Package org.apache.tomcat.util.http.fileupload

Class MultipartStream

java.lang.Object
org.apache.tomcat.util.http.fileupload.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
       multipartStream.readBodyData(output);
       nextPart = multipartStream.readBoundary();
     }
   } catch(MultipartStream.MalformedStreamException e) {
     // the stream failed to follow required syntax
   } catch(IOException e) {
     // a read or write error occurred
   }

  • Field Details

    • CR

      public static final byte CR
      The Carriage Return ASCII character value.
      See Also:

    • LF

      public static final byte LF
      The Line Feed ASCII character value.
      See Also:

    • DASH

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

    • HEADER_PART_SIZE_MAX

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

    • DEFAULT_BUFSIZE

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

    • HEADER_SEPARATOR

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

    • FIELD_SEPARATOR

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

    • STREAM_TERMINATOR

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

    • BOUNDARY_PREFIX

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

  • Constructor Details

    • 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.

      Parameters:
      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.
      Throws:
      IllegalArgumentException - If the buffer size is too small
      Since:
      FileUpload 1.3.1

    • MultipartStream

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

      Constructs a MultipartStream with a default size buffer.

      Parameters:
      input - The InputStream to serve as a data source.
      boundary - The token used for dividing the stream into encapsulations.
      pNotifier - An object for calling the progress listener, if any.
      See Also:

  • Method Details

    • 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.
      Returns:
      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.
      Parameters:
      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.
      Returns:
      The next byte from the input stream.
      Throws:
      IOException - if there is no more data available.

    • readBoundary

      public boolean readBoundary() throws FileUploadIOException, MultipartStream.MalformedStreamException
      Skips a boundary token, and checks whether more encapsulations are contained in the stream.
      Returns:
      true if there are more encapsulations in this stream; false otherwise.
      Throws:
      FileUploadIOException - if the bytes read from the stream exceeded the size limits
      MultipartStream.MalformedStreamException - if the stream ends unexpectedly or fails to follow required syntax.

    • 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.

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

    • readHeaders

      public String readHeaders() throws FileUploadIOException, MultipartStream.MalformedStreamException

      Reads the header-part of the current encapsulation.

      Headers are returned verbatim to the input stream, including the trailing CRLF marker. Parsing is left to the application.

      TODO allow limiting maximum header size to protect against abuse.

      Returns:
      The header-part of the current encapsulation.
      Throws:
      FileUploadIOException - if the bytes read from the stream exceeded the size limits.
      MultipartStream.MalformedStreamException - if the stream ends unexpectedly.

    • readBodyData

      public int readBodyData(OutputStream output) throws MultipartStream.MalformedStreamException, IOException

      Reads body-data from the current encapsulation and writes its contents into the output Stream.

      Arbitrary large amounts of data can be processed by this method using a constant size buffer. (see constructor).

      Parameters:
      output - The Stream to write data into. May be null, in which case this method is equivalent to discardBodyData().
      Returns:
      the amount of data written.
      Throws:
      MultipartStream.MalformedStreamException - if the stream ends unexpectedly.
      IOException - if an i/o error occurs.

    • newInputStream

      public MultipartStream.ItemInputStream newInputStream()
      Creates a new MultipartStream.ItemInputStream.
      Returns:
      A new instance of MultipartStream.ItemInputStream.

    • discardBodyData

      public int discardBodyData() throws MultipartStream.MalformedStreamException, IOException

      Reads body-data from the current encapsulation and discards it.

      Use this method to skip encapsulations you don't need or don't understand.

      Returns:
      The amount of data discarded.
      Throws:
      MultipartStream.MalformedStreamException - if the stream ends unexpectedly.
      IOException - if an i/o error occurs.

    • skipPreamble

      public boolean skipPreamble() throws IOException
      Finds the beginning of the first encapsulation.
      Returns:
      true if an encapsulation was found in the stream.
      Throws:
      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.
      Parameters:
      a - The first array to compare.
      b - The second array to compare.
      count - How many bytes should be compared.
      Returns:
      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.
      Returns:
      The position of the boundary found, counting from the beginning of the buffer, or -1 if not found.