com.helger.web.multipart

Class MultipartStream

java.lang.Object

com.helger.web.multipart.MultipartStream

All Implemented Interfaces:

Serializable

public class MultipartStream
extends Object
implements Serializable

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 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
 }
 

Version:

$Id: MultipartStream.java 735374 2009-01-18 02:18:45Z jochen $

Author:

Rafal Krzewski, Martin Cooper, Sean C. Sullivan

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	MultipartStream.MultipartItemInputStream An InputStream for reading an items contents.

Field Summary

Fields

Modifier and Type	Field and Description
static byte	CR The Carriage Return ASCII character value.
static byte	DASH The dash (-) ASCII character value.
static int	HEADER_PART_SIZE_MAX The maximum length of header-part that will be processed (20 kilobytes = 10240 bytes.).
static byte	LF The Line Feed ASCII character value.

Constructor Summary

Constructors

Constructor and Description
MultipartStream(InputStream aIS, byte[] aBoundary, int nBufSize, MultipartProgressNotifier aNotifier) Constructs a MultipartStream with a custom size buffer.
MultipartStream(InputStream aIS, byte[] aBoundary, MultipartProgressNotifier aNotifier) Constructs a MultipartStream with a default size buffer.

Method Summary

Modifier and Type	Method and Description
MultipartStream.MultipartItemInputStream	createInputStream() Creates a new MultipartStream.MultipartItemInputStream.
int	discardBodyData() Reads body-data from the current encapsulation and discards it.
protected int	findByte(byte nValue, int nPos) 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.
String	getHeaderEncoding() Retrieves the character encoding used when reading the headers of an individual part.
int	readBodyData() 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.
String	readHeaders() Reads the header-part of the current encapsulation.
void	setBoundary(byte[] aBoundary) Changes the boundary token used for partitioning the stream.
void	setHeaderEncoding(String sHeaderEncoding) Specifies the character encoding to be used when reading the headers of individual parts.
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

CR

public static final byte CR

The Carriage Return ASCII character value.

See Also:

Constant Field Values

LF

public static final byte LF

The Line Feed ASCII character value.

See Also:

Constant Field Values

DASH

public static final byte DASH

The dash (-) ASCII character value.

See Also:

Constant Field Values

HEADER_PART_SIZE_MAX

public static final int HEADER_PART_SIZE_MAX

The maximum length of header-part that will be processed (20 kilobytes = 10240 bytes.).

See Also:

Constant Field Values

Constructor Detail

MultipartStream

public MultipartStream(InputStream aIS,
                       byte[] aBoundary,
                       int nBufSize,
                       MultipartProgressNotifier aNotifier)

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:

aIS - The InputStream to serve as a data source.

aBoundary - The token used for dividing the stream into encapsulations.

nBufSize - The size of the buffer to be used, in bytes.

aNotifier - The notifier, which is used for calling the progress listener, if any.

See Also:

MultipartStream(InputStream, byte[],MultipartProgressNotifier)

MultipartStream

public MultipartStream(InputStream aIS,
                       byte[] aBoundary,
                       MultipartProgressNotifier aNotifier)

Constructs a MultipartStream with a default size buffer.

Parameters:

aIS - The InputStream to serve as a data source.

aBoundary - The token used for dividing the stream into encapsulations.

aNotifier - An object for calling the progress listener, if any.

See Also:

MultipartStream(InputStream, byte[], int, MultipartProgressNotifier)

Method Detail

getHeaderEncoding

@Nullable
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(@Nullable
                              String sHeaderEncoding)

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:

sHeaderEncoding - 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 MultipartMalformedStreamException

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:

MultipartMalformedStreamException - if the stream ends unexpectedly or fails to follow required syntax.

setBoundary

public void setBoundary(@Nonnull
                        byte[] aBoundary)
                 throws MultipartIllegalBoundaryException

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:

aBoundary - The boundary to be used for parsing of the nested stream.

Throws:

MultipartIllegalBoundaryException - if the boundary has a different length than the one being currently parsed.

readHeaders

public String readHeaders()
                   throws MultipartMalformedStreamException

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.

Returns:

The header-part of the current encapsulation.

Throws:

MultipartMalformedStreamException - if the stream ends unexpectedly.

readBodyData

public int readBodyData()
                 throws 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 MultipartStream(InputStream, byte[], int, MultipartProgressNotifier) ).

Returns:

the amount of data read.

Throws:

MultipartMalformedStreamException - if the stream ends unexpectedly.

IOException - if an i/o error occurs.

createInputStream

@Nonnull
public MultipartStream.MultipartItemInputStream createInputStream()

Creates a new MultipartStream.MultipartItemInputStream.

Returns:

A new instance of MultipartStream.MultipartItemInputStream.

discardBodyData

public int discardBodyData()
                    throws 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:

MultipartMalformedStreamException - 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.

findByte

@CheckForSigned
protected int findByte(byte nValue,
                                        int nPos)

Searches for a byte of specified value in the buffer, starting at the specified position.

Parameters:

nValue - The value to find.

nPos - 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.