Class MultipartStream
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 := "--" boundary "--"
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
}
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionstatic classThrown upon attempt of setting an invalid boundary token.classAnInputStreamfor reading an items contents.static classThrown to indicate that the input stream fails to follow the required syntax.static classInternal class, which is used to invoke theProgressListener. -
Field Summary
FieldsModifier and TypeFieldDescriptionprotected static final byte[]A byte sequence that precedes a boundary (CRLF--).static final byteThe Carriage Return ASCII character value.static final byteThe dash (-) ASCII character value.protected static final intThe default length of the buffer used for processing a request.protected static final byte[]A byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF).static final intThe maximum length ofheader-partthat will be processed (10 kilobytes = 10240 bytes.).protected static final byte[]A byte sequence that marks the end ofheader-part(CRLFCRLF).static final byteThe Line Feed ASCII character value.protected static final byte[]A byte sequence that that follows a delimiter of the last encapsulation in the stream (--). -
Constructor Summary
ConstructorsConstructorDescriptionMultipartStream(InputStream input, byte[] boundary, int bufSize, MultipartStream.ProgressNotifier pNotifier) Constructs aMultipartStreamwith a custom size buffer.MultipartStream(InputStream input, byte[] boundary, MultipartStream.ProgressNotifier pNotifier) Constructs aMultipartStreamwith a default size buffer. -
Method Summary
Modifier and TypeMethodDescriptionstatic booleanarrayequals(byte[] a, byte[] b, int count) Comparescountfirst bytes in the arraysaandb.intReadsbody-datafrom the currentencapsulationand discards it.protected intSearches for theboundaryin thebufferregion delimited byheadandtail.Retrieves the character encoding used when reading the headers of an individual part.Creates a newMultipartStream.ItemInputStream.intreadBodyData(OutputStream output) Readsbody-datafrom the currentencapsulationand writes its contents into the outputStream.booleanSkips aboundarytoken, and checks whether moreencapsulationsare contained in the stream.bytereadByte()Reads a byte from thebuffer, and refills it as necessary.Reads theheader-partof the currentencapsulation.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.booleanFinds the beginning of the firstencapsulation.
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Field Details
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CR
public static final byte CRThe Carriage Return ASCII character value.- See Also:
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LF
public static final byte LFThe Line Feed ASCII character value.- See Also:
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DASH
public static final byte DASHThe dash (-) ASCII character value.- See Also:
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HEADER_PART_SIZE_MAX
public static final int HEADER_PART_SIZE_MAXThe maximum length ofheader-partthat will be processed (10 kilobytes = 10240 bytes.).- See Also:
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DEFAULT_BUFSIZE
protected static final int DEFAULT_BUFSIZEThe default length of the buffer used for processing a request.- See Also:
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HEADER_SEPARATOR
protected static final byte[] HEADER_SEPARATORA byte sequence that marks the end ofheader-part(CRLFCRLF). -
FIELD_SEPARATOR
protected static final byte[] FIELD_SEPARATORA byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF). -
STREAM_TERMINATOR
protected static final byte[] STREAM_TERMINATORA byte sequence that that follows a delimiter of the last encapsulation in the stream (--). -
BOUNDARY_PREFIX
protected static final byte[] BOUNDARY_PREFIXA byte sequence that precedes a boundary (CRLF--).
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Constructor Details
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MultipartStream
public MultipartStream(InputStream input, byte[] boundary, int bufSize, MultipartStream.ProgressNotifier pNotifier) Constructs a
MultipartStreamwith 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- TheInputStreamto 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.pNotifier- The notifier, which is used for calling the progress listener, if any.- Throws:
IllegalArgumentException- If the buffer size is too small- Since:
- FileUpload 1.3.1
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MultipartStream
public MultipartStream(InputStream input, byte[] boundary, MultipartStream.ProgressNotifier pNotifier) Constructs a
MultipartStreamwith a default size buffer.- Parameters:
input- TheInputStreamto serve as a data source.boundary- The token used for dividing the stream intoencapsulations.pNotifier- An object for calling the progress listener, if any.- See Also:
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Method Details
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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.
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setHeaderEncoding
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.
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readByte
Reads a byte from thebuffer, 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 FileUploadIOException, MultipartStream.MalformedStreamExceptionSkips aboundarytoken, and checks whether moreencapsulationsare contained in the stream.- Returns:
trueif there are more encapsulations in this stream;falseotherwise.- Throws:
FileUploadIOException- if the bytes read from the stream exceeded the size limitsMultipartStream.MalformedStreamException- if the stream ends unexpectedly or fails to follow required syntax.
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setBoundary
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
requiredto 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 theboundaryhas a different length than the one being currently parsed.
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readHeaders
Reads the
header-partof the currentencapsulation.Headers are returned verbatim to the input stream, including the trailing
CRLFmarker. Parsing is left to the application.TODO allow limiting maximum header size to protect against abuse.
- Returns:
- The
header-partof the current encapsulation. - Throws:
FileUploadIOException- if the bytes read from the stream exceeded the size limits.MultipartStream.MalformedStreamException- if the stream ends unexpectedly.
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readBodyData
public int readBodyData(OutputStream output) throws MultipartStream.MalformedStreamException, IOException Reads
body-datafrom the currentencapsulationand 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- TheStreamto write data into. May be null, in which case this method is equivalent todiscardBodyData().- 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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newInputStream
Creates a newMultipartStream.ItemInputStream.- Returns:
- A new instance of
MultipartStream.ItemInputStream.
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discardBodyData
Reads
body-datafrom the currentencapsulationand 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
Finds the beginning of the firstencapsulation.- Returns:
trueif anencapsulationwas 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) Comparescountfirst bytes in the arraysaandb.- Parameters:
a- The first array to compare.b- The second array to compare.count- How many bytes should be compared.- Returns:
trueifcountfirst bytes in arraysaandbare equal.
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findSeparator
protected int findSeparator()Searches for theboundaryin thebufferregion delimited byheadandtail.- Returns:
- The position of the boundary found, counting from the
beginning of the
buffer, or-1if not found.
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