WSAttachments - PowerPoint PPT Presentation
1 / 24
Title: WSAttachments
1
WS-Attachments
- Yavuz Gürcan
- SRDC
2
OUTLINE
- Why do we need attachments?
- Limitations
- Requirements of WS-Attachments
- DIME
- Compound SOAP Message
- The Future of WS-Attachment
- MTOM
- Web Services Enhancements (WSE) 2.0
- Attachment Approaches
3
Why do we need attachments?
- There are situations where we would not want to
include the extra data within the original SOAP
message - That might occur when the format of the extra
data is unsuitable to conversion to XML, e.g.,
inefficient or bulky (as in media files, for
example) - Advantages
- Smaller message size
- Smaller memory requirements
- Smaller processing time (no need to convert
binary data to base-64) - Streaming
4
Limitations
- Encapsulation of binary data (in the form of
image files etc.) cannot be done without
additional encoding/decoding of the data. - Encapsulation of other XML documents as well as
XML fragments is cumbersome within a SOAP
message--especially if the XML parts do not use
the same character encoding. - Although SOAP messages inherently are
self-delimiting, the message delimiter can only
be detected by parsing the complete message. - SOAP with Attachments (SwA) addresses 1 and 2
- DIME is faster than MIME!
5
Requirements of WS-Attachments
- It is important that the packaging system provide
a mechanism for passing the different parts over
a single stream - A packaging solution must have
- The ability to separate where one part of the
package ends and the next part begins - It must have some mechanism for indicating when
the package is complete - A definitive mechanism for identifying each part
of a package - To be able to identify what kind of information
is in each part of the package
6
DIME - The Direct Internet Message Encapsulation
- DIME is a packaging mechanism that allows
multiple records of arbitrarily formatted data to
be streamed together - Records are serialized into the stream one after
the other and are delineated with an efficient
binary header - The first record in a DIME message has the MB
(Message Begin) flag set in the header and the
last record has the ME (Message End) flag set - The header also includes a fixed length-portion
that allows for the easy computation of the
absolute length of the record
7
DIME - Chunked records
- For large records or records where the size of
the data is not initially known, DIME has defined
a "record chunk - Each record chunk has a header and a payload like
normal records do, however a record chunk sets
the CF (Chunk Flag) in the header - This indicates that the data is part of a chunked
record and more data for that record will follow - The data for the chunked record is read serially
from the record chunks that follow until the last
record chunk is determined when the CF is no
longer set
8
DIME - Chunked records
9
DIME - Record Header
- The DIME record header includes
- The version of DIME that is being used
- Type of information about the data in the
record's payload - An ID to uniquely identify each record, and
- Support for adding any optional information that
may be transmitted with a particular record
10
Using DIME to Send a SOAP Message with Attachments
- DIME by itself is simply a mechanism for
packaging a collection of arbitrarily formatted
records of data - It sets no requirements on the contents of record
payloads, what is contained in the ID fields or
how a SOAP message might be encapsulated in a
DIME message
11
SOAP and DIME
- For SOAP messages with attachments, the main
message is referred to as the "Primary SOAP
Message Part - Any attached articles will be referred to as
"Secondary Parts" - WS-Attachments indicates that the Primary SOAP
Message Part must be contained in the first
record of a DIME message
12
SOAP and DIME
13
DIME - Referencing the Attachments
- WS-Attachments defines the use of the HREF
attribute for making such a reference - The HREF attribute is a URI that can be used to
point to an HTTP URL if so desired - But WS-Attachments also defines the ability to
refer to a specific DIME record using the ID
field of the DIME record header
14
DIME - Example
- If a secondary part of a DIME message had an ID
of - uuid6FF57C24-74A1-426f-92D9-98861E105B4F
- then the primary SOAP message part that
referenced such an attachment might be as
follows - lt?xml version'1.0' ?gt
- ltsEnvelope
- xmlnss"http//schemas.xmlsoap.org/soap/envel
ope/" - xmlnsmes"http//example.org/message/response
"gt - ltsBodygt ltmesresponseMesssagegt
- ltresponseTo
- href"uuid6FF57C24-74A1-426f-92D9-98861
E105B4F"/gt - ltmessageTextgtHello World!lt/messageTextgt
- lt/mesresponseMessagegt lt/sBodygt
lt/sEnvelopegt
15
DIME - Example
- The responseTo element in the message body has an
HREF attribute that specifies the ID of the DIME
record - Presumably the data in the DIME record is another
SOAP message that this message responds to - The receiver of this DIME message will not need
to track down the message that the primary SOAP
Message Part responds to, they simply can find it
in the specified secondary part of the DIME
message
16
Compound SOAP Message
- WS-Attachments also define the details of how a
compound SOAP message can be sent in an HTTP
request - For the most part it is similar to simply sending
the primary SOAP message part on its own, except
that the HTTP Content-Type header must be set to
"application/dime" and the body of the HTTP
request is the DIME message instead of the SOAP
message
17
The Future of WS-Attachment
- DIME is dead! )
- SOAP with attachments (multipart-mime, used by
JAX-RPC 1.1), and some optimizations known as
MTOM (first known as PASWA) won. - PASWA "Proposed Infoset Addendum to SOAP Messages
with Attachments", April 2003. http//www.gotdotne
t.com/team/jeffsch/paswa/paswa61.html - Limitation There is no support for attachments
when starting from Java. This is because for
certain Java types to MIME type mapping METADATA
support is needed. It will be supported in JAXRPC
2.0
18
MTOM (Message Transmission Optimization Mechanism)
- SOAP with Attachments and MTOM are based on MIME.
