Class MultipartStream

  • public class MultipartStream
    extends Object

    Low level API for processing file uploads.

    This class can be used to process data streams conforming to MIME 'multipart' format as defined in RFC 1867. Arbitrarily large amounts of data in the stream can be processed under constant memory usage.

    The format of the stream is defined in the following way:
    multipart-body := preamble 1*encapsulation close-delimiter epilogue
    encapsulation := delimiter body CRLF
    delimiter := "--" boundary CRLF
    close-delimiter := "--" boundary "--"
    preamble := <ignore>
    epilogue := <ignore>
    body := header-part CRLF body-part
    header-part := 1*header CRLF
    header := header-name ":" header-value
    header-name := <printable ascii characters except ":">
    header-value := <any ascii characters except CR & LF>
    body-data := <arbitrary data>

    Note that body-data can contain another mulipart entity. There is limited support for single pass processing of such nested streams. The nested stream is required to have a boundary token of the same length as the parent stream (see setBoundary(byte[])).

    Here is an example of usage of this class.

       try {
         MultipartStream multipartStream = new MultipartStream(input, boundary);
         boolean nextPart = multipartStream.skipPreamble();
         OutputStream output;
         while(nextPart) {
           String header = multipartStream.readHeaders();
           // process headers
           // create some output stream
           nextPart = multipartStream.readBoundary();
       } catch(MultipartStream.MalformedStreamException e) {
         // the stream failed to follow required syntax
       } catch(IOException e) {
         // a read or write error occurred
    • Field Detail

      • CR

        public static final byte CR
        The Carriage Return ASCII character value.
        See Also:
        Constant Field Values
      • DASH

        public static final byte DASH
        The dash (-) ASCII character value.
        See Also:
        Constant Field Values

        public static final int HEADER_PART_SIZE_MAX
        The maximum length of header-part that will be processed (10 kilobytes = 10240 bytes.).
        See Also:
        Constant Field Values

        protected static final int DEFAULT_BUFSIZE
        The default length of the buffer used for processing a request.
        See Also:
        Constant Field Values

        protected static final byte[] HEADER_SEPARATOR
        A byte sequence that marks the end of header-part (CRLFCRLF).

        protected static final byte[] FIELD_SEPARATOR
        A byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF).

        protected static final byte[] STREAM_TERMINATOR
        A byte sequence that that follows a delimiter of the last encapsulation in the stream (--).

        protected static final byte[] BOUNDARY_PREFIX
        A byte sequence that precedes a boundary (CRLF--).
    • Constructor Detail

      • MultipartStream

        public MultipartStream​(InputStream input,
                               byte[] boundary,
                               int bufSize,
                               MultipartStream.ProgressNotifier pNotifier)

        Constructs a MultipartStream with a custom size buffer.

        Note that the buffer must be at least big enough to contain the boundary string, plus 4 characters for CR/LF and double dash, plus at least one byte of data. Too small a buffer size setting will degrade performance.

        input - The InputStream to serve as a data source.
        boundary - The token used for dividing the stream into encapsulations.
        bufSize - The size of the buffer to be used, in bytes.
        pNotifier - The notifier, which is used for calling the progress listener, if any.
        IllegalArgumentException - If the buffer size is too small
    • Method Detail

      • getHeaderEncoding

        public String getHeaderEncoding()
        Retrieves the character encoding used when reading the headers of an individual part. When not specified, or null, the platform default encoding is used.
        The encoding used to read part headers.
      • setHeaderEncoding

        public void setHeaderEncoding​(String encoding)
        Specifies the character encoding to be used when reading the headers of individual parts. When not specified, or null, the platform default encoding is used.
        encoding - The encoding used to read part headers.
      • readByte

        public byte readByte()
                      throws IOException
        Reads a byte from the buffer, and refills it as necessary.
        The next byte from the input stream.
        IOException - if there is no more data available.
      • setBoundary

        public void setBoundary​(byte[] boundary)
                         throws MultipartStream.IllegalBoundaryException

        Changes the boundary token used for partitioning the stream.

        This method allows single pass processing of nested multipart streams.

        The boundary token of the nested stream is required to be of the same length as the boundary token in parent stream.

        Restoring the parent stream boundary token after processing of a nested stream is left to the application.

        boundary - The boundary to be used for parsing of the nested stream.
        MultipartStream.IllegalBoundaryException - if the boundary has a different length than the one being currently parsed.
      • skipPreamble

        public boolean skipPreamble()
                             throws IOException
        Finds the beginning of the first encapsulation.
        true if an encapsulation was found in the stream.
        IOException - if an i/o error occurs.
      • arrayequals

        public static boolean arrayequals​(byte[] a,
                                          byte[] b,
                                          int count)
        Compares count first bytes in the arrays a and b.
        a - The first array to compare.
        b - The second array to compare.
        count - How many bytes should be compared.
        true if count first bytes in arrays a and b are equal.
      • findSeparator

        protected int findSeparator()
        Searches for the boundary in the buffer region delimited by head and tail.
        The position of the boundary found, counting from the beginning of the buffer, or -1 if not found.