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Web Services: SOAP
SOAP
• SOAP ir standarts Web servisu saziņošanas
protokols
• Oriģināli SOAP nozīmēja
•
Simple Object Access Protocol
vēlāk arī
•
Service Oriented Architecture Protocol
bet sākot ar versiju 1.2 tas ir vienkārši SOAP
Vēsture un versijas
• SOAP 1998. gadā izstrādāja Dave Winer, Don
Box, Bob Atkinson un Mohsen Al-Ghosein
• SOAP 1.1 – W3C ierosinājums 2000.gada maijā
•
J2EE 1.4 standarts
• SOAP 1.2 – W3C rekomendācija sākot ar
2003.gada jūniju
•
Java EE 5 standarts
Kas ir SOAP?
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SOAP is a communication protocol
SOAP is for communication between applications
SOAP is a format for sending messages
SOAP is designed to communicate via Internet
SOAP is platform independent
SOAP is language independent
SOAP is based on XML
SOAP is simple and extensible
SOAP allows you to get around firewalls
SOAP is developed as a W3C standard
Kas SOAP nav?
• SOAP nav komponentu modelis
• Tas neaizvietos objektus un
komponentus, piemērām EJB,
JavaBeans
• SOAP nav programmēšanas valoda
• Tas neaizvietos Java valodu
• SOAP nav risinājums visiem
uzdevumiem
• Tas neaizvietos citas dalītas apstrādes
Kāpēc SOAP?
• Izstrādājot lietojumprogrammas ir svarīgi dot
iespēju programmām sazināties pa Internetu
• Viens sazināšanas veids ir RPC (Remote
Procedure Call), bet HTTP nav īsti piemērots
šīm variantam
• SOAP bija izveidots, lai nodrošināt iespēju
sazināties pa HTTP (kaut gan var tikt
izmantots arī cits protokols, piemēram SMTP)
SOAP over HTTP, SMTP, and
Raw TCP/IP
A SOAP XML document instance, which is called a SOAP
message, is usually carried as the payload of some other
network protocol
One-Way versus Request/Response
• Web services can use
One-Way messaging or
Request/Response messaging
Ko SOAP definē?
• Message Envelope
• Encoding Rules
• RPC Convention
• Binding with underlying protocols
SOAP Message
• SOAP message is made of
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SOAP Envelope (in XML)
Zero or more attachments
Zero or more "underlying protocol" header fields
• SOAP Envelope is composed of
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SOAP body
• Main content of the message
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Zero or more SOAP header blocks
• Metadata
• Data aimed at intermediaries
• Can also contain application data for ultimate receiver
SOAP Message Format
SOAP in HTTP Request
HTTP Request
HTTP Body
XML Syntax
SOAP Envelope
SOAP Body
SOAP Body Block
Textual Integer
Sender
0x0b66
Receiver
SOAP Message Structure
• A SOAP message is analogous to an envelope
used in traditional postal service
• A SOAP message is a kind of XML document
• SOAP has its own XML schema, namespaces,
and processing rules
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Header>

</soap:Header>
<soap:Body>

</soap:Body>
</soap:Envelope>
SOAP Message Structure
• A SOAP message may have a single Body
element preceded, optionally, by one Header
element
• The Envelope element cannot contain any
other children!
• The Header element contains information about
the message:
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security credentials
transaction IDs
routing instructions
debugging information
payment tokens
Example: SOAP Header
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:mi="http://www.Monson-Haefel.com/message-id">
<soap:Header>
<mi:message-id>
11d1def534ea:b1c5fa:f3bfb4dcd7:-8000
</mi:message-id>
</soap:Header>
<soap:Body>

