Question

I have a set of files in my Maven resource folder:

+ src
  + main
    + resources
      + mydir
        + myfile1.txt
        + myfile2.txt

How can I iterate mydir? Not only in Eclipse, but when running JUnit tests from the command line, and from a dependent jar.

File mydir = new File("mydir");
for (File f : dir.listFiles()) {
   dosomething...       
}

Thanks for a hint!

Answer 1

In the end, this is what I came up with to handle accessing files within referenced jars:

public class ResourceHelper {

    public static File getFile(String resourceOrFile)
        throws FileNotFoundException {
    try {

        // jar:file:/home/.../blue.jar!/path/to/file.xml
        URI uri = getURL(resourceOrFile).toURI();
        String uriStr = uri.toString();
        if (uriStr.startsWith("jar")) {

        if (uriStr.endsWith("/")) {
            throw new UnsupportedOperationException(
                "cannot unjar directories, only files");
        }

        String jarPath = uriStr.substring(4, uriStr.indexOf("!"))
            .replace("file:", "");
        String filePath = uriStr.substring(uriStr.indexOf("!") + 2);

        JarFile jarFile = new JarFile(jarPath);
        assert (jarFile.size() > 0) : "no jarFile at " + jarPath;

        Enumeration<JarEntry> entries = jarFile.entries();

        while (entries.hasMoreElements()) {

            JarEntry jarEntry = entries.nextElement();
            if (jarEntry.toString().equals(filePath)) {
            InputStream input = jarFile.getInputStream(jarEntry);
            assert (input != null) : "empty is for " + jarEntry;
            return tmpFileFromStream(input, filePath);
            }
        }
        assert (false) : "file" + filePath + " not found in " + jarPath;
        return null;
        } else {
        return new File(uri);
        }

    } catch (URISyntaxException e) {
        throw new FileNotFoundException(resourceOrFile);
    } catch (IOException e) {
        throw new FileNotFoundException(resourceOrFile);
    }
    }

    private static File tmpFileFromStream(InputStream is, String filePath)
        throws IOException {

    String fileName = filePath.substring(filePath.lastIndexOf("/") + 1,
        filePath.lastIndexOf("."));
    assert (fileName != null) : "filename cannot be null for " + filePath;
    String extension = filePath.substring(filePath.lastIndexOf("."));
    assert (extension != null) : "extension cannot be null for " + filePath;

    File tmpFile = File.createTempFile(fileName, extension);
    // tempFile.deleteOnExit();
    assert (tmpFile.exists()) : "could not create tempfile";

    OutputStream out = new FileOutputStream(tmpFile);
    int read = 0;
    byte[] bytes = new byte[1024];
    while ((read = is.read(bytes)) != -1) {
        out.write(bytes, 0, read);
    }
    is.close();
    out.flush();
    out.close();
    assert (tmpFile.length() > 0) : "file empty "
        + tmpFile.getAbsolutePath();
    return tmpFile;
    }

    public static File getTempFile(String resourceOrFile) throws IOException {

    InputStream input = getInputStream(resourceOrFile);

    File tempFile = IOUtils.createTempDir();
    tempFile.deleteOnExit();
    FileOutputStream output = new FileOutputStream(tempFile);

    byte[] buffer = new byte[4096];
    int bytesRead = input.read(buffer);
    while (bytesRead != -1) {
        output.write(buffer, 0, bytesRead);
        bytesRead = input.read(buffer);
    }
    output.close();
    input.close();

    return tempFile;
    }

    public static InputStream getInputStream(String resourceOrFile)
        throws FileNotFoundException {

    try {
        return getURL(resourceOrFile).openStream();
    } catch (Exception e) {
        throw new FileNotFoundException(resourceOrFile);
    }
    }

    public static URL getURL(String resourceOrFile)
        throws FileNotFoundException {

    File file = new File(resourceOrFile);
    // System.out.println("checking file ");
    // is file
    if (file.exists()) {
        // System.out.println("file exists");
        try {
        return file.toURI().toURL();
        } catch (MalformedURLException e) {
        throw new FileNotFoundException(resourceOrFile);
        }
    }
    // is resource
    if (!file.exists()) {
        // System.out.println("file resource");
        URL url = Thread.class.getResource(resourceOrFile);
        if (url != null) {
        return url;
        }
        url = Thread.class.getResource("/" + resourceOrFile);
        if (url != null) {
        return url;
        }
    }
    throw new FileNotFoundException(resourceOrFile);
    }
}