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Victor Tatai

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Get All Classes Within A Package

11.30.2007

| 96726 views |

        The code below gets all classes within a given package. Notice that it should only work for classes found locally, getting really ALL classes is impossible.

    /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
     *
     * @param packageName The base package
     * @return The classes
     * @throws ClassNotFoundException
     * @throws IOException
     */
    private static Class[] getClasses(String packageName)
            throws ClassNotFoundException, IOException {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        assert classLoader != null;
        String path = packageName.replace('.', '/');
        Enumeration<URL> resources = classLoader.getResources(path);
        List<File> dirs = new ArrayList<File>();
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        ArrayList<Class> classes = new ArrayList<Class>();
        for (File directory : dirs) {
            classes.addAll(findClasses(directory, packageName));
        }
        return classes.toArray(new Class[classes.size()]);
    }

    /**
     * Recursive method used to find all classes in a given directory and subdirs.
     *
     * @param directory   The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return The classes
     * @throws ClassNotFoundException
     */
    private static List<Class> findClasses(File directory, String packageName) throws ClassNotFoundException {
        List<Class> classes = new ArrayList<Class>();
        if (!directory.exists()) {
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file, packageName + "." + file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
            }
        }
        return classes;
    }

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Comments

Carla Brian replied on Mon, 2012/07/16 - 6:03pm

This is really cool. This might be helpful in the future. I could use this and this would be really effective. - Mercy Ministries

Snippets Manager replied on Tue, 2010/02/16 - 4:31pm

Another way to handle spaces (or other non-alphanumeric characters) in file names is to use the URL.toURI() method: dirs.add(new File(resource.toURI())); On the downside, you now have to add URISyntaxException to the throws clause of getClasses()

Snippets Manager replied on Fri, 2012/05/04 - 5:05am

This does not work if the package is not located under the current project. How do i have to proceed to load classes from a zip file located anywhere? Would you help me please?

Vítor Souza replied on Fri, 2012/02/17 - 12:35pm

This will not work in the Activator of an OSGi bundle (at least the code from the latest comment, which I tried). Here's how I solved it:

public void start(BundleContext bundleContext) throws Exception {
	Bundle bundle = bundleContext.getBundle();
	BundleWiring wiring = bundle.adapt(BundleWiring.class);
	Collection resources = wiring.listResources(PACKAGE_QUALIFIED_NAME.replace('.', '/'), "*.class", 0); //$NON-NLS-1$

	for (String resource : resources) {
		// Replace slashes back to dots and remove the trailling ".class" from the file name to form the qualified name of the class.
		resource = resource.replace('/', '.').substring(0, resource.length() - 6);
		Class clazz = bundle.loadClass(resource);

		// Do something with the class...
	}
}

BundleWiring is org.osgi.framework.wiring.BundleWiring, other OSGi classes are from org.osgi.framework.*. Hope it helps someone...

Snippets Manager replied on Wed, 2012/02/01 - 3:05pm

I agree, this saved some time for me. Have to make one more tweak though. In the case of jar/zip files, you are properly searching them but not properly filtering by the original package name.


if (className.startsWith(packageName) && (regex == null || regex.matcher(className).matches()))
						classes.add(className);

I also added a simple regex filter, useful as well.


	/**
	 * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
	 * Adapted from http://snippets.dzone.com/posts/show/4831 and extended to support use of JAR files
	 *
	 * @param packageName The base package
	 * @param regexFilter an optional class name pattern.
	 * @return The classes
	 */
	public static Class[] getClassesInPackage(String packageName, String regexFilter) {
		Pattern regex = null;
		if (regexFilter != null)
			regex = Pattern.compile(regexFilter);

		try {
			ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
			assert classLoader != null;
			String path = packageName.replace('.', '/');
			Enumeration resources = classLoader.getResources(path);
			List dirs = new ArrayList();
			while (resources.hasMoreElements()) {
				URL resource = resources.nextElement();
				dirs.add(resource.getFile());
			}
			TreeSet classes = new TreeSet();
			for (String directory : dirs) {
				classes.addAll(findClasses(directory, packageName, regex));
			}
			ArrayList classList = new ArrayList();
			for (String clazz : classes) {
				classList.add(Class.forName(clazz));
			}
			return classList.toArray(new Class[classes.size()]);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}

	/**
	 * Recursive method used to find all classes in a given path (directory or zip file url).  Directories
	 * are searched recursively.  (zip files are
	 * Adapted from http://snippets.dzone.com/posts/show/4831 and extended to support use of JAR files
	 *
	 * @param path   The base directory or url from which to search.
	 * @param packageName The package name for classes found inside the base directory
	 * @param regex       an optional class name pattern.  e.g. .*Test
	 * @return The classes
	 */
	private static TreeSet findClasses(String path, String packageName, Pattern regex) throws Exception {
		TreeSet classes = new TreeSet();
		if (path.startsWith("file:") && path.contains("!")) {
			String[] split = path.split("!");
			URL jar = new URL(split[0]);
			ZipInputStream zip = new ZipInputStream(jar.openStream());
			ZipEntry entry;
			while ((entry = zip.getNextEntry()) != null) {
				if (entry.getName().endsWith(".class")) {
					String className = entry.getName().replaceAll("[$].*", "").replaceAll("[.]class", "").replace('/', '.');
					if (className.startsWith(packageName) && (regex == null || regex.matcher(className).matches()))
						classes.add(className);
				}
			}
		}
		File dir = new File(path);
		if (!dir.exists()) {
			return classes;
		}
		File[] files = dir.listFiles();
		for (File file : files) {
			if (file.isDirectory()) {
				assert !file.getName().contains(".");
				classes.addAll(findClasses(file.getAbsolutePath(), packageName + "." + file.getName(), regex));
			} else if (file.getName().endsWith(".class")) {
				String className = packageName + '.' + file.getName().substring(0, file.getName().length() - 6);
				if (regex == null || regex.matcher(className).matches())
					classes.add(className);
			}
		}
		return classes;
	}

Snippets Manager replied on Mon, 2012/01/23 - 4:07pm

The following code was adapted from above, but will work if the package is inside a jar, making it useful for distribution. It will load the class names from the executing Jar as well as all supporting Jars in the classpath. It uses a treeset with the classnames to avoid duplicate classnames and also to naturally order them.


