Transcript SOAP - CS Course Webpages

SOAP
CPSC 315 – Programming Studio
Spring 2008
Project 3, Lecture 2
XML Namespaces
• Different XML definitions could define
the same element name.
• If we want to use both, could have
conflict.
• Can distinguish using namespaces.
<a:book>…</a:book>
<b:book>…</b:book>
Defining XML Namespaces
• xmlns attribute in definition of element
xmlns:prefixname=“URL”
<a:book xmlns:a=http://this.com/adef>
• Can be defined in first use of element
or in XML root element.
• Can define a “default”
– No prefix needed, leave off : also
Middleware
• “Middle” layer between applications and
more basic system (OS)
• Provides a more common interface for
distributed applications
– Allows heterogeneous HW/OS platforms
• Generally refers to software allowing
processes running across network to
interact
SOAP
• Simple Object Access Protocol
• An XML-based message passing framework.
• Communicates via HTTP
– Enables easier communication around firewalls
• Applications can communicate using SOAP, even if in
different languages/operating systems
• Not the most efficient approach
– XML
– HTTP
• Full SOAP specifications are more generalized, not
necessarily as tied to HTTP
SOAP Messages
• XML Document
– Envelope element that encompasses document
• Optional header element
• Required Body element
– Optional Fault element
• Must use SOAP Envelope/Encoding namespaces
– Envelope:
• http://schemas.xmlsoap.org/soap/envelope/
• http://www.w3.org/2001/12/soap-envelope
– Encoding:
• http://schemas.xmlsoap.org/soap/encoding/
• http://www.w3.org/2001/12/soap-encoding
• No references to DTD or XML processing
SOAP Envelope
• Root element
<soap:Envelope
xmlns:soap=http://www.w3.org/2001/12/soapenvelope
soap:encodingStyle=http://www.w3.org/2001/12/so
ap-encoding
>
...
</soap:Envelope>
SOAP Header
• Idea is to give processing commands
• SOAP messages might pass through
many intermediate SOAP nodes
– These might process message in various
ways
– Header gives instructions on what the
receiving/relay/etc. node needs to do
– Header itself can change in this process.
SOAP Body
• The “main” message
• Must use namespace definitions to
specify elements.
<soap:Body>
<mq:GetTemp xlmns:mq=“http://this.com/temps”>
<mq:Location>Bryan</mq:Location>
<mq:Date>4/9/08</mq:date>
</mq:GetTemp>
<soap:Body>
SOAP Faults
• Occurs within Body element
– Several subelements possible
• faultcode
–
–
–
–
–
VersionMismatch
MustUnderstand
Client
Server
Can extend these (e.g. Client.Authentication)
• faultstring
– Human-readable explanation
• faultfactor
– Who caused the fault to happen
• detail
– Application-specific error information
More Information
• Official SOAP specifications:
http://www.w3.org/TR/soap/
(Discussed version 1.1)
http://www.w3.org/TR/2000/NOTE-SOAP20000508/
• SOAP tutorial:
http://www.w3schools.com/soap/default.asp