ReflectionUtils.java

package edu.berkeley.nlp.util;

import java.io.File;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.*;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

/**
 * Created by IntelliJ IDEA.
 * User: aria42
 * Date: Dec 7, 2008
 */
public class ReflectionUtils {

  public static List<Class> getClassesForPackage(String pckgname) {
    List<Class> classes = new ArrayList<Class>();
    ArrayList<File> directories = new ArrayList<File>();
    char fileSep = System.getProperty("file.separator").charAt(0);
    try {
      ClassLoader cld = Thread.currentThread().getContextClassLoader();
      if (cld == null) {
        throw new ClassNotFoundException("Can't get class loader.");
      }
      Enumeration<URL> resources = cld.getResources(pckgname.replace('.', fileSep));
      while (resources.hasMoreElements()) {
        URL res = resources.nextElement();
        if (res.getProtocol().equalsIgnoreCase("jar")) {
          JarURLConnection conn = (JarURLConnection) res.openConnection();
          JarFile jar = conn.getJarFile();
          for (JarEntry e : Collections.list(jar.entries())) {
            if (e.getName().startsWith(pckgname.replace('.', fileSep))
                && e.getName().endsWith(".class") && !e.getName().contains("$")) {
              String className =
                  e.getName().replace(""+ fileSep, ".").substring(0, e.getName().length() - 6);              
              classes.add(Class.forName(className));
            }
          }
        } else {
          directories.add(new File(URLDecoder.decode(res.getPath(), "UTF-8")));
        }
      }
    } catch (Exception e) {
      e.printStackTrace();    
    }

    for (File directory : directories) {
      if (directory.exists()) {
        String[] files = directory.list();
        for (String file : files) {
          if (file.endsWith(".class")) {
            String className = file.substring(0, file.length() - 6);
            try {
              classes.add(Class.forName(pckgname + '.' + className));
            } catch (ClassNotFoundException e) {
              e.printStackTrace();
            }
          }
        }
      } 
    }
    return classes;
  }

  public static List<Class> getClassessOfInterface(String thePackage, Class theInterface) {
    List<Class> classList = new ArrayList<Class>();
    try {
      for (Class discovered : getClassesForPackage(thePackage)) {
        if (Arrays.asList(discovered.getInterfaces()).contains(theInterface)) {
          classList.add(discovered);
        }
      }
    } catch (Exception e) {
      e.printStackTrace();
    }

    return classList;
  }

}