This class represents a file or form item that was received within a
multipart/form-data POST request.
After retrieving an instance of this class from a FileUpload instance (see
#parseRequest(javax.servlet.http.HttpServletRequest) ), you may
either request all contents of the file at once using get() or
request an InputStream with
getInputStream() and process the file without attempting to load
it into memory, which may come handy with large files.
While this interface does not extend
javax.activation.DataSource per se (to avoid a seldom used
dependency), several of the defined methods are specifically defined with
the same signatures as methods in that interface. This allows an
implementation of this interface to also implement
javax.activation.DataSource with minimal additional work.