multipartrequest.java

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    String name = dispInfo[1];
    String filename = dispInfo[2];

    // Now onto the next line.  This will either be empty 
    // or contain a Content-Type and then an empty line.
    line = in.readLine();
    if (line == null) {
      // No parts left, we're done
      return true;
    }

    // Get the content type, or null if none specified
    String contentType = extractContentType(line);
    if (contentType != null) {
      // Eat the empty line
      line = in.readLine();
      if (line == null || line.length() > 0) {  // line should be empty
        throw new 
          IOException("Malformed line after content type: " + line);
      }
    }
    else {
      // Assume a default content type
      contentType = "application/octet-stream";
    }

    // Now, finally, we read the content (end after reading the boundary)
    if (filename == null) {
      // This is a parameter
      String value = readParameter(in, boundary);
      parameters.put(name, value);
    }
    else {
      // This is a file
      readAndSaveFile(in, boundary, filename);
      if (filename.equals("unknown")) {
        files.put(name, new UploadedFile(null, null, null));
      }
      else {
        files.put(name,
          new UploadedFile(dir.toString(), filename, contentType));
      }
    }
    return false;  // there's more to read
  }

  /**
   * A utility method that reads a single part of the multipart request 
   * that represents a parameter.  A subclass can override this method 
   * for a better optimized or differently behaved implementation.
   *
   * @param in the stream from which to read the parameter information
   * @param boundary the boundary signifying the end of this part
   * @return the parameter value
   * @exception IOException if there's a problem reading or parsing the 
   * request
   */
  protected String readParameter(MultipartInputStreamHandler in,
                                 String boundary) throws IOException {
    StringBuffer sbuf = new StringBuffer();
    String line;

    while ((line = in.readLine()) != null) {
      if (line.startsWith(boundary)) break;
      sbuf.append(line + "\r\n");  // add the \r\n in case there are many lines
    }

    if (sbuf.length() == 0) {
      return null;  // nothing read
    }

    sbuf.setLength(sbuf.length() - 2);  // cut off the last line's \r\n
    return sbuf.toString();  // no URL decoding needed
  }

  /**
   * A utility method that reads a single part of the multipart request 
   * that represents a file, and saves the file to the given directory.
   * A subclass can override this method for a better optimized or 
   * differently behaved implementation.
   *
   * @param in the stream from which to read the file
   * @param boundary the boundary signifying the end of this part
   * @param dir the directory in which to save the uploaded file
   * @param filename the name under which to save the uploaded file
   * @exception IOException if there's a problem reading or parsing the 
   * request
   */
  protected void readAndSaveFile(MultipartInputStreamHandler in,
                                 String boundary,
                                 String filename) throws IOException {
    File f = new File(dir + File.separator + filename);
    FileOutputStream fos = new FileOutputStream(f);
    BufferedOutputStream out = new BufferedOutputStream(fos, 8 * 1024); // 8K

    byte[] bbuf = new byte[100 * 1024];  // 100K
    int result;
    String line;

    // ServletInputStream.readLine() has the annoying habit of 
    // adding a \r\n to the end of the last line.  
    // Since we want a byte-for-byte transfer, we have to cut those chars.
    boolean rnflag = false;
    while ((result = in.readLine(bbuf, 0, bbuf.length)) != -1) {
      // Check for boundary
      if (result > 2 && bbuf[0] == '-' && bbuf[1] == '-') { // quick pre-check
        line = new String(bbuf, 0, result, "ISO-8859-1");
        if (line.startsWith(boundary)) break;
      }
      // Are we supposed to write \r\n for the last iteration?
      if (rnflag) {
        out.write('\r'); out.write('\n');
        rnflag = false;
      }
      // Write the buffer, postpone any ending \r\n
      if (result >= 2 && 
          bbuf[result - 2] == '\r' && 
          bbuf[result - 1] == '\n') {
        out.write(bbuf, 0, result - 2);  // skip the last 2 chars
        rnflag = true;  // make a note to write them on the next iteration
      }
      else {
        out.write(bbuf, 0, result);
      }
    }
    out.flush();
    out.close();
    fos.close();
  }

  // Extracts and returns the boundary token from a line.
  //
  private String extractBoundary(String line) {
    int index = line.indexOf("boundary=");
    if (index == -1) {
      return null;
    }
    String boundary = line.substring(index + 9);  // 9 for "boundary="

    // The real boundary is always preceeded by an extra "--"
    boundary = "--" + boundary;

    return boundary;
  }

  // Extracts and returns disposition info from a line, as a String array
  // with elements: disposition, name, filename.  Throws an IOException 
  // if the line is malformatted.
  //
  private String[] extractDispositionInfo(String line) throws IOException {
    // Return the line's data as an array: disposition, name, filename
    String[] retval = new String[3];

