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 example of usage of this class.
try { MultipartStream multipartStream = new MultipartStream(input, boundary); boolean nextPart = multipartStream.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 353822 2005-12-04 06:33:55Z martinc $
- Author:
- Rafal Krzewski, Martin Cooper, Sean C. Sullivan
-
-
Nested Class Summary
Nested Classes Modifier and Type Class Description static class
MultipartStream.IllegalBoundaryException
Thrown upon attempt of setting an invalid boundary token.static class
MultipartStream.MalformedStreamException
Thrown to indicate that the input stream fails to follow the required syntax.
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Field Summary
Fields Modifier and Type Field Description private byte[]
boundary
The byte sequence that partitions the stream.protected static byte[]
BOUNDARY_PREFIX
A byte sequence that precedes a boundary (CRLF--
).private int
boundaryLength
The length of the boundary token plus the leadingCRLF--
.private byte[]
buffer
The buffer used for processing the request.private int
bufSize
The length of the buffer used for processing the request.static byte
CR
The Carriage Return ASCII character value.static byte
DASH
The dash (-) ASCII character value.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
).private int
head
The index of first valid character in the buffer.static int
HEADER_PART_SIZE_MAX
The maximum length ofheader-part
that will be processed (10 kilobytes = 10240 bytes.).protected static byte[]
HEADER_SEPARATOR
A byte sequence that marks the end ofheader-part
(CRLFCRLF
).private java.lang.String
headerEncoding
The content encoding to use when reading headers.private java.io.InputStream
input
The input stream from which data is read.private static int
KEEP_REGION_PAD
The number of bytes, over and above the boundary size, to use for the keep region.private int
keepRegion
The amount of data, in bytes, that must be kept in the buffer in order to detect delimiters reliably.static byte
LF
The Line Feed ASCII character value.protected static byte[]
STREAM_TERMINATOR
A byte sequence that that follows a delimiter of the last encapsulation in the stream (--
).private int
tail
The index of last valid characer in the buffer + 1.
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Constructor Summary
Constructors Constructor Description MultipartStream()
Default constructor.MultipartStream(java.io.InputStream input, byte[] boundary)
Constructs aMultipartStream
with a default size buffer.MultipartStream(java.io.InputStream input, byte[] boundary, int bufSize)
Constructs aMultipartStream
with a custom size buffer.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static boolean
arrayequals(byte[] a, byte[] b, int count)
Comparescount
first bytes in the arraysa
andb
.int
discardBodyData()
Readsbody-data
from the currentencapsulation
and discards it.protected int
findByte(byte value, int pos)
Searches for a byte of specified value in thebuffer
, starting at the specifiedposition
.protected int
findSeparator()
Searches for theboundary
in thebuffer
region delimited byhead
andtail
.java.lang.String
getHeaderEncoding()
Retrieves the character encoding used when reading the headers of an individual part.int
readBodyData(java.io.OutputStream output)
Readsbody-data
from the currentencapsulation
and writes its contents into the outputStream
.boolean
readBoundary()
Skips aboundary
token, and checks whether moreencapsulations
are contained in the stream.byte
readByte()
Reads a byte from thebuffer
, and refills it as necessary.java.lang.String
readHeaders()
Reads theheader-part
of the currentencapsulation
.void
setBoundary(byte[] boundary)
Changes the boundary token used for partitioning the stream.void
setHeaderEncoding(java.lang.String encoding)
Specifies the character encoding to be used when reading the headers of individual parts.boolean
skipPreamble()
Finds the beginning of the firstencapsulation
.java.lang.String
toString()
Returns a string representation of this object.
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-
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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 ofheader-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 ofheader-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--
).
-
KEEP_REGION_PAD
private static final int KEEP_REGION_PAD
The number of bytes, over and above the boundary size, to use for the keep region.- See Also:
- Constant Field Values
-
input
private java.io.InputStream input
The input stream from which data is read.
-
boundaryLength
private int boundaryLength
The length of the boundary token plus the leadingCRLF--
.
-
keepRegion
private int keepRegion
The amount of data, in bytes, that must be kept in the buffer in order to detect delimiters reliably.
-
boundary
private byte[] boundary
The byte sequence that partitions the stream.
-
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 < bufSize
-
tail
private int tail
The index of last valid characer in the buffer + 1.
0 <= tail <= bufSize
-
headerEncoding
private java.lang.String headerEncoding
The content encoding to use when reading headers.
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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
- TheInputStream
to serve as a data source.boundary
- The token used for dividing the stream intoencapsulations
.bufSize
- The size of the buffer to be used, in bytes.- See Also:
MultipartStream()
,MultipartStream(InputStream, byte[])
-
MultipartStream
public MultipartStream(java.io.InputStream input, byte[] boundary) throws java.io.IOException
Constructs a
MultipartStream
with a default size buffer.- Parameters:
input
- TheInputStream
to serve as a data source.boundary
- The token used for dividing the stream intoencapsulations
.- Throws:
java.io.IOException
- when an error occurs.- See Also:
MultipartStream()
,MultipartStream(InputStream, byte[], int)
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Method Detail
-
getHeaderEncoding
public java.lang.String getHeaderEncoding()
Retrieves the character encoding used when reading the headers of an individual part. When not specified, ornull
, the platform default encoding is used.- Returns:
- The encoding used to read part headers.
-
setHeaderEncoding
public void setHeaderEncoding(java.lang.String encoding)
Specifies the character encoding to be used when reading the headers of individual parts. When not specified, ornull
, the platform default encoding is used.- Parameters:
encoding
- The encoding used to read part headers.
-
readByte
public byte readByte() throws java.io.IOException
Reads a byte from thebuffer
, 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 aboundary
token, and checks whether moreencapsulations
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 theboundary
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 currentencapsulation
.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:
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 currentencapsulation
and writes its contents into the outputStream
.Arbitrary large amounts of data can be processed by this method using a constant size buffer. (see
constructor
).- Parameters:
output
- TheStream
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 currentencapsulation
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.
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skipPreamble
public boolean skipPreamble() throws java.io.IOException
Finds the beginning of the firstencapsulation
.- Returns:
true
if anencapsulation
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)
Comparescount
first bytes in the arraysa
andb
.- Parameters:
a
- The first array to compare.b
- The second array to compare.count
- How many bytes should be compared.- Returns:
true
ifcount
first bytes in arraysa
andb
are equal.
-
findByte
protected int findByte(byte value, int pos)
Searches for a byte of specified value in thebuffer
, starting at the specifiedposition
.- 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 theboundary
in thebuffer
region delimited byhead
andtail
.- Returns:
- The position of the boundary found, counting from the
beginning of the
buffer
, or-1
if not found.
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toString
public java.lang.String toString()
Returns a string representation of this object.- Overrides:
toString
in classjava.lang.Object
- Returns:
- The string representation of this object.
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