portal.core.upload
Class MultipartStream

java.lang.Object
  portal.core.upload.MultipartStream

public class MultipartStream

extends java.lang.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 := "--" boudary "--"
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 exaple of usage of this class.

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

 

Version:

$Id: MultipartStream.java,v 1.3 2005/01/26 20:24:37 bavodr Exp $

Author:

Rafal Krzewski, Martin Cooper

Nested Class Summary

class	MultipartStream.IllegalBoundaryException Thrown upon attempt of setting an invalid boundary token.
class	MultipartStream.MalformedStreamException Thrown to indicate that the input stream fails to follow the required syntax.

Field Summary

protected static int	DEFAULT_BUFSIZE The default length of the buffer used for processing a request.
protected static byte[]	FIELD_SEPARATOR A byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF).
static int	HEADER_PART_SIZE_MAX The maximum length of header-part that will be processed (10 kilobytes = 10240 bytes.).
protected static byte[]	HEADER_SEPARATOR A byte sequence that marks the end of header-part (CRLFCRLF).
protected static byte[]	STREAM_TERMINATOR A byte sequence that that follows a delimiter of the last encapsulation in the stream (--).

Constructor Summary

MultipartStream()
Default constructor.

MultipartStream(java.io.InputStream input, byte[] boundary)
Constructs a MultipartStream with a default size buffer.

MultipartStream(java.io.InputStream input, byte[] boundary, int bufSize)
Constructs a MultipartStream with a custom size buffer.

Method Summary

static boolean	arrayequals(byte[] a, byte[] b, int count) Compares count first bytes in the arrays a and b.
int	discardBodyData() Reads body-data from the current encapsulation and discards it.
protected int	findByte(byte value, int pos) Searches for a byte of specified value in the buffer, starting at the specified position.
protected int	findSeparator() Searches for the boundary in the buffer region delimited by head and tail.
int	readBodyData(java.io.OutputStream output) Reads body-data from the current encapsulation and writes its contents into the output Stream.
boolean	readBoundary() Skips a boundary token, and checks whether more encapsulations are contained in the stream.
byte	readByte() Reads a byte from the buffer, and refills it as necessary.
java.lang.String	readHeaders() Reads the header-part of the current encapsulation.
void	setBoundary(byte[] boundary) Changes the boundary token used for partitioning the stream.
boolean	skipPreamble() Finds the beginning of the first encapsulation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

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:

Constant Field Values

DEFAULT_BUFSIZE

protected static final int DEFAULT_BUFSIZE

The default length of the buffer used for processing a request.

See Also:

Constant Field Values

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 (--).

Constructor Detail

MultipartStream

public MultipartStream()

Default constructor.

MultipartStream

public MultipartStream(java.io.InputStream input,
                       byte[] boundary,
                       int bufSize)

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.

MultipartStream

public MultipartStream(java.io.InputStream input,
                       byte[] boundary)
                throws java.io.IOException

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.

Throws:

java.io.IOException - when an error occurs.

Method Detail

readByte

public byte readByte()
              throws java.io.IOException

Reads a byte from the buffer, and refills it as necessary.

Returns:

The next byte from the input stream.

Throws:

java.io.IOException - if there is no more data available.

readBoundary

public boolean readBoundary()
                     throws 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:

MultipartStream.MalformedStreamException - if the stream ends unexpecetedly 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 java.lang.String readHeaders()
                             throws 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.

TO DO allow limiting maximum header size to protect against abuse.

Returns:

The header-part of the current encapsulation.

Throws:

MultipartStream.MalformedStreamException - if the stream ends unexpecetedly.

readBodyData

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

Returns:

the amount of data written.

Throws:

MultipartStream.MalformedStreamException - if the stream ends unexpectedly.

java.io.IOException - if an i/o error occurs.

discardBodyData

public int discardBodyData()
                    throws MultipartStream.MalformedStreamException,
                           java.io.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.

java.io.IOException - if an i/o error occurs.

skipPreamble

public boolean skipPreamble()
                     throws java.io.IOException

Finds the beginning of the first encapsulation.

Returns:

true if an encapsulation was found in the stream.

Throws:

java.io.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.

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.