  /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
     * Adapted from http://snippets.dzone.com/posts/show/4831 and extended to support use of JAR files
     * @param packageName The base package
     * @return The classes
     * @throws ClassNotFoundException
     * @throws IOException
     */
    public static Class[] getClasses(String packageName) {
      try {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        assert classLoader != null;
        String path = packageName.replace('.', '/');
        Enumeration resources = classLoader.getResources(path);
        List dirs = new ArrayList();
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            dirs.add(resource.getFile());
        }
        TreeSet classes = new TreeSet();
        for (String directory : dirs) {
          classes.addAll(findClasses(directory, packageName));
        }
        ArrayList classList = new ArrayList();
        for (String clazz : classes) {
          classList.add(Class.forName(clazz));
        }
        return classList.toArray(new Class[classes.size()]);
      }
      catch (Exception e) {
        e.printStackTrace();
        return null;
      }
    }
    
    /**
     * Recursive method used to find all classes in a given directory and subdirs.
     * Adapted from http://snippets.dzone.com/posts/show/4831 and extended to support use of JAR files
     * @param directory   The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return The classes
     * @throws ClassNotFoundException
     */
    private static TreeSet findClasses(String directory, String packageName) throws Exception {
        TreeSet classes = new TreeSet();
        if (directory.startsWith("file:") && directory.contains("!")) {
          String [] split = directory.split("!");
          URL jar = new URL(split[0]);
          ZipInputStream zip = new ZipInputStream(jar.openStream());
          ZipEntry entry = null;
          while ((entry = zip.getNextEntry()) != null) {
            if (entry.getName().endsWith(".class")) {
              String className = entry.getName().replaceAll("[$].*", "").replaceAll("[.]class", "").replace('/', '.');
                classes.add(className);
            }
          }
        }
        File dir = new File(directory);
        if (!dir.exists()) {
            return classes;
        }
        File[] files = dir.listFiles();
        for (File file : files) {
            if (file.isDirectory()) {
                assert !file.getName().contains(".");
                classes.addAll(findClasses(file.getAbsolutePath(), packageName + "." + file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(packageName + '.' + file.getName().substring(0, file.getName().length() - 6));
            }
        }
        return classes;
    }

Snippets Manager replied on Thu, 2009/11/26 - 12:35pm

Nice snippet, helped me a lot. Below is the same snippet with the following changes: - problems with URL-encoded file paths are fixed (the same problem, as reported by davidparks21) - skipped inner, private and anonyme classes (which appear with $ in the class name) - added check for the ExceptionInInitializerError on calls to Class.forName(), in which case Class.forName() variant without initialization is used to get the class

 
    /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages.
     *
     * @param packageName The base package
     * @return The classes
     * @throws ClassNotFoundException
     * @throws IOException
     */
    @SuppressWarnings("unchecked")
	private static List getClasses(String packageName)
            throws ClassNotFoundException, IOException 
    {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        assert classLoader != null;
        String path = packageName.replace('.', '/');
        Enumeration resources = classLoader.getResources(path);
        List dirs = new ArrayList();
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            String fileName = resource.getFile();
            String fileNameDecoded = URLDecoder.decode(fileName, "UTF-8");
            dirs.add(new File(fileNameDecoded));
        }
        ArrayList classes = new ArrayList();
        for (File directory : dirs) {
            classes.addAll(findClasses(directory, packageName));
        }
        return classes;
    }

    /**
     * Recursive method used to find all classes in a given directory and subdirs.
     *
     * @param directory   The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return The classes
     * @throws ClassNotFoundException
     */
    @SuppressWarnings("unchecked")
	private static List findClasses(File directory, String packageName) throws ClassNotFoundException 
	{
        List classes = new ArrayList();
        if (!directory.exists()) {
            return classes;
        }
        File[] files = directory.listFiles();
        for (File file : files) {
        	String fileName = file.getName();
            if (file.isDirectory()) {
                assert !fileName.contains(".");
            	classes.addAll(findClasses(file, packageName + "." + fileName));
            } else if (fileName.endsWith(".class") && !fileName.contains("$")) {
            	Class _class;
				try {
					_class = Class.forName(packageName + '.' + fileName.substring(0, fileName.length() - 6));
				} catch (ExceptionInInitializerError e) {
					// happen, for example, in classes, which depend on 
					// Spring to inject some beans, and which fail, 
					// if dependency is not fulfilled
					_class = Class.forName(packageName + '.' + fileName.substring(0, fileName.length() - 6),
							false, Thread.currentThread().getContextClassLoader());
				}
				classes.add(_class);
            }
        }
        return classes;
    }

David Parks replied on Tue, 2009/03/24 - 1:45pm

Great snippet of code, thanks. However, one change is required: This code does not work for directories with a space in the name (the use of URL passes back a URL encoded file name which isn't found by File.exists()) Quick fix (to handle file names with spaces): Replace the line shown below with the 2nd one shown: dirs.add(new File(resource.getFile())); dirs.add(new File(resource.getFile().replace("%20", " ")));