Question

我想确保目录树中的正确权限（目录为0755，文件为644）。这是我的班级：

package NRF_Utils;

import java.io.IOException;
import java.nio.file.FileVisitResult;
import static java.nio.file.FileVisitResult.*;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Set;
import java.util.logging.Logger;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;

public class DirectoryTreeOperations {
    private static final Logger log = Logger.getLogger("spv." + DirectoryTreeOperations.class.getName());

    public static boolean setPermissions(String root, String directoryPermissions, String filePermissions) {
        boolean result = true;
        //declaring the path to delete
        final Path path = Paths.get(root);
        final Set<PosixFilePermission> dirPermissions = PosixFilePermissions.fromString(directoryPermissions);
        final Set<PosixFilePermission> filPermissions = PosixFilePermissions.fromString(filePermissions);

        try {
            Files.walkFileTree(path, new FileVisitor<Path>() {

                @Override
                public FileVisitResult preVisitDirectory(Path dir,
                        BasicFileAttributes attrs) throws IOException {
                    System.out.println("setting dir permission on " + dir);
                    Files.setPosixFilePermissions(dir, dirPermissions);                 
                    return CONTINUE;
                }

                @Override
                public FileVisitResult visitFile(Path file,
                        BasicFileAttributes attrs) throws IOException {
                    System.out.println("setting file permission on " + file);
                    Files.setPosixFilePermissions(file, filPermissions);
                    return CONTINUE;
                }

                @Override
                public FileVisitResult visitFileFailed(Path file, IOException exc)
                        throws IOException {
                    log.severe("visitFileFailed failed on " + file + " : " + exc);
                    return CONTINUE;
                }

                @Override
                public FileVisitResult postVisitDirectory(Path dir,
                        IOException exc) throws IOException {
                    return CONTINUE;
                }

            });
        } catch (IOException e) {
            log.severe("setPermissions failed " + e);
            result = false;
        }
        return result;
    }

    // TODO remove and provide a proper unit test
    public static void main(String [] arg) {
        System.out.println ("setPermissions returned: " + setPermissions("/tmp/x", "rwxr-xr-x", "rw-r--r--"));
    }
}

为了进行测试，我做了：

mkdir -p /tmp/x/y/z;touch /tmp/x/y/z/f;chmod 000 /tmp/x/y/z

输出结果为：

setting dir permission on /tmp/x
setting dir permission on /tmp/x/y
setPermissions returned: true
nov. 26, 2017 2:45:00 PM NRF_Utils.DirectoryTreeOperations$1 visitFileFailed
GRAVE: visitFileFailed failed on /tmp/x/y/z : java.nio.file.AccessDeniedException: /tmp/x/y/z

似乎java不想浏览目录树，因为权限错误，但我的目的是探索目录树来修复权限。 API是疯了吗？

Answer 1

它看起来似乎很奇怪，所以也许不是一个疯狂的API，但实现当然不能满足使用preVisitDirectory（）来使目录可访问的特定情况。

Files.walkFileTree() doc说：

如果文件是目录，并且无法打开目录，然后使用I / O异常调用visitFileFailed方法，之后，默认情况下，文件树步行继续在下一个步骤兄弟姐妹的目录。

并查看实现，它确实尝试在调用visitor.preVisitDirectory()之前打开目录，这解释了您遇到的问题。

作为一个解决方案，您可以获取FileTreeWalker.java源代码，并在您自己的本地版本的FileTreeWalker中进行微调 - 直接查找对visitor.preVisitDirectory()的调用并移动打开的目录代码在那之后发生。然后将您的代码更改为：

  new FileTreeWalker(EnumSet.noneOf(FileVisitOption.class), new FileVisitor<Path>() {
     ...
  }, Integer.MAX_VALUE).walk(path);

当你跑步时，你会得到：

setting dir permission on /tmp/x
setting dir permission on /tmp/x/y
setting dir permission on /tmp/x/y/z
setting file permission on /tmp/x/y/z/f
setPermissions returned: true

显示了FileVisitor的实施情况。

希望有所帮助。

Answer 2

当您从命令行执行chmod 755 /tmp/x/y/z时，它不会检查z本身的权限。只要您有足够的y访问权限，就可以在chmod上执行z。

OTOH，如果您查看Files.walkFileTree的{{3}}，它实际上会尝试使用自己的visit方法访问每个目标文件，收集文件属性等，之前它会调用您的访问者方法。因此拒绝访问错误。

