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(SQL Server) MIME Body vs. Sub-Parts
Explains the difference between sub-parts and body.
MIME documents (i.e. messages) can have a nested structure. The simplest MIME message contains a header followed by content (possibly encoded). The header is delimited from the content by two consecutive CRLF's.
A MIME message may be multipart. If so, then the Content-Type header field indicates "multipart" and the content the follows the header is itself a MIME message, which may also be multipart, etc. You can see how MIME messages effectively have a tree structure. The non-leaf nodes have Content-Types that are "multipart/" and the leaf nodes have non-multipart Content-Types.
The Chilkat MIME component/library uses two terms that need to be understood in order to effectively use the API. These are "body" and "sub-part". A multipart node has 1 or more sub-parts, but its body is empty. A leaf node (i.e. non-multipart node) has no sub-parts, but the body is (usually) non-empty.
This example creates a multipart MIME message and shows the results of getting the sub-parts and body of each node.
-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
DECLARE @hr int
-- Important: Do not use nvarchar(max). See the warning about using nvarchar(max).
DECLARE @sTmp0 nvarchar(4000)
-- This example assumes the Chilkat API to have been previously unlocked.
-- See Global Unlock Sample for sample code.
DECLARE @mime int
-- Use "Chilkat_9_5_0.Mime" for versions of Chilkat < 10.0.0
EXEC @hr = sp_OACreate 'Chilkat.Mime', @mime OUT
IF @hr <> 0
BEGIN
PRINT 'Failed to create ActiveX component'
RETURN
END
-- Create a multipart/mixed MIME message with two sub-parts.
-- We'll use the Base64 encoding for the 2nd sub-part.
DECLARE @part1 int
-- Use "Chilkat_9_5_0.Mime" for versions of Chilkat < 10.0.0
EXEC @hr = sp_OACreate 'Chilkat.Mime', @part1 OUT
DECLARE @success int
EXEC sp_OAMethod @part1, 'SetBodyFromPlainText', @success OUT, 'This is part 1'
DECLARE @part2 int
-- Use "Chilkat_9_5_0.Mime" for versions of Chilkat < 10.0.0
EXEC @hr = sp_OACreate 'Chilkat.Mime', @part2 OUT
EXEC sp_OAMethod @part2, 'SetBodyFromPlainText', @success OUT, 'This is part 2'
EXEC sp_OASetProperty @part2, 'Encoding', 'base64'
EXEC sp_OAMethod @mime, 'NewMultipartMixed', @success OUT
EXEC sp_OASetProperty @mime, 'UseMmDescription', 0
EXEC sp_OAMethod @mime, 'AppendPart', @success OUT, @part1
EXEC sp_OAMethod @mime, 'AppendPart', @success OUT, @part2
-- Show the MIME message:
EXEC sp_OAMethod @mime, 'GetMime', @sTmp0 OUT
PRINT @sTmp0
-- Here's the MIME:
-- Content-Type: multipart/mixed;
-- boundary="------------040605030407000302060008"
--
-- --------------040605030407000302060008
-- Content-Type: text/plain;
-- charset="us-ascii"
-- Content-Transfer-Encoding: 7bit
--
-- This is part 1
-- --------------040605030407000302060008
-- Content-Type: text/plain;
-- charset="us-ascii"
-- Content-Transfer-Encoding: base64
--
-- VGhpcyBpcyBwYXJ0IDI=
--
-- --------------040605030407000302060008--
-- If we examine the root node of the MIME message,
-- we see that it has 2 sub-parts and the body is empty (as expected)
DECLARE @n int
EXEC sp_OAGetProperty @mime, 'NumParts', @n OUT
PRINT 'Num Parts = ' + @n
EXEC sp_OAMethod @mime, 'GetBodyDecoded', @sTmp0 OUT
PRINT 'Body = ' + @sTmp0
-- The GetEntireBody retrieves the entire content after
-- the header. (Perhaps GetEntireBody should've been named
-- GetEntireContent to make it less confusing...)
PRINT '---- EntireBody:'
EXEC sp_OAMethod @mime, 'GetEntireBody', @sTmp0 OUT
PRINT @sTmp0
PRINT '********'
-- Now examine the 2nd sub-part. It has a body encoded
-- using base64. Get the contents of the body in both
-- decoded and encoded forms:
DECLARE @part int
-- index 0 is the 1st part, index 1 is the 2nd part.
EXEC sp_OAMethod @mime, 'GetPart', @part OUT, 1
PRINT 'Decoded Body:'
EXEC sp_OAMethod @part, 'GetBodyDecoded', @sTmp0 OUT
PRINT @sTmp0
PRINT 'Encoded Body:'
EXEC sp_OAMethod @part, 'GetBodyEncoded', @sTmp0 OUT
PRINT @sTmp0
EXEC @hr = sp_OADestroy @part
EXEC @hr = sp_OADestroy @mime
EXEC @hr = sp_OADestroy @part1
EXEC @hr = sp_OADestroy @part2
END
GO
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