public class MultipartStream 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 := "--" 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
}
| Modifier and Type | Class and Description |
|---|---|
static class |
MultipartStream.IllegalBoundaryException
Thrown upon attempt of setting an invalid boundary token.
|
class |
MultipartStream.ItemInputStream
An
InputStream for reading an items contents. |
static class |
MultipartStream.MalformedStreamException
Thrown to indicate that the input stream fails to follow the
required syntax.
|
| 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 (10 kilobytes = 10240 bytes.). |
static byte |
LF
The Line Feed ASCII character value.
|
| Modifier and Type | Method and Description |
|---|---|
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. |
public static final byte CR
public static final byte LF
public static final byte DASH
public static final int HEADER_PART_SIZE_MAX
header-part that will be
processed (10 kilobytes = 10240 bytes.).public String getHeaderEncoding()
null, the platform
default encoding is used.public void setHeaderEncoding(String encoding)
null, the platform
default encoding is used.encoding - The encoding used to read part headers.public byte readByte()
throws IOException
buffer, and refills it as
necessary.IOException - if there is no more data available.public boolean readBoundary()
throws MultipartStream.MalformedStreamException
boundary token, and checks whether more
encapsulations are contained in the stream.true if there are more encapsulations in
this stream; false otherwise.MultipartStream.MalformedStreamException - if the stream ends unexpecetedly or
fails to follow required syntax.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.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.
header-part of the current encapsulation.MultipartStream.MalformedStreamException - if the stream ends unexpecetedly.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. May
be null, in which case this method is equivalent
to discardBodyData().MultipartStream.MalformedStreamException - if the stream ends unexpectedly.IOException - if an i/o error occurs.public int discardBodyData()
throws MultipartStream.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.
MultipartStream.MalformedStreamException - if the stream ends unexpectedly.IOException - if an i/o error occurs.public boolean skipPreamble()
throws IOException
encapsulation.true if an encapsulation was found in
the stream.IOException - if an i/o error occurs.public static boolean arrayequals(byte[] a,
byte[] b,
int count)
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.protected int findByte(byte value,
int pos)
buffer,
starting at the specified position.value - The value to find.pos - The starting position for searching.buffer, or -1 if not found.protected int findSeparator()
boundary in the buffer
region delimited by head and tail.buffer, or -1 if
not found.Copyright © 2020. All rights reserved.