source: src/main/java/weka/core/ClassloaderUtil.java @ 6

/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    ClassloaderUtil.java
 *    Copyright (C) 2008 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

/**
 * Utility class that can add jar files to the classpath dynamically.
 *
 * @author Mark Hall (mhall{[at]}pentaho{[dot]}org
 * @version  $Revision: 5953 $
 */
public class ClassloaderUtil
  implements RevisionHandler {

  // Parameters
  private static final Class[] parameters = new Class[]{URL.class};

  /**
   * Add file to CLASSPATH
   * @param s File name
   * @throws IOException if something goes wrong when adding a file
   */
  public static void addFile(String s) throws IOException {
    File f = new File(s);
    addFile(f);
  }

  /**
   * Add file to CLASSPATH
   * @param f  File object
   * @throws IOException if something goes wrong when adding a file
   */
  public static void addFile(File f) throws IOException {
    addURL(f.toURL());
  }

  /**
   * Add URL to CLASSPATH
   * @param u URL
   * @throws IOException if something goes wrong when adding a url
   */
  public static void addURL(URL u) throws IOException {
    ClassloaderUtil clu = new ClassloaderUtil();
    //        URLClassLoader sysLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
    URLClassLoader sysLoader = (URLClassLoader) clu.getClass().getClassLoader();
    URL urls[] = sysLoader.getURLs();
    for (int i = 0; i < urls.length; i++) {
      if (urls[i].toString().toLowerCase().equals(u.toString().toLowerCase())) {
        System.err.println("URL " + u + " is already in the CLASSPATH");
        return;
      }
    }
    Class<?> sysclass = URLClassLoader.class;
    try {
      Method method = sysclass.getDeclaredMethod("addURL", parameters);
      method.setAccessible(true);
      method.invoke(sysLoader, new Object[]{u});
    } catch (Throwable t) {
      t.printStackTrace();
      throw new IOException("Error, could not add URL to system classloader");
    }
  }
  
  /**
   * Returns the revision string.
   * 
   * @return            the revision
   */
  public String getRevision() {
    return RevisionUtils.extract("$Revision: 5953 $");
  }
}