- MTOM goes a step further by including attachments
as part of the Infoset (since SOAP 1.2 is built
around Infoset), thus making the SOAP 1.2
processing model applicable to the attachments as
well. - MTOM is expected to be supported by JAXRPC 2.0
with SOAP 1.2 support. - W3C Working Draft 8 June 2004 http//www.w3.org/TR
/2004/WD-soap12-mtom-20040608/
19
Web Services Enhancements (WSE) 2.0 for Microsoft
.NET
- OASIS 2004 Specification
- Released 24 May 2004
- Messaging
- SOAP
- WS-Addressing
- MTOM (Attachments)
- WS-Eventing Â
20
Attachment Approaches
- XML Representation Replace any non-Xml data with
a structured XML representation and include it in
your message. - SOAP with Attachments (SwA) Use SOAP with
Attachments to send binary data with your SOAP in
a MIME Multipart message. - WS-Attachments with DIME Use DIME and
WS-Attachments to send binary data with your SOAP
in a DIME message format. - Base 64 Encoding Use base 64 encoding to include
opaque data within your SOAP message - Message Transmission and Optimization Mechanism
(MTOM) Use an MTOM approach to take advantage of
the SOAP infrastructure, but gain the transport
efficiencies provided by a SOAP with Attachments
solution.
21
XML Representation
- Interoperability Perfect
- Composability Excellent
- Efficiency Debatable
- When to use Whenever you can!
- ltpicturegt
- ltrowgt
- ltpixelgt
- ltcolorgt00FF00lt/colorgt
- lt/pixelgt
- ltpixelgt
- ltcolorgt00FF00lt/colorgt
22
SOAP with Attachments (SwA)
- Interoperability Perfect
- Composability Poor (cannot support WS-Security)
- Efficiency Good
- When to use If you never want to interoperate
with Microsoft platforms (.Net does not support
SwA)
23
WS-Attachments using DIME
- Interoperability Modest. Efforts for creating
widely interoperable DIME and WS-Attachment
implementations have stopped. As with SwA, there
is no recommendation for DIME or WS-Attachments
at this time. There are also no plans for
standardizing DIME and WS-Attachments. Microsoft
tools currently only support a DIME approach to
attachments, but will be changing to support MTOM
in the future. - Composability Poor
- Efficiency Very Good (has support for
efficiencies like chunking and jumping easily
between message records) - When to use Web services are all about
interoperability, and if DIME and WS-Attachments
does not provide wide interoperability. At this
point the only real reason to be using DIME and
WS-Attachments would be to interoperate with an
existing DIME and WS-Attachment implementation.
24
Base 64 Encoding
- Interoperability Excellent (Base-64-encoded data
is understood on every platform that understands
XML) - Composability Excellent (As data lives within
the SOAP envelope) - Efficiency Modest (bloats the data by about 33)
- When to use Base 64 encoding is probably the
best way to pass opaque data if transport size
efficiency is not your first concern
25
Message Transmission Optimization Mechanism
(MTOM)
- Interoperability Potentially great
- Composability Excellent
- Efficiency Excellent (Although the MIME
Multipart data transfer isn't quite as efficient
at transferring raw data as DIME, it can still
transfer data without additional bloating) - When to use You can probably expect to see MTOM
implementations in the third quarter of 2004.
Just be aware that you will probably need to
rebuild with the latest technology at some point
in the future.
Recommended
CrystalGraphics Presentations
