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 := "--" 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
   }
 | Modifier and Type | Class and Description | 
|---|---|
| static class  | MultipartStream.IllegalBoundaryExceptionThrown upon attempt of setting an invalid boundary token. | 
| class  | MultipartStream.ItemInputStreamAn  InputStreamfor reading an items contents. | 
| static class  | MultipartStream.MalformedStreamExceptionThrown to indicate that the input stream fails to follow the
 required syntax. | 
| static class  | MultipartStream.ProgressNotifierInternal class, which is used to invoke the
  ProgressListener. | 
| Modifier and Type | Field and Description | 
|---|---|
| protected static byte[] | BOUNDARY_PREFIXA byte sequence that precedes a boundary ( CRLF--). | 
| static byte | CRThe Carriage Return ASCII character value. | 
| static byte | DASHThe dash (-) ASCII character value. | 
| protected static int | DEFAULT_BUFSIZEThe default length of the buffer used for processing a request. | 
| protected static byte[] | FIELD_SEPARATORA byte sequence that that follows a delimiter that will be
 followed by an encapsulation ( CRLF). | 
| static int | HEADER_PART_SIZE_MAXThe maximum length of  header-partthat will be
 processed (10 kilobytes = 10240 bytes.). | 
| protected static byte[] | HEADER_SEPARATORA byte sequence that marks the end of  header-part(CRLFCRLF). | 
| static byte | LFThe Line Feed ASCII character value. | 
| protected static byte[] | STREAM_TERMINATORA byte sequence that that follows a delimiter of the last
 encapsulation in the stream ( --). | 
| Constructor and Description | 
|---|
| MultipartStream(InputStream input,
               byte[] boundary,
               int bufSize,
               MultipartStream.ProgressNotifier pNotifier) Constructs a  MultipartStreamwith a custom size buffer. | 
| MultipartStream(InputStream input,
               byte[] boundary,
               MultipartStream.ProgressNotifier pNotifier) Constructs a  MultipartStreamwith a default size buffer. | 
| Modifier and Type | Method and Description | 
|---|---|
| static boolean | arrayequals(byte[] a,
           byte[] b,
           int count)Compares  countfirst bytes in the arraysaandb. | 
| int | discardBodyData() Reads  body-datafrom the currentencapsulationand discards it. | 
| protected int | findByte(byte value,
        int pos)Searches for a byte of specified value in the  buffer,
 starting at the specifiedposition. | 
| protected int | findSeparator()Searches for the  boundaryin thebufferregion delimited byheadandtail. | 
| String | getHeaderEncoding()Retrieves the character encoding used when reading the headers of an
 individual part. | 
| MultipartStream.ItemInputStream | newInputStream()Creates a new  MultipartStream.ItemInputStream. | 
| int | readBodyData(OutputStream output)Reads  body-datafrom the currentencapsulationand writes its contents into the
 outputStream. | 
| boolean | readBoundary()Skips a  boundarytoken, and checks whether moreencapsulationsare contained in the stream. | 
| byte | readByte()Reads a byte from the  buffer, and refills it as
 necessary. | 
| String | readHeaders()Reads the  header-partof the currentencapsulation. | 
| 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.).protected static final int DEFAULT_BUFSIZE
protected static final byte[] HEADER_SEPARATOR
header-part
 (CRLFCRLF).protected static final byte[] FIELD_SEPARATOR
CRLF).protected static final byte[] STREAM_TERMINATOR
--).protected static final byte[] BOUNDARY_PREFIX
CRLF--).public MultipartStream(InputStream input, byte[] boundary, int bufSize, MultipartStream.ProgressNotifier pNotifier)
 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.
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.pNotifier - The notifier, which is used for calling the
                  progress listener, if any.IllegalArgumentException - If the buffer size is too smallpublic MultipartStream(InputStream input, byte[] boundary, MultipartStream.ProgressNotifier pNotifier)
 Constructs a MultipartStream with a default size buffer.
input - The InputStream to serve as a data source.boundary - The token used for dividing the stream into
                 encapsulations.pNotifier - An object for calling the progress listener, if any.MultipartStream(InputStream, byte[], int, ProgressNotifier)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 FileUploadIOException,
                            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.FileUploadIOException - if the bytes read from the stream exceeded the size limitsMultipartStream.MalformedStreamException - if the stream ends unexpectedly 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 FileUploadIOException, 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.FileUploadIOException - if the bytes read from the stream exceeded the size limits.MultipartStream.MalformedStreamException - if the stream ends unexpectedly.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 MultipartStream.ItemInputStream newInputStream()
MultipartStream.ItemInputStream.MultipartStream.ItemInputStream.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 © 2000-2020 Apache Software Foundation. All Rights Reserved.