从表面上看，您可能需要滚动自己的文件树助行器，在那里您可以继续更改权限，而无需先尝试访问目标路径。

Answer 3

DEFINE('DB_USER', 'root'); // default user name DEFINE('DB_PASSWORD', ''); // empty password just open single quote and close的唯一问题是它不会在没有搜索权限的目录上调用walkFileTree。您可以通过在walkFileTree查找的位置之前修复权限来解决此问题。即，通过手动扫描递送到preVisitDirectory()的任何目录的直接子项并在那里应用权限（而不是preVisitDirectoy()）：

visitFile

然后你可以评论@Override public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException { for(File f : new File(dir.toUri()).listFiles()) { //iterate over the contents of the directory System.out.println("setting dir permission on " + f); Files.setPosixFilePermissions(dir.resolve(f.getName()), dirPermissions); } //System.out.println("setting dir permission on " + dir); //Files.setPosixFilePermissions(dir, dirPermissions); return CONTINUE; }的身体：

visitFile()

由于我们现在将权限应用于walk所在的下一层，我们需要在try块内部进行额外的调用：

            @Override
            public FileVisitResult visitFile(Path file,
                    BasicFileAttributes attrs) throws IOException {
            //    System.out.println("setting file permission on " + file);
            //    Files.setPosixFilePermissions(file, filPermissions);
                return CONTINUE;
            }

以下是整个事情（好吧，为方便起见，我取消了包裹声明）：

        System.out.println("setting dir permission on " + path); //in case the initial path needs fixing
        Files.setPosixFilePermissions(path, dirPermissions);

在示例案例上运行时：

import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import static java.nio.file.FileVisitResult.*;
import java.nio.file.FileVisitor;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Set;
import java.util.logging.Logger;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;

public class DirectoryTreeOperations {
    private static final Logger log = Logger.getLogger("spv." + DirectoryTreeOperations.class.getName());

    public static boolean setPermissions(String root, String directoryPermissions, String filePermissions) {
        boolean result = true;
        //declaring the path to delete
        final Path path = Paths.get(root);
        final Set<PosixFilePermission> dirPermissions = PosixFilePermissions.fromString(directoryPermissions);
        final Set<PosixFilePermission> filPermissions = PosixFilePermissions.fromString(filePermissions);

        try {
            System.out.println("setting dir permission on " + path); //in case the initial path needs fixing
            Files.setPosixFilePermissions(path, dirPermissions);

            Files.walkFileTree(path, new FileVisitor<Path>() {
                @Override
                public FileVisitResult preVisitDirectory(Path dir,
                        BasicFileAttributes attrs) throws IOException {
                    for(File f : new File(dir.toUri()).listFiles()) { //iterate over the contents of the directory
                        System.out.println("setting dir permission on " + f);
                        Files.setPosixFilePermissions(dir.resolve(f.getName()), dirPermissions);
                    }

                    //System.out.println("setting dir permission on " + dir);
                    //Files.setPosixFilePermissions(dir, dirPermissions);
                    return CONTINUE;
                }

                @Override
                public FileVisitResult visitFile(Path file,
                        BasicFileAttributes attrs) throws IOException {
                //    System.out.println("setting file permission on " + file);
                //    Files.setPosixFilePermissions(file, filPermissions);
                    return CONTINUE;
                }

                @Override
                public FileVisitResult visitFileFailed(Path file, IOException exc)
                        throws IOException {
                    log.severe("visitFileFailed failed on " + file + " : " + exc);
                    return CONTINUE;
                }

                @Override
                public FileVisitResult postVisitDirectory(Path dir,
                        IOException exc) throws IOException {
                    return CONTINUE;
                }

            });
        } catch (IOException e) {
            log.severe("setPermissions failed " + e);
            result = false;
        }
        return result;
    }

    // TODO remove and provide a proper unit test
    public static void main(String [] arg) {
        System.out.println ("setPermissions returned: " + setPermissions("/tmp/x", "rwxr-xr-x", "rw-r--r--"));
    }
}

java walkFileTree模仿chmod -R 755不起作用

3 个答案: