org.apache.tomcat.util.http.fileupload

Class MultipartStream

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 (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 467222 2006-10-24 03:17:11Z markt $

Author: Rafal Krzewski Martin Cooper Sean C. Sullivan

Nested Class Summary
classMultipartStream.IllegalBoundaryException
Thrown upon attempt of setting an invalid boundary token.
classMultipartStream.MalformedStreamException
Thrown to indicate that the input stream fails to follow the required syntax.
Field Summary
protected static intDEFAULT_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 intHEADER_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(InputStream input, byte[] boundary, int bufSize)

Constructs a MultipartStream with a custom size buffer.

MultipartStream(InputStream input, byte[] boundary)

Constructs a MultipartStream with a default size buffer.

Method Summary
static booleanarrayequals(byte[] a, byte[] b, int count)
Compares count first bytes in the arrays a and b.
intdiscardBodyData()

Reads body-data from the current encapsulation and discards it.

protected intfindByte(byte value, int pos)
Searches for a byte of specified value in the buffer, starting at the specified position.
protected intfindSeparator()
Searches for the boundary in the buffer region delimited by head and tail.
StringgetHeaderEncoding()
Retrieves the character encoding used when reading the headers of an individual part.
intreadBodyData(OutputStream output)

Reads body-data from the current encapsulation and writes its contents into the output Stream.

booleanreadBoundary()
Skips a boundary token, and checks whether more encapsulations are contained in the stream.
bytereadByte()
Reads a byte from the buffer, and refills it as necessary.
StringreadHeaders()

Reads the header-part of the current encapsulation.

voidsetBoundary(byte[] boundary)

Changes the boundary token used for partitioning the stream.

voidsetHeaderEncoding(String encoding)
Specifies the character encoding to be used when reading the headers of individual parts.
booleanskipPreamble()
Finds the beginning of the first encapsulation.
StringtoString()
Returns a string representation of this object.

Field Detail

DEFAULT_BUFSIZE

protected static final int DEFAULT_BUFSIZE
The default length of the buffer used for processing a request.

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.).

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 (--).

Constructor Detail

MultipartStream

public MultipartStream()
Default constructor.

See Also: (InputStream, byte[], int) (InputStream, byte[])

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.

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.

See Also: MultipartStream (InputStream, byte[])

MultipartStream

public MultipartStream(InputStream input, byte[] boundary)

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: IOException when an error occurs.

See Also: MultipartStream (InputStream, byte[], int)

Method Detail

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.

discardBodyData

public int discardBodyData()

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: MalformedStreamException if the stream ends unexpectedly. IOException if an i/o error occurs.

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.

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.

Returns: The encoding used to read part headers.

readBodyData

public int readBodyData(OutputStream output)

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 (InputStream,byte[],int) constructor).

Parameters: output The Stream to write data into.

Returns: the amount of data written.

Throws: MalformedStreamException if the stream ends unexpectedly. IOException if an i/o error occurs.

readBoundary

public boolean readBoundary()
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: MalformedStreamException if the stream ends unexpecetedly or fails to follow required syntax.

readByte

public byte readByte()
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.

readHeaders

public String readHeaders()

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.

Returns: The header-part of the current encapsulation.

Throws: MalformedStreamException if the stream ends unexpecetedly.

setBoundary

public void setBoundary(byte[] boundary)

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: 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.

Parameters: encoding The encoding used to read part headers.

skipPreamble

public boolean skipPreamble()
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.

toString

public String toString()
Returns a string representation of this object.

Returns: The string representation of this object.

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