Class MultipartInput

java.lang.Object
org.apache.commons.fileupload2.core.MultipartInput
public final class MultipartInput 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 {
    MultipartInput multipartStream = MultipartInput.builder()
            .setBoundary(boundary)
            .setInputStream(input)
            .get();
    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 (MultipartInput.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:

    • DEFAULT_PART_HEADER_SIZE_MAX

      public static final int DEFAULT_PART_HEADER_SIZE_MAX
      Default per part header size limit in bytes.
      Since:
      2.0.0-M4
      See Also:

  • Method Details

    • builder

      public static MultipartInput.Builder builder()
      Constructs a new MultipartInput.Builder.
      Returns:
      a new MultipartInput.Builder.

    • discardBodyData

      public long discardBodyData() throws MultipartInput.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:
      MultipartInput.MalformedStreamException - if the stream ends unexpectedly.
      IOException - if an i/o error occurs.

    • findByte

      protected int findByte(byte value, int pos)
      Searches for a byte of specified value in the buffer, starting at the specified position.
      Parameters:
      value - The value to find.
      pos - The starting position for searching.
      Returns:
      The position of byte found, counting from beginning of the buffer, or -1 if not found.

    • 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.

    • getHeaderCharset

      public Charset getHeaderCharset()
      Gets 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.

    • getMaxPartHeaderSize

      public int getMaxPartHeaderSize()
      Returns the per part size limit for headers.
      Returns:
      The maximum size of the headers in bytes.
      Since:
      2.0.0-M5

    • newInputStream

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

    • readBodyData

      public long readBodyData(OutputStream output) throws MultipartInput.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 builder()).

      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:
      MultipartInput.MalformedStreamException - if the stream ends unexpectedly.
      IOException - if an i/o error occurs.

    • readBoundary

      public boolean readBoundary() throws FileUploadSizeException, MultipartInput.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:
      FileUploadSizeException - if the bytes read from the stream exceeded the size limits
      MultipartInput.MalformedStreamException - if the stream ends unexpectedly or fails to follow required syntax.

    • 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.

    • readHeaders

      public String readHeaders() throws FileUploadSizeException, MultipartInput.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:
      FileUploadSizeException - if the bytes read from the stream exceeded the size limits.
      MultipartInput.MalformedStreamException - if the stream ends unexpectedly.

    • setBoundary

      public void setBoundary(byte[] boundary) throws MultipartInput.FileUploadBoundaryException
      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:
      MultipartInput.FileUploadBoundaryException - if the boundary has a different length than the one being currently parsed.

    • setHeaderCharset

      public void setHeaderCharset(Charset headerCharset)
      Sets 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:
      headerCharset - The encoding used to read part headers.

    • 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.