1

简短回答:您无法停止不合作的正在运行的线程。线程有一个已弃用的 destroy() 方法，但这会导致您的 VM 处于“不良”状态。

干净地结束线程的唯一可能性是中断它。但是检查中断是线程本身的任务。

所以你的methodImExcecuting应该看起来像:

void methodImExecuting() throws InterruptedException {
    // it depends on your implementation, I assume here that you iterate 
    // over a collection for example
    int loopCount = 0;
    for (Foo foo : foos) {
        ++loopCount;
        if (loopCount % 100 == 0) {
            if (Thread.interrupted())
                throw new InterruptedException();
        }
        ...
    }

这取决于您的实现，如果您的线程被中断，您必须多久查看一次。但事实是，executorService.shutdownNow(); 的调用只会设置 executorService 当前运行的所有线程的 interrupted 标志。要真正中断线程，线程必须自己检查是否设置了 interrupted 标志，然后抛出 InterruptedException