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 [英] Why is Java 7 Files.walkFileTree throwing exception on encountering a tar file on remote drive
问题描述
我使用 Files.WalkFileTree（）来导航文件夹和计算音频文件，但遇到tar文件时出现问题，似乎将其视为一个实际的文件夹，我期待它只是跳过它。
Im using Files.WalkFileTree() to navigate folder and counting audio files, but there is a problem when it encounters a tar file, it seems to be treating it as an actual folder I was expecting it to just skip over it.
我看不到任何让我控制这种行为的选项
I cannot see any options that let me control this behaviour
代码：
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出现这样的错误
but that is a a remote drive (nas drive), I get no such error on local drive
编辑
实现以下基于我认为有效的答案
EDIT Implemented the following based o the answer below I thought worked
@Override
public FileVisitResult preVisitDirectory(Path dir,
BasicFileAttributes attrs)
throws IOException {
if(dir.endsWith(".tar"))
{
return FileVisitResult.SKIP_SUBTREE;
}
return super.preVisitDirectory(dir, attrs);
}
但是我的测试结果不对，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
but my testing was amiss, it doesnt in fact work because the code in FileTreeWalker that fails is called before the previsit method
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;
}
推荐答案
手头问题的解决方法：
但实现了visitFileFailed，你应该没问题。
But implement a visitFileFailed and you should be ok.
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 转向当前的提供者： WindowsFileSystemProvider.readAttributes 以确定路径是否是目录。
Update: If we look closer we can see that walkFileTree uses the Files.readAttributes which turns to the current provider in play: WindowsFileSystemProvider.readAttributes to determine if a path is a directory.
正如评论中提到的那样我也不认为错误是在Java实现中，而是 OS-native-call 返回错误的属性
As someone mentioned in the comments I also dont think the fault is in the Java-implementation but the OS-native-call that returns the wrong attribute
如果你想为此做一个解决方法，一个选项就是实现你自己的文件系统透明地包装WindowsFileSystem实现，除了readAttributes返回.tar-paths作为文件而不是DIR。
If you wanted to do a workaround for this, one option would be to implement your own FileSystem that wraps the WindowsFileSystem implementation transparently, except readAttributes returns .tar-paths as file instead of dir.
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