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FileClassLoader.java

package edu.ksu.cis.bandera.util;

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Bandera, a Java(TM) analysis and transformation toolkit           *
 * Copyright (C) 2000  Roby Joehanes (robbyjo@cis.ksu.edu)           *
 * All rights reserved.                                              *
 *                                                                   *
 * This work was done as a project in the SAnToS Laboratory,         *
 * Department of Computing and Information Sciences, Kansas State    *
 * University, USA (http://www.cis.ksu.edu/santos).                  *
 * It is understood that any modification not identified as such is  *
 * not covered by the preceding statement.                           *
 *                                                                   *
 * This work is free software; you can redistribute it and/or        *
 * modify it under the terms of the GNU Library General Public       *
 * License as published by the Free Software Foundation; either      *
 * version 2 of the License, or (at your option) any later version.  *
 *                                                                   *
 * This work 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 *
 * Library General Public License for more details.                  *
 *                                                                   *
 * You should have received a copy of the GNU Library General Public *
 * License along with this toolkit; if not, write to the             *
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,      *
 * Boston, MA  02111-1307, USA.                                      *
 *                                                                   *
 * Java is a trademark of Sun Microsystems, Inc.                     *
 *                                                                   *
 * To submit a bug report, send a comment, or get the latest news on *
 * this project and other SAnToS projects, please visit the web-site *
 *                http://www.cis.ksu.edu/santos                      *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

// Adapted from magelang.com tutorial.

import java.io.*;
import java.net.*;
import java.util.*;

public class FileClassLoader extends ClassLoader {

    private String root;
    public static FileClassLoader v = new FileClassLoader();
private FileClassLoader() {
     // root == null means that we're looking it through the java.class.path system
     // property
     root = null;
}
public FileClassLoader (String rootDir) {
     if (rootDir == null) throw new IllegalArgumentException ("Null root directory");
     root = rootDir;
}
public static Class load(String name) throws ClassNotFoundException
{
     return v.loadClass(name);
}
protected Class loadClass (String name, boolean resolve) throws ClassNotFoundException {

     // Since all support classes of loaded class use same class loader
     // must check subclass cache of classes for things like Object

     // Class loaded yet?
     Class c = findLoadedClass (name);
     if (c == null) {
          try {
               c = findSystemClass (name);
          } catch (Exception e) {
               // Ignore these
          }
     }

     if (c == null) {
          // Convert class name argument to filename
          // Convert package names into subdirectories
          String filename = name.replace ('.', File.separatorChar) + ".class";

          try {
               // Load class data from file and save in byte array
               byte data[] = loadClassData(filename);

               // Convert byte array to Class
               c = defineClass (name, data, 0, data.length);

               // If failed, throw exception
               if (c == null) throw new ClassNotFoundException (name);
          } catch (IOException e) {
               throw new ClassNotFoundException ("Error reading file: " + filename);
          }
     }

     // Resolve class definition if approrpriate
     if (resolve) resolveClass (c);

     // Return class just created
     return c ;
}
private byte[] loadClassData (String filename) throws IOException {
     // Create a file object relative to directory provided
     File f = null;

     if (root == null)
     {
          // Fetch from the classpath
          String classPath = System.getProperty("java.class.path");
          StringTokenizer tok = new StringTokenizer(classPath, File.pathSeparator);
          boolean found = false;

          while (tok.hasMoreTokens())
          {
               f = new File(tok.nextToken(), filename);
               if (f.exists()) { found = true; break; }
          }
          if (!found) throw new IOException(filename+" cannot be found in class path: "+classPath);
     } else f = new File (root, filename);

     // Get size of class file
     int size = (int)f.length();

     // Reserve space to read
     byte buff[] = new byte[size];

     // Get stream to read from
     FileInputStream fis = new FileInputStream(f);
     DataInputStream dis = new DataInputStream (fis);

     // Read in data
     dis.readFully (buff);

     // close stream
     dis.close();

     // return data
     return buff;
}
    public void setRootDirectory(String r)
    {
        if (r != null) root = r;
    }
}

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