multipartparser.java

很好的文件处理程序

    // Read the headers; they look like this (not all may be present):
    // Content-Disposition: form-data; name="field1"; filename="file1.txt"
    // Content-Type: type/subtype
    // Content-Transfer-Encoding: binary
    Vector headers = new Vector();

    String line = readLine();
    if (line == null) {
      // No parts left, we're done
      return null;
    }
    else if (line.length() == 0) {
      // IE4 on Mac sends an empty line at the end; treat that as the end.
      // Thanks to Daniel Lemire and Henri Tourigny for this fix.
      return null;
    }

    // Read the following header lines we hit an empty line
    // A line starting with whitespace is considered a continuation;
    // that requires a little special logic.  Thanks to Nic Ferrier for
    // identifying a good fix.
    while (line != null && line.length() > 0) {
      String nextLine = null;
      boolean getNextLine = true;
      while (getNextLine) {
        nextLine = readLine();
        if (nextLine != null
            && (nextLine.startsWith(" ")
      	  || nextLine.startsWith("\t"))) {
          line = line + nextLine;
        }
        else {
          getNextLine = false;
        }
      }
      // Add the line to the header list
      headers.addElement(line);
      line = nextLine;
    }

    // If we got a null above, it's the end
    if (line == null) {
      return null;
    }

    String name = null;
    String filename = null;
    String origname = null;
    String contentType = "text/plain";  // rfc1867 says this is the default

    Enumeration enum = headers.elements();
    while (enum.hasMoreElements()) {
      String headerline = (String) enum.nextElement();
      if (headerline.toLowerCase().startsWith("content-disposition:")) {
        // Parse the content-disposition line
        String[] dispInfo = extractDispositionInfo(headerline);
        // String disposition = dispInfo[0];  // not currently used
        name = dispInfo[1];
        filename = dispInfo[2];
        origname = dispInfo[3];
      }
      else if (headerline.toLowerCase().startsWith("content-type:")) {
        // Get the content type, or null if none specified
        String type = extractContentType(headerline);
        if (type != null) {
          contentType = type;
        }
      }
    }

    // Now, finally, we read the content (end after reading the boundary)
    if (filename == null) {
      // This is a parameter, add it to the vector of values
      // The encoding is needed to help parse the value
      return new ParamPart(name, in, boundary, encoding);
    }
    else {
      // This is a file
      if (filename.equals("")) {
        filename = null; // empty filename, probably an "empty" file param
      }
      lastFilePart = new FilePart(name, in, boundary,
                                  contentType, filename, origname);
      return lastFilePart;
    }
  }
  
  /**
   * Extracts and returns the boundary token from a line.
   * 
   * @return the boundary token.
   */
  private String extractBoundary(String line) {
    // Use lastIndexOf() because IE 4.01 on Win98 has been known to send the
    // "boundary=" string multiple times.  Thanks to David Wall for this fix.
    int index = line.lastIndexOf("boundary=");
    if (index == -1) {
      return null;
    }
    String boundary = line.substring(index + 9);  // 9 for "boundary="
    if (boundary.charAt(0) == '"') {
      // The boundary is enclosed in quotes, strip them
      index = boundary.lastIndexOf('"');
      boundary = boundary.substring(1, index);
    }

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

    return boundary;
  }

  /**
   * Extracts and returns disposition info from a line, as a <code>String<code>
   * array with elements: disposition, name, filename.
   * 
   * @return String[] of elements: disposition, name, filename.
   * @exception  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[4];

    // 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=\"
    int startOffset = 6;
    if (start == -1 || end == -1) {
      // Some browsers like lynx don't surround with ""
      // Thanks to Deon van der Merwe, [e-mail], for noticing
      start = line.indexOf("name=", end);
      end = line.indexOf(";", start + 6);
      if (start == -1) {
        throw new IOException("Content disposition corrupt: " + origline);
      }
      else if (end == -1) {
        end = line.length();
      }
      startOffset = 5;  // without quotes we have one fewer char to skip
    }
    String name = origline.substring(start + startOffset, end);

    // Get the filename, if given
    String filename = null;
    String origname = 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);
      origname = filename;
      // 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
      }
    }

    // Return a String array: disposition, name, filename
    // empty filename denotes no file posted!
    retval[0] = disposition;
    retval[1] = name;
    retval[2] = filename;
    retval[3] = origname;
    return retval;
  }

  /**
   * Extracts and returns the content type from a line, or null if the
   * line was empty.
   * 
   * @return content type, or null if line was empty.
   * @exception  IOException if the line is malformatted.
   */
  private static String extractContentType(String line) throws IOException {
    // Convert the line to a lowercase string
    line = line.toLowerCase();

    // Get the content type, if any
    // Note that Opera at least puts extra info after the type, so handle
    // that.  For example:  Content-Type: text/plain; name="foo"
    // Thanks to Leon Poyyayil, [e-mail], for noticing this.
    int end = line.indexOf(";");
    if (end == -1) {
      end = line.length();
    }

    return line.substring(13, end).trim();  // "content-type:" is 13
  }
  
  /**
   * Read the next line of input.
   * 
   * @return     a String containing the next line of input from the stream,
   *        or null to indicate the end of the stream.
   * @exception IOException	if an input or output exception has occurred.
   */
  private String readLine() throws IOException {
    StringBuffer sbuf = new StringBuffer();
    int result;
    String line;

    do {
      result = in.readLine(buf, 0, buf.length);  // does +=
      if (result != -1) {
        sbuf.append(new String(buf, 0, result, encoding));
      }
    } 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
    }

    // Cut off the trailing \n or \r\n
    // It should always be \r\n but IE5 sometimes does just \n
    // Thanks to Luke Blaikie for helping make this work with \n
    int len = sbuf.length();
    if (len >= 2 && sbuf.charAt(len - 2) == '\r') {
      sbuf.setLength(len - 2);  // cut \r\n
    }
    else if (len >= 1 && sbuf.charAt(len - 1) == '\n') {
      sbuf.setLength(len - 1);  // cut \n
    }
    return sbuf.toString();
  }
}