    // Convert the line to a lowercase string without the ending \r\n
    // Keep the original line for error messages and for variable names.
    String origline = line;
    line = origline.toLowerCase();

    // Get the content disposition, should be "form-data"
    int start = line.indexOf("content-disposition: ");
    int end = line.indexOf(";");
    if (start == -1 || end == -1) {
      throw new IOException("Content disposition corrupt: " + origline);
    }
    String disposition = line.substring(start + 21, end);
    if (!disposition.equals("form-data")) {
      throw new IOException("Invalid content disposition: " + disposition);
    }

    // Get the field name
    start = line.indexOf("name=\"", end);  // start at last semicolon
    end = line.indexOf("\"", start + 7);   // skip name=\"
    if (start == -1 || end == -1) {
      throw new IOException("Content disposition corrupt: " + origline);
    }
    String name = origline.substring(start + 6, end);

    // Get the filename, if given
    String filename = null;
    start = line.indexOf("filename=\"", end + 2);  // start after name
    end = line.indexOf("\"", start + 10);          // skip filename=\"
    if (start != -1 && end != -1) {                // note the !=
      filename = origline.substring(start + 10, end);
      // The filename may contain a full path.  Cut to just the filename.
      int slash =
        Math.max(filename.lastIndexOf('/'), filename.lastIndexOf('\\'));
      if (slash > -1) {
        filename = filename.substring(slash + 1);  // past last slash
      }
      if (filename.equals("")) filename = "unknown"; // sanity check
    }

    // Return a String array: disposition, name, filename
    retval[0] = disposition;
    retval[1] = name;
    retval[2] = filename;
    return retval;
  }

  // Extracts and returns the content type from a line, or null if the
  // line was empty.  Throws an IOException if the line is malformatted.
  //
  private String extractContentType(String line) throws IOException {
    String contentType = null;

    // Convert the line to a lowercase string
    String origline = line;
    line = origline.toLowerCase();

    // Get the content type, if any
    if (line.startsWith("content-type")) {
      int start = line.indexOf(" ");
      if (start == -1) {
        throw new IOException("Content type corrupt: " + origline);
      }
      contentType = line.substring(start + 1);
    }
    else if (line.length() != 0) {  // no content type, so should be empty
      throw new IOException("Malformed line after disposition: " + origline);
    }

    return contentType;
  }
}


// A class to hold information about an uploaded file.
//
class UploadedFile {

  private String dir;
  private String filename;
  private String type;

  UploadedFile(String dir, String filename, String type) {
    this.dir = dir;
    this.filename = filename;
    this.type = type;
  }

  public String getContentType() {
    return type;
  }

  public String getFilesystemName() {
    return filename;
  }

  public File getFile() {
    if (dir == null || filename == null) {
      return null;
    }
    else {
      return new File(dir + File.separator + filename);
    }
  }
}


// A class to aid in reading multipart/form-data from a ServletInputStream.
// It keeps track of how many bytes have been read and detects when the
// Content-Length limit has been reached.  This is necessary since some 
// servlet engines are slow to notice the end of stream.
//
// Mac users: The Mac doesn't like class names which exceed 32 characters
// (including the ".class") so while this class is usable from a JAR 
// anywhere, it won't compile on a Mac.
//
class MultipartInputStreamHandler {

  ServletInputStream in;
  int totalExpected;
  int totalRead = 0;
  byte[] buf = new byte[8 * 1024];

  public MultipartInputStreamHandler(ServletInputStream in,
                                     int totalExpected) {
    this.in = in;
    this.totalExpected = totalExpected;
  }

  // Reads the next line of input.  Returns null to indicate the end
  // of stream.
  //
  public String readLine() throws IOException {
    StringBuffer sbuf = new StringBuffer();
    int result;
    String line;

    do {
      result = this.readLine(buf, 0, buf.length);  // this.readLine() does +=
      if (result != -1) {
        sbuf.append(new String(buf, 0, result, "ISO-8859-1"));
      }
    } while (result == buf.length);  // loop only if the buffer was filled

    if (sbuf.length() == 0) {
      return null;  // nothing read, must be at the end of stream
    }

    sbuf.setLength(sbuf.length() - 2);  // cut off the trailing \r\n
    return sbuf.toString();
  }

  // A pass-through to ServletInputStream.readLine() that keeps track
  // of how many bytes have been read and stops reading when the 
  // Content-Length limit has been reached.
  //
  public int readLine(byte b[], int off, int len) throws IOException {
    if (totalRead >= totalExpected) {
      return -1;
    }
    else {
      int result = in.readLine(b, off, len);
      if (result > 0) {
        totalRead += result;
      }
      return result;
    }
  }
}