org.apache.commons.fileupload
Class MultipartStream
java.lang.Object
org.apache.commons.fileupload.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:
- Rafal Krzewski
- Martin Cooper
- Sean C. Sullivan
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 (
-- ).
|
private byte[] | boundary - The byte sequence that partitions the stream.
|
private int | boundaryLength - The length of the boundary token plus the leading
CRLF-- .
|
private int | bufSize - The length of the buffer used for processing the request.
|
private byte[] | buffer - The buffer used for processing the request.
|
private int | head - The index of first valid character in the buffer.
|
private String | headerEncoding - The content encoding to use when reading headers.
|
private InputStream | input - The input stream from which data is read.
|
private int | keepRegion - The amount of data, in bytes, that must be kept in the buffer in order
to detect delimiters reliably.
|
private int | tail - The index of last valid characer in the buffer + 1.
|
MultipartStream() - Default constructor.
|
MultipartStream(InputStream input, byte[] boundary) - Constructs a
MultipartStream with a default size buffer.
|
MultipartStream(InputStream input, byte[] boundary, int bufSize) - Constructs a
MultipartStream with a custom size buffer.
|
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 .
|
String | getHeaderEncoding() - Retrieves the character encoding used when reading the headers of an
individual part.
|
int | readBodyData(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.
|
String | readHeaders() - Reads the
header-part of the current
encapsulation .
|
void | setBoundary(byte[] boundary) - Changes the boundary token used for partitioning the stream.
|
void | setHeaderEncoding(String encoding) - Specifies the character encoding to be used when reading the headers of
individual parts.
|
boolean | skipPreamble() - Finds the beginning of the first
encapsulation .
|
String | toString() - Returns a string representation of this object.
|
DEFAULT_BUFSIZE
protected static final int DEFAULT_BUFSIZE
The default length of the buffer used for processing a request.
- 4096
FIELD_SEPARATOR
protected static final byte[] FIELD_SEPARATOR
A byte sequence that that follows a delimiter that will be
followed by an encapsulation (CRLF
).
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.).
- 10240
HEADER_SEPARATOR
protected static final byte[] HEADER_SEPARATOR
A byte sequence that marks the end of header-part
(CRLFCRLF
).
STREAM_TERMINATOR
protected static final byte[] STREAM_TERMINATOR
A byte sequence that that follows a delimiter of the last
encapsulation in the stream (--
).
boundary
private byte[] boundary
The byte sequence that partitions the stream.
boundaryLength
private int boundaryLength
The length of the boundary token plus the leading CRLF--
.
bufSize
private int bufSize
The length of the buffer used for processing the request.
buffer
private byte[] buffer
The buffer used for processing the request.
head
private int head
The index of first valid character in the buffer.
0 <= head <32bufSize
headerEncoding
private String headerEncoding
The content encoding to use when reading headers.
input
private InputStream input
The input stream from which data is read.
keepRegion
private int keepRegion
The amount of data, in bytes, that must be kept in the buffer in order
to detect delimiters reliably.
tail
private int tail
The index of last valid characer in the buffer + 1.
0 <= tail <= bufSize
MultipartStream
public MultipartStream(InputStream input,
byte[] boundary)
throws IOException
Constructs a MultipartStream
with a default size buffer.
input
- The InputStream
to serve as a data source.boundary
- The token used for dividing the stream into
encapsulations
.
MultipartStream()
, MultipartStream(InputStream,byte[],int)
MultipartStream
public MultipartStream(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.
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()
, MultipartStream(InputStream,byte[])
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.
findByte
protected int findByte(byte value,
int pos)
Searches for a byte of specified value in the buffer
,
starting at the specified position
.
value
- The value to find.pos
- The starting position for searching.
- 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
.
- The position of the boundary found, counting from the
beginning of the
buffer
, or -1
if
not found.
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.
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
).
output
- The Stream
to write data into.
- the amount of data written.
MultipartStream.MalformedStreamException
- if the stream ends unexpectedly.
readByte
public byte readByte()
throws IOException
Reads a byte from the buffer
, and refills it as
necessary.
- The next byte from the input stream.
readHeaders
public 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.
TODO allow limiting maximum header size to
protect against abuse.
- The
header-part
of the current encapsulation.
MultipartStream.MalformedStreamException
- if the stream ends unexpecetedly.
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.
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.
skipPreamble
public boolean skipPreamble()
throws IOException
Finds the beginning of the first encapsulation
.
true
if an encapsulation
was found in
the stream.
toString
public String toString()
Returns a string representation of this object.
- The string representation of this object.
Copyright © 2002-2003 Apache Software Foundation. All Rights Reserved.