Get a List of Resources from Classpath Directory

Get a list of resources from classpath directory

Custom Scanner

Implement your own scanner. For example:

(limitations of this solution are mentioned in the comments)

private List<String> getResourceFiles(String path) throws IOException {
    List<String> filenames = new ArrayList<>();

    try (
            InputStream in = getResourceAsStream(path);
            BufferedReader br = new BufferedReader(new InputStreamReader(in))) {
        String resource;

        while ((resource = br.readLine()) != null) {
            filenames.add(resource);
        }
    }

    return filenames;
}

private InputStream getResourceAsStream(String resource) {
    final InputStream in
            = getContextClassLoader().getResourceAsStream(resource);

    return in == null ? getClass().getResourceAsStream(resource) : in;
}

private ClassLoader getContextClassLoader() {
    return Thread.currentThread().getContextClassLoader();
}

Spring Framework

Use PathMatchingResourcePatternResolver from Spring Framework.

Ronmamo Reflections

The other techniques might be slow at runtime for huge CLASSPATH values. A faster solution is to use ronmamo's Reflections API, which precompiles the search at compile time.

How to locate all resources in classpath with a specified name?

You can use Enumeration getResources(String name) on the class loader to achieve the same.

For example:

Enumeration<URL> enumer = Thread.currentThread().getContextClassLoader().getResources("/Path/To/xyz.properties");
while (enumer.hasMoreElements()) {
    System.out.print(enumer.nextElement());
}

File list from classpath directory in running jar

I found solution. Below code worked for me:

public static String[] getResourceListing(Class clazz, String path) throws URISyntaxException, IOException
{
    URL dirURL = clazz.getClassLoader().getResource(path);
    if (dirURL != null && dirURL.getProtocol().equals("file"))
    {
        /* A file path: easy enough */
        return new File(dirURL.toURI()).list();
    }

    if (dirURL == null)
    {
        /*
         * In case of a jar file, we can't actually find a directory. Have to assume the
         * same jar as clazz.
         */
        String me = clazz.getName().replace(".", "/") + ".class";
        dirURL = clazz.getClassLoader().getResource(me);
    }

    if (dirURL.getProtocol().equals("jar"))
    {
        /* A JAR path */
        String jarPath = dirURL.getPath().substring(5, dirURL.getPath().indexOf("!")); // strip out only the JAR file
        JarFile jar = new JarFile(URLDecoder.decode(jarPath, "UTF-8"));
        Enumeration<JarEntry> entries = jar.entries(); // gives ALL entries in jar
        Set<String> result = new HashSet<String>(); // avoid duplicates in case it is a subdirectory
        while (entries.hasMoreElements())
        {
            String name = entries.nextElement().getName();
            if (name.startsWith(path))
            { // filter according to the path
                String entry = name.substring(path.length());
                int checkSubdir = entry.indexOf("/");
                if (checkSubdir >= 0)
                {
                    // if it is a subdirectory, we just return the directory name
                    entry = entry.substring(0, checkSubdir);
                }
                result.add(entry);
            }
        }
        return result.toArray(new String[result.size()]);
    }

    throw new UnsupportedOperationException("Cannot list files for URL " + dirURL);
}