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public class: MultipartStream [javadoc | source]

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 exaple of usage of this class.

   try {
       MultipartStream multipartStream = new MultipartStream(input,
       boolean nextPart = malitPartStream.skipPreamble();
       OutputStream output;
       while(nextPart) {
           header = chunks.readHeader();
           // process headers
           // create some output stream
           nextPart = multipartStream.readBoundary();
   } catch(MultipartStream.MalformedStreamException e) {
         // the stream failed to follow required syntax
   } catch(IOException) {
         // a read or write error occurred

Nested Class Summary:
public class  MultipartStream.MalformedStreamException  Thrown to indicate that the input stream fails to follow the required syntax. 
public class  MultipartStream.IllegalBoundaryException  Thrown upon attempt of setting an invalid boundary token. 
Field Summary
public static final  int HEADER_PART_SIZE_MAX    The maximum length of header-part that will be processed (10 kilobytes = 10240 bytes.). 
protected static final  int DEFAULT_BUFSIZE    The default length of the buffer used for processing a request. 
protected static final  byte[] HEADER_SEPARATOR    A byte sequence that marks the end of header-part (CRLFCRLF). 
protected static final  byte[] FIELD_SEPARATOR    A byte sequence that that follows a delimiter that will be followed by an encapsulation (CRLF). 
protected static final  byte[] STREAM_TERMINATOR    A byte sequence that that follows a delimiter of the last encapsulation in the stream (--). 
 public MultipartStream() 
 public MultipartStream(InputStream input,
    byte[] boundary) throws IOException 

    Constructs a MultipartStream with a default size buffer.

 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.

Method from org.apache.tomcat.util.http.fileupload.MultipartStream Summary:
arrayequals,   discardBodyData,   findByte,   findSeparator,   getHeaderEncoding,   readBodyData,   readBoundary,   readByte,   readHeaders,   setBoundary,   setHeaderEncoding,   skipPreamble,   toString
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.apache.tomcat.util.http.fileupload.MultipartStream Detail:
 public static boolean arrayequals(byte[] a,
    byte[] b,
    int count) 
    Compares count first bytes in the arrays a and b.
 public int discardBodyData() throws 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.

 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.
 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.
 public int readBodyData(OutputStream output) throws 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 ).

 public boolean readBoundary() throws MalformedStreamException 
    Skips a boundary token, and checks whether more encapsulations are contained in the stream.
 public byte readByte() throws IOException 
    Reads a byte from the buffer, and refills it as necessary.
 public String readHeaders() throws 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.

 public  void setBoundary(byte[] boundary) throws 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.

 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.
 public boolean skipPreamble() throws IOException 
    Finds the beginning of the first encapsulation.
 public String toString() 
    Returns a string representation of this object.