为什么Java 7 Files.walkFileTree在遇到远程驱动器上的tar文件时抛出异常

Question

我Files.WalkFileTree()用来导航文件夹和计算音频文件,但遇到tar文件时出现问题,它似乎将它视为一个实际的文件夹我期望它只是跳过它.

我看不到任何让我控制这种行为的选项

码:

package com.jthink.songkong.fileloader;


import com.jthink.songkong.cmdline.SongKong;
import com.jthink.songkong.ui.MainWindow;

import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.concurrent.Callable;
import java.util.logging.Level;

/**
 * Count the number of files that can be loaded, for information purposes only
 */
public class CountFilesinFolder implements Callable<Boolean> {
    public static class CountFiles
            extends SimpleFileVisitor<Path> {
        private int fileCount = 0;
        private final PathMatcher matcher;

        CountFiles(String pattern) {
            matcher =
                    FileSystems.getDefault()
                            .getPathMatcher("regex:" + pattern);
        }

        /**
         * Find Music file
         *
         * @param file
         * @param attr
         * @return
         */
        @Override
        public FileVisitResult visitFile(Path file,
                                         BasicFileAttributes attr) {
            Path name = file.getFileName();
            if (name != null && matcher.matches(name)) {
                fileCount++;
            }
            return FileVisitResult.CONTINUE;
        }

        public int getFileCount() {
            return fileCount;
        }
    }


    private Path scanDir;
    public CountFilesinFolder(Path scanDir) {
        this.scanDir = scanDir;
    }

    public Boolean call() {
        CountFiles countFiles = null;
        try {
            countFiles = new CountFiles("^(?!._).*[.](?:mp3|mp4|m4p|m4b|m4a|ogg|flac|wma)$");
            Files.walkFileTree(scanDir, countFiles);
        }
        catch (Exception e) {
            MainWindow.logger.log(Level.SEVERE, "Unable to find file for deriving base folder", e);
        }
        MainWindow.logger.severe("Music File Count:"+countFiles.getFileCount());
        SongKong.setMaxProgress(countFiles.getFileCount());
        return true;
    }
}

给出了这个堆栈跟踪

java.nio.file.NoSuchFileException: Z:\Scratch\fred.tar
    at sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:79)
    at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:97)
    at sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:102)
    at sun.nio.fs.WindowsDirectoryStream.<init>(WindowsDirectoryStream.java:86)
    at sun.nio.fs.WindowsFileSystemProvider.newDirectoryStream(WindowsFileSystemProvider.java:526)
    at java.nio.file.Files.newDirectoryStream(Files.java:411)
    at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:179)
    at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:199)
    at java.nio.file.FileTreeWalker.walk(FileTreeWalker.java:69)
    at java.nio.file.Files.walkFileTree(Files.java:2591)
    at java.nio.file.Files.walkFileTree(Files.java:2624)
    at com.jthink.songkong.fileloader.CountFilesinFolder.call(CountFilesinFolder.java:68)
    at com.jthink.songkong.fileloader.CountFilesinFolder.call(CountFilesinFolder.java:15)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
    at java.util.concurrent.FutureTask.run(FutureTask.java:166)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

但这是一个远程驱动器(nas驱动器),我在本地驱动器上没有这样的错误

编辑 实现以下基于我认为有效的答案

    @Override
            public FileVisitResult preVisitDirectory(Path dir, 
BasicFileAttributes attrs)
                    throws IOException {
                if(dir.endsWith(".tar"))
                {
                    return FileVisitResult.SKIP_SUBTREE;
                }
                return super.preVisitDirectory(dir, attrs);
            }

但我的测试是不对的,它实际上并不起作用,因为FileTreeWalker中的代码失败是在previsit方法之前调用的

try {
            DirectoryStream<Path> stream = null;
            FileVisitResult result;

            // open the directory
            try {
                stream = Files.newDirectoryStream(file);
            } catch (IOException x) {
                return visitor.visitFileFailed(file, x);
            } catch (SecurityException x) {
                // ignore, as per spec
                return FileVisitResult.CONTINUE;
            }

            // the exception notified to the postVisitDirectory method
            IOException ioe = null;

            // invoke preVisitDirectory and then visit each entry
            try {
                result = visitor.preVisitDirectory(file, attrs);
                if (result != FileVisitResult.CONTINUE) {
                    return result;
                }

Answer 1

当前问题的解决方法：

但实施一个visitFileFailed，你应该没问题。

public class MyFileVisitor extends SimpleFileVisitor<Path> {
    @Override
    public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
        if (file.toString().endsWith(".tar")) {
            return FileVisitResult.CONTINUE;
        }
        return super.visitFileFailed(file, exc);
    }
}

更新：如果我们仔细观察，我们可以看到walkFileTree使用Files.readAttributes 来转向当前提供程序：WindowsFileSystemProvider.readAttributes来确定路径是否是目录。

正如有人在评论中提到的，我也不认为错误在于 Java 实现，而是返回错误属性的操作系统本机调用

如果您想为此解决方法，一个选择是实现您自己的文件系统，透明地包装 WindowsFileSystem 实现，但 readAttributes 返回 .tar-paths 作为文件而不是目录。