jdk.nio.file.FileVisitor — clojure-interop/java.nio 1.0.5

A visitor of files. An implementation of this interface is provided to the Files.walkFileTree methods to visit each file in a file tree.

Usage Examples: Suppose we want to delete a file tree. In that case, each directory should be deleted after the entries in the directory are deleted.

Path start = ...
Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
    @Override
    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
        throws IOException
    {
        Files.delete(file);
        return FileVisitResult.CONTINUE;
    }
    @Override
    public FileVisitResult postVisitDirectory(Path dir, IOException e)
        throws IOException
    {
        if (e == null) {
            Files.delete(dir);
            return FileVisitResult.CONTINUE;
        } else {
            // directory iteration failed
            throw e;
        }
    }
});

Furthermore, suppose we want to copy a file tree to a target location. In that case, symbolic links should be followed and the target directory should be created before the entries in the directory are copied.

final Path source = ...
final Path target = ...

Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE,
    new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
            throws IOException
        {
            Path targetdir = target.resolve(source.relativize(dir));
            try {
                Files.copy(dir, targetdir);
            } catch (FileAlreadyExistsException e) {
                 if (!Files.isDirectory(targetdir))
                     throw e;
            }
            return CONTINUE;
        }
        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
            throws IOException
        {
            Files.copy(file, target.resolve(source.relativize(file)));
            return CONTINUE;
        }
    });

post-visit-directory clj

(post-visit-directory this dir exc)

Invoked for a directory after entries in the directory, and all of their descendants, have been visited. This method is also invoked when iteration of the directory completes prematurely (by a visitFile method returning SKIP_SIBLINGS, or an I/O error when iterating over the directory).

dir - a reference to the directory - T exc - null if the iteration of the directory completes without an error; otherwise the I/O exception that caused the iteration of the directory to complete prematurely - java.io.IOException

returns: the visit result - java.nio.file.FileVisitResult

throws: java.io.IOException - if an I/O error occurs

pre-visit-directory clj

(pre-visit-directory this dir attrs)

Invoked for a directory before entries in the directory are visited.

If this method returns CONTINUE, then entries in the directory are visited. If this method returns SKIP_SUBTREE or SKIP_SIBLINGS then entries in the directory (and any descendants) will not be visited.

dir - a reference to the directory - T attrs - the directory's basic attributes - java.nio.file.attribute.BasicFileAttributes

returns: the visit result - java.nio.file.FileVisitResult

throws: java.io.IOException - if an I/O error occurs

visit-file clj

(visit-file this file attrs)

Invoked for a file in a directory.

file - a reference to the file - T attrs - the file's basic attributes - java.nio.file.attribute.BasicFileAttributes

returns: the visit result - java.nio.file.FileVisitResult

throws: java.io.IOException - if an I/O error occurs

visit-file-failed clj

(visit-file-failed this file exc)

Invoked for a file that could not be visited. This method is invoked if the file's attributes could not be read, the file is a directory that could not be opened, and other reasons.

file - a reference to the file - T exc - the I/O exception that prevented the file from being visited - java.io.IOException

returns: the visit result - java.nio.file.FileVisitResult

throws: java.io.IOException - if an I/O error occurs