This defines a reusable datasource that can supply an input stream with
MimeMessage data. This allows a MimeMessageWrapper or other classes to
grab the underlying data.
See Also:MimeMessageWrapper
Get an input stream to retrieve the data stored in the datasource
a InputStream containing the data throws: IOException - if an error occurs while generating theInputStream
Return the size of all the data.
Default implementation... others can override to do this much faster
the size of the data represented by this source throws: IOException - if an error is encountered while computing the message size
Returns a unique String ID that represents the location from where
this file is loaded. This will be used to identify where the data
is, primarily to avoid situations where this data would get overwritten.
the String ID