Java library to return a List<File> for glob or Ant-like pattern "*foo/**/*.txt"?

Question

I'm looking for a lib which would provide a method which would give me a list of files matching given Ant-like pattern.

For *foo/**/*.txt I'd get

foo/x.txt
foo/bar/baz/.txt
myfoo/baz/boo/bar.txt

etc. I know it's achievable with DirWalker and

PathMatcher mat = FileSystems.getDefault().getPathMatcher("glob:" + filesPattern);

, but I'd rather some maintained lib. I expected Commons IO to have it but no.

Update: I'm happy with reusing Ant's code, but would prefer something smaller than whole Ant.

Answer 1

As of Java 7 there is a recursive directory scan. Java 8 can improve it a bit syntactically.

    Path start = FileSystems.getDefault().getPath(",,,");
    walk(start, "**.java");

One needs a glob matching class, best on directory level, so as to skip directories.

class Glob {
    public boolean matchesFile(Path path) {
        return ...;
    }
    
    public boolean matchesParentDir(Path path) {
        return ...;
    }
}

Then the walking would be:

public static void walk(Path start, String searchGlob) throws IOException {
    final Glob glob = new Glob(searchGlob);
    Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult visitFile(Path file,
                BasicFileAttributes attrs) throws IOException {
            if (glob.matchesFile(file)) {
                ...; // Process file
            }
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult preVisitDirectory(Path dir,
                BasicFileAttributes attrs) throws IOException {
            return glob.matchesParentDir(dir)
                ? FileVisitResult.CONTINUE : FileVisitResult.SKIP_SUBTREE;
        }
    });
}

Answer 2

Google Guava has a TreeTraverser for files that lets you do depth-first and breadth-first enumeration of files in a directory. You could then filter the results based on a regex of the filename, or anything else you need to do.

Here's an example (requires Guava):

import java.io.File;
import java.util.List;
import java.util.regex.Pattern;
import com.google.common.base.Function;
import com.google.common.base.Predicates;
import com.google.common.io.Files;
import com.google.common.collect.Iterables;
import com.google.common.collect.TreeTraverser;

public class FileTraversalExample {

  private static final String PATH = "/path/to/your/maven/repo";
  private static final Pattern SEARCH_PATTERN = Pattern.compile(".*\\.jar");

  public static void main(String[] args) {
    File directory = new File(PATH);
    TreeTraverser<File> traverser = Files.fileTreeTraverser();
    Iterable<String> allFiles = Iterables.transform(
        traverser.breadthFirstTraversal(directory),
        new FileNameProducingPredicate());
    Iterable<String> matches = Iterables.filter(
      allFiles,
      Predicates.contains(SEARCH_PATTERN));
    System.out.println(matches);
  }

  private static class FileNameProducingPredicate implements Function<File, String> {
    public String apply(File input) {
      return input.getAbsolutePath();
    }
  }

}

Guava will let you filter by any Predicate, using Iterables.filter, so you don't have to use a Pattern if you don't want to.

Answer 3

So I sacrified few MB of app's size for the sake of speed and used Ant's DirectoryScanner in the end.

Also, there's Spring's PathMatchingResourcePatternResolver.

//files = new PatternDirWalker( filesPattern ).list( baseDir );
files = new DirScanner( filesPattern ).list( baseDir );


public class DirScanner {

    private String pattern;

    public DirScanner( String pattern ) {
        this.pattern = pattern;
    }

    public List<File> list( File dirToScan ) throws IOException {

            DirectoryScanner ds = new DirectoryScanner();
            String[] includes = {  this.pattern };
            //String[] excludes = {"modules\\*\\**"};
            ds.setIncludes(includes);
            //ds.setExcludes(excludes);
            ds.setBasedir( dirToScan );
            //ds.setCaseSensitive(true);
            ds.scan();

            String[] matches = ds.getIncludedFiles();
            List<File> files = new ArrayList(matches.length);
            for (int i = 0; i < matches.length; i++) {
                files.add( new File(matches[i]) );
            }
            return files;
    }

}// class

And here's my impl I started to code, not finished, just if someone would like to finish it. The idea was it would keep a stack of patterns, traverse the dir tree and compare the contents to the actual stack depth and the rest of it in case of **.

But I resorted to PathMatcher and then to Ant's impl.

public class PatternDirWalker {
    //private static final Logger log = LoggerFactory.getLogger( PatternDirWalker.class );

    private String pattern;
    private List segments;
    private PathMatcher mat;

    public PatternDirWalker( String pattern ) {
        this.pattern = pattern;
        this.segments = parseSegments(pattern);
        this.mat = FileSystems.getDefault().getPathMatcher("glob:" + pattern);
    }

    public List<File> list( File dirToScan ) throws IOException{

        return new DirectoryWalker() {
            List<File> files = new LinkedList();

            @Override protected void handleFile( File file, int depth, Collection results ) throws IOException {
                if( PatternDirWalker.this.mat.matches( file.toPath()) )
                    results.add( file );
            }

            public List<File> findMatchingFiles( File dirToWalk ) throws IOException {
                this.walk( dirToWalk, this.files );
                return this.files;
            }
        }.findMatchingFiles( dirToScan );

    }// list()

    private List<Segment> parseSegments( String pattern ) {
        String[] parts = StringUtils.split("/", pattern);
        List<Segment> segs = new ArrayList(parts.length);
        for( String part : parts ) {
            Segment seg = new Segment(part);
            segs.add( seg );
        }
        return segs;
    }

    class Segment {
        public final String pat;  // TODO: Tokenize
        private Segment( String pat ) {
            this.pat = pat;
        }
    }

}// class