Class MultipartStream

http://www.devdaily.com/java/jwarehouse/commons-fileupload-1.0/src/java/org/apache/commons/fileupload/FileUploadBase.java.shtml



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

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Nested Class Summary
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.
static class MultipartStream.ProgressNotifier
          Internal class, which is used to invoke the ProgressListener.
  Field Summary
protected static byte[] BOUNDARY_PREFIX
          A byte sequence that precedes a boundary (CRLF--).
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).
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).
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 (--).
  Constructor Summary
MultipartStream()
          Deprecated. Use MultipartStream(InputStream, byte[], org.apache.commons.fileupload.MultipartStream.ProgressNotifier), or MultipartStream(InputStream, byte[], int, org.apache.commons.fileupload.MultipartStream.ProgressNotifier)
MultipartStream(InputStream input, byte[] boundary)
          Deprecated. Use MultipartStream(InputStream, byte[], MultipartStream.ProgressNotifier).
MultipartStream(InputStream input, byte[] boundary, int bufSize)
          Deprecated. Use MultipartStream(InputStream, byte[], int, org.apache.commons.fileupload.MultipartStream.ProgressNotifier).
  Method Summary
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.
  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 CRThe Carriage Return ASCII character value.

See Also:
Constant Field Values

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LF
public static final byte LFThe Line Feed ASCII character value.

See Also:
Constant Field Values

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DASH
public static final byte DASHThe dash (-) ASCII character value.

See Also:
Constant Field Values

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HEADER_PART_SIZE_MAX
public static final int HEADER_PART_SIZE_MAXThe maximum length of header-part that will be processed (10 kilobytes = 10240 bytes.).

See Also:
Constant Field Values

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

See Also:
Constant Field Values

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HEADER_SEPARATOR
protected static final byte[] HEADER_SEPARATORA byte sequence that marks the end of header-part (CRLFCRLF).


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FIELD_SEPARATOR
protected static final byte[] FIELD_SEPARATORA byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF).


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STREAM_TERMINATOR
protected static final byte[] STREAM_TERMINATORA byte sequence that that follows a delimiter of the last encapsulation in the stream (--).


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BOUNDARY_PREFIX
protected static final byte[] BOUNDARY_PREFIXA byte sequence that precedes a boundary (CRLF--).

Constructor Detail

MultipartStream
public MultipartStream()Deprecated. Use MultipartStream(InputStream, byte[], org.apache.commons.fileupload.MultipartStream.ProgressNotifier), or MultipartStream(InputStream, byte[], int, org.apache.commons.fileupload.MultipartStream.ProgressNotifier)

Creates a new instance.


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MultipartStream
public MultipartStream(InputStream input,
                       byte[] boundary,
                       int bufSize)Deprecated. Use MultipartStream(InputStream, byte[], int, org.apache.commons.fileupload.MultipartStream.ProgressNotifier).

Constructs a MultipartStream with a custom size buffer and no progress notifier.

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.ProgressNotifier)

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MultipartStream
public MultipartStream(InputStream input,
                       byte[] boundary)Deprecated. Use MultipartStream(InputStream, byte[], MultipartStream.ProgressNotifier).

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.
See Also:
MultipartStream(InputStream, byte[], int, MultipartStream.ProgressNotifier)
Method Detail

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.

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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.

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readByte
public byte readByte()
              throws IOExceptionReads 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.

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

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setBoundary
public void setBoundary(byte[] boundary)
                 throws MultipartStream.IllegalBoundaryExceptionChanges 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 the boundary has a different length than the one being currently parsed.

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readHeaders
public String readHeaders()
                   throws MultipartStream.MalformedStreamExceptionReads 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:
MultipartStream.MalformedStreamException - if the stream ends unexpecetedly.

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readBodyData
public int readBodyData(OutputStream output)
                 throws MultipartStream.MalformedStreamException,
                        IOExceptionReads 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).


Parameters:
output - The Stream to write data into. May be null, in which case this method is equivalent to discardBodyData().
Returns:
the amount of data written.
Throws:
MultipartStream.MalformedStreamException - if the stream ends unexpectedly.
IOException - if an i/o error occurs.

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discardBodyData
public int discardBodyData()
                    throws MultipartStream.MalformedStreamException,
                           IOExceptionReads 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:
MultipartStream.MalformedStreamException - if the stream ends unexpectedly.
IOException - if an i/o error occurs.

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skipPreamble
public boolean skipPreamble()
                     throws IOExceptionFinds the beginning of the first encapsulation.

Returns:
true if an encapsulation was found in the stream.
Throws:
IOException - if an i/o error occurs.

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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.

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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.

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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.