java - 如何关闭并行流中使用的线程本地自动关闭？

Question

我有一个 ThreadLocal 变量。我想这样使用它：

ThreadLocal<AutoCloseable> threadLocal = new ThreadLocal<AutoCloseable>(); // pseudocode
ForkJoinPool fj = new ForkJoinPool(nThreads);
fj.submit(
    () -> myStream.parallel().forEach(e -> {
        /*I want to use the thread local autocloseable here, 
          but how do I close it when this parallel processing is done?*/
    })
);

标签： javajava-8java-stream

Answer 1

ThreadLocal 在使用它们的线程死亡后关闭。如果你想控制这个，你需要使用地图。

// do our own thread local resources which close when we want.
Map<Thread, Resource> threadLocalMap = new ConcurrentHashMap<>();

fj.submit(
() -> myStream.parallel().forEach(e -> {
     Resource r = threadLocalMap.computeIfAbsent(Thread.currentThread(), t -> new Resource();
    // use the thread local autocloseable here, 
})

// later once all the tasks have finished.
// close all the thread local resources when the parallel processing is done
threadLocalMap.values().forEach(Utils::closeQuietly);

通常有一种方法可以在不引发异常的情况下关闭资源。Chronicle 有一个，但许多其他库也有。

public static void closeQuietly(Closeable c) {
    if (c != null) {
       try {
           c.close();
       } catch (IOException ioe) {
           // ignore or trace log it
       }
    }
}

很可能您的项目中已经有一种方法可以做到这一点 https://www.google.co.uk/search?q=public+static+void+closequietly+Closeable