Source for gnu.java.net.loader.FileURLLoader

   1: /* FileURLLoader.java -- a URLLoader for file URLs
   2:    Copyright (C) 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.net.loader;
  40: 
  41: 
  42: import java.io.File;
  43: import java.io.IOException;
  44: import java.net.URL;
  45: import java.net.URLClassLoader;
  46: import java.net.URLStreamHandlerFactory;
  47: import java.util.StringTokenizer;
  48: 
  49: /**
  50:  * A <code>FileURLLoader</code> is a type of <code>URLLoader</code>
  51:  * only loading from file url.
  52:  */
  53: public final class FileURLLoader extends URLLoader
  54: {
  55:   File dir; //the file for this file url
  56: 
  57:   public FileURLLoader(URLClassLoader classloader,
  58:                        URLStreamHandlerCache cache,
  59:                        URLStreamHandlerFactory factory,
  60:                        URL url, URL absoluteUrl)
  61:   {
  62:     super(classloader, cache, factory, url, absoluteUrl);
  63:     dir = new File(absoluteUrl.getFile());
  64:   }
  65: 
  66:   /** get resource with the name "name" in the file url */
  67:   public Resource getResource(String name)
  68:   {
  69:     try
  70:       {
  71:         // Make sure that all components in name are valid by walking through
  72:         // them
  73:         File file = walkPathComponents(name);
  74: 
  75:         if (file == null)
  76:           return null;
  77: 
  78:         return new FileResource(this, file);
  79:       }
  80:     catch (IOException e)
  81:       {
  82:         // Fall through...
  83:       }
  84:     return null;
  85:   }
  86: 
  87:   /**
  88:    * Walk all path tokens and check them for validity. At no moment, we are
  89:    * allowed to reach a directory located "above" the root directory, stored
  90:    * in "dir" property. We are also not allowed to enter a non existing
  91:    * directory or a non directory component (plain file, symbolic link, ...).
  92:    * An empty or null path is valid. Pathnames components are separated by
  93:    * <code>File.separatorChar</code>
  94:    *
  95:    * @param resourceFileName the name to be checked for validity.
  96:    * @return the canonical file pointed by the resourceFileName or null if the
  97:    *         walking failed
  98:    * @throws IOException in case of issue when creating the canonical
  99:    *           resulting file
 100:    * @see File#separatorChar
 101:    */
 102:   private File walkPathComponents(String resourceFileName) throws IOException
 103:   {
 104:     StringTokenizer stringTokenizer = new StringTokenizer(resourceFileName, File.separator);
 105:     File currentFile = dir;
 106:     int tokenCount = stringTokenizer.countTokens();
 107: 
 108:     for (int i = 0; i < tokenCount - 1; i++)
 109:       {
 110:         String currentToken = stringTokenizer.nextToken();
 111: 
 112:         // If we are at the root directory and trying to go up, the walking is
 113:         // finished with an error
 114:         if ("..".equals(currentToken) && currentFile.equals(dir))
 115:           return null;
 116: 
 117:         currentFile = new File(currentFile, currentToken);
 118: 
 119:         // If the current file doesn't exist or is not a directory, the walking is
 120:         // finished with an error
 121:         if (! (currentFile.exists() && currentFile.isDirectory()))
 122:           return null;
 123: 
 124:       }
 125: 
 126:     // Treat the last token differently, if it exists, because it does not need
 127:     // to be a directory
 128:     if (tokenCount > 0)
 129:       {
 130:         String currentToken = stringTokenizer.nextToken();
 131: 
 132:         if ("..".equals(currentToken) && currentFile.equals(dir))
 133:           return null;
 134: 
 135:         currentFile = new File(currentFile, currentToken);
 136: 
 137:         // If the current file doesn't exist, the walking is
 138:         // finished with an error
 139:         if (! currentFile.exists())
 140:           return null;
 141:     }
 142: 
 143:     return currentFile.getCanonicalFile();
 144:   }
 145: }