ClassUtils.java

package detective.common;

import groovy.lang.GroovyClassLoader;

import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

import sun.net.www.protocol.file.FileURLConnection;

public class ClassUtils {

  /**
   * Private helper method
   * 
   * @param directory The directory to start with
   * @param pckgname The package name to search for. Will be needed for getting the Class object.
   * @param classes if a file isn't loaded but still is in the directory
   * @throws ClassNotFoundException
   */
  private static void checkDirectory(File directory, String pckgname, ArrayList<Class<?>> classes)
      throws ClassNotFoundException {
    File tmpDirectory;

    if (directory.exists() && directory.isDirectory()) {
      final String[] files = directory.list();

      for (final String file : files) {
        if (file.endsWith(".class")) {
          try {
            String classname = pckgname + '.' + file.substring(0, file.length() - 6);
            classes.add(Class.forName(classname));
          } catch (final NoClassDefFoundError e) {
            // do nothing. this class hasn't been found by the
            // loader, and we don't care.
          }
        }
      }
      
      //Loop two times as we want always process current folder first then sub folders
      for (final String file : files) {
        if (file.endsWith(".class")) {
          
        } else if ((tmpDirectory = new File(directory, file)).isDirectory()) {
          checkDirectory(tmpDirectory, pckgname + "." + file, classes);
        }
      }
    }
  }

  /**
   * Private helper method.
   * 
   * @param connection the connection to the jar
   * @param pckgname the package name to search for
   * @param classes the current ArrayList of all classes. This method will simply add new classes.
   * @throws ClassNotFoundException if a file isn't loaded but still is in the jar file
   * @throws IOException if it can't correctly read from the jar file.
   */
  private static void checkJarFile(JarURLConnection connection, String pckgname,
      ArrayList<Class<?>> classes) throws ClassNotFoundException, IOException {
    final JarFile jarFile = connection.getJarFile();
    final Enumeration<JarEntry> entries = jarFile.entries();
    String name;

    for (JarEntry jarEntry = null; entries.hasMoreElements()
        && ((jarEntry = entries.nextElement()) != null);) {
      name = jarEntry.getName();

      if (name.contains(".class")) {
        name = name.substring(0, name.length() - 6).replace('/', '.');

        if (name.contains(pckgname)) {
          classes.add(Class.forName(name));
        }
      }
    }
  }

  /**
   * Attempts to list all the classes in the specified package as determined by the context class
   * loader
   * 
   * @param pckgname the package name to search
   * @return a list of classes that exist within that package
   * @throws ClassNotFoundException if something went wrong
   */
  public static ArrayList<Class<?>> getClassesForPackage(String pckgname)
      throws ClassNotFoundException {
    final ArrayList<Class<?>> classes = new ArrayList<Class<?>>();

    try {
      final ClassLoader cld = Thread.currentThread().getContextClassLoader();

      if (cld == null)
        throw new ClassNotFoundException("Can't get class loader.");

      final Enumeration<URL> resources = cld.getResources(pckgname.replace('.', '/'));
      URLConnection connection;

      for (URL url = null; resources.hasMoreElements() && ((url = resources.nextElement()) != null);) {
        try {
          connection = url.openConnection();

          if (connection instanceof JarURLConnection) {
            checkJarFile((JarURLConnection) connection, pckgname, classes);
          } else if (connection instanceof FileURLConnection) {
            try {
              checkDirectory(new File(URLDecoder.decode(url.getPath(), "UTF-8")), pckgname, classes);
            } catch (final UnsupportedEncodingException ex) {
              throw new ClassNotFoundException(pckgname
                  + " does not appear to be a valid package (Unsupported encoding)", ex);
            }
          } else
            throw new ClassNotFoundException(pckgname + " (" + url.getPath()
                + ") does not appear to be a valid package");
        } catch (final IOException ioex) {
          throw new ClassNotFoundException(
              "IOException was thrown when trying to get all resources for " + pckgname, ioex);
        }
      }
    } catch (final NullPointerException ex) {
      throw new ClassNotFoundException(pckgname
          + " does not appear to be a valid package (Null pointer exception)", ex);
    } catch (final IOException ioex) {
      throw new ClassNotFoundException(
          "IOException was thrown when trying to get all resources for " + pckgname, ioex);
    }

    return classes;
  }

}