如何从主线程超时java线程？

编程问答 2022-05-24

问题描述

我不熟悉在 Java 中使用 ExecutorService、Future 和 Runnable 来设置线程超时。我正在开发一个程序，我的主线程将调用另一个线程来解析 XML 文件，并且（出于安全目的）在一定时间后超时。我已经搜索了几个小时并阅读了许多 StackOverFlow 线程，但我似乎根本无法让主线程中断辅助线程。当我运行这个程序时，xml 解析器将永远解析大得离谱的文件，我似乎无法让它被中断。任何帮助将不胜感激。我的两个线程的代码如下。

public class xmlParser{
        private static class Parse implements Runnable {

                private final String xmlFile;

                public Parse(String xmlFile) {
                        this.xmlFile = xmlFile;
                }

                @Override
                public void run() {
                        try {
                                while (!Thread.interrupted()) {
                                        XMLReader xmlReader = XMLReaderFactory.createXMLReader();
                                        xmlReader.setContentHandler(new MyContentHandler());
                                        xmlReader.parse(new InputSource(xmlFile));
                        }
                }

                        catch (Exception e) {
                                System.err.println("TIMEOUT ERROR: Took too long to parse xml file.");
                                e.printstacktrace();

                        }
                }

        }

    public static void main(String[] args) throws InterruptedException {
        ExecutorService executor = Executors.newSingleThreadExecutor();
        Future future = executor.submit(new Parse(args[0]));
        try {
                future.get(1,TimeUnit.SECONDS);
        }
        catch (Exception e) {
                future.cancel(true);
        }
        finally {
                executor.shutdownNow();
        }

   }
}

注意：我知道 future.get(long timeout,TimeUnit unit) 会抛出多种类型的异常，稍后会处理。目前，我只是想让我的主线程在运行 1 秒后中断 Parse 线程。

解决方法

我尝试用更简单的工作来重现：

static class FiveSecJob implements Callable<String> {
    @Override
    public  String call() {
        long t0 = System.currentTimeMillis();
        try {
            Thread.sleep(5000);
            return "success";
        } catch (Exception e) {
            System.out.println("interrupted after " + (System.currentTimeMillis() - t0) / 1000d + "s: " + e);
            return e.getMessage();
        }
    }
}
@Test
public void testTimeout() {
    ExecutorService executor = Executors.newSingleThreadExecutor();
    Future<String> future = executor.submit(new FiveSecJob());
    String s = "initial value";
    try {
        s = future.get(1,TimeUnit.SECONDS);
    } catch (Exception e) {
        System.out.println("cancelling future (" + e + ")");
        future.cancel(true);
    } finally {
        executor.shutdownNow();
    }
    System.out.println("s: " + s);
}

它似乎像意向一样取消了作业。输出为：

cancelling future (java.util.concurrent.TimeoutException)
s: initial value
interrupted after 1.0s: java.lang.InterruptedException: sleep interrupted
executorserviceexecutorservicefuturetaskjavajavamultithreadingmultithreadingrunnable