</soap:Body>
</soap:Envelope>
SOAP Namespaces
• XML namespaces play an important role in SOAP
messages
• Examples of namespace prefixes:
Prefix
Namespace
soap
"http://schemas.xmlsoap.org/soap/envelope/"
xsi
"http://www.w3.org/2001/XMLSchema-instance"
xsd
"http://www.w3.org/2001/XMLSchema"
soapenc
"http://schemas.xmlsoap.org/soap/encoding/"
wsdl
"http://schemas.xmlsoap.org/wsdl/"
soapbind
"http://schemas.xmlsoap.org/wsdl/soap/"
wsi
"http://ws-i.org/schemas/conformanceClaim/"
Example: SOAP Namespaces
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:sec="http://schemas.xmlsoap.org/soap/security/2000-12"
xmlns:ds="http://www.w3.org/2000/09/xmldsig#"
xmlns:mi="http://www.Monson-Haefel.com/jwsbook/message-id">
<soap:Header>
<mi:message-id>11d1def534ea:b1c5fa:f3bfb4dcd7:-8000</mi:message-id>
<sec:Signature> ... </sec:Signature>
</soap:Header>
<soap:Body sec:id="Body">
<po:purchaseOrder orderDate="2003-09-22"
xmlns:po="http://www.Monson-Haefel.com/jwsbook/PO"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
...
</po:purchaseOrder>
</soap:Body>
</soap:Envelope>
SOAP Message Path
• Initial sender creates message
• Ultimate receiver executes main operation
• Intermediaries perform additional processing
SOAP Nodes
• The applications along the message path are also
called SOAP nodes
Initial sender
Security intermediary
Final receiver
• Example:
•
security node authenticates users and verifies
message integrity
• SOAP message Header blocks are intended to
be processed in general by intermediary nodes
Roles and Targeting
• Header blocks are targeted to node via "role"
attribute (URI)
• Role is either address of a node or role name
• E.g. this security intermediary (address)
• E.g. any security intermediary (role name)
• Example
<ns:myHeaderBlock role="…/logging" />
• The Body is always targeted to ultimate receiver
Roles and Targeting
• SOAP defines three special roles:
• none
• next
• ultimateReceiver
• The "mustUnderstand" attribute
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If set to “true”, the node must know how to process
the header
If a node doesn't understand a mandatory header
block, it must generate a SOAP fault
Example: Headers with Roles
<?xml version='1.0' ?>
<env:Envelope
xmlns:env="http://www.w3.org/2003/05/soap-envelope">
<env:Header>
<m:reservation xmlns:m="…"
env:role=
"http://www.w3.org/2003/05/soap-envelope/role/next"
env:mustUnderstand="true">
<m:reference>uuid:093a2da1-q345-739r-ba5d-pqff98fe8j7d
</m:reference>
<m:dateAndTime>2001-11-29T13:20:00.000-05:00</m:dateAndTime>
</m:reservation>
<n:passenger xmlns:n=“…"
env:role="
http://www.w3.org/2003/05/soap-envelope/role/next"
env:mustUnderstand="true">
<n:name>Åke Jógvan Øyvind</n:name>
</n:passenger>
</env:Header>
Intermediary Node Algorithm
• Receive message
• Determine roles played
• Verify all mandatory blocks targeted to node are
understood
• Process appropriate header blocks
• Processing possibly produces a fault
• Remove processed headers
• Add new headers if necessary
• Forward message to next node
Ultimate Receiver Algorithm
• Receive message
• Process appropriate header blocks
• Processing possibly produces a fault
• Process all body blocks
• Processing possibly produces a fault
SOAP Messaging Modes
• SOAP supports four modes of messaging
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RPC/Literal
Document/Literal
RPC/Encoded
Document/Encoded
• However, RPC/Encoded and Document/Encoded
modes are explicitly prohibited
Document/Literal Mode
• In the Document/Literal mode of messaging, a
SOAP Body element contains an XML document
fragment
• A well-formed XML element that contains
arbitrary application data (text and other
elements) that belongs to some XML schema and
namespace
Example: Document/Literal Body
<soap:Body>
<po:purchaseOrder orderDate="2003-09-22"
xmlns:po=“http://www.Monson-Haefel.com/jwsbook/PO">
<po:accountName>Amazon.com</po:accountName>
<po:accountNumber>923</po:accountNumber>
...
<po:book>
<po:title>J2EE Web Services</po:title>
<po:quantity>300</po:quantity>
<po:wholesale-price>24.99</po:wholesale-price>
</po:book>
</po:purchaseOrder>
</soap:Body>
RPC/Literal Mode
• The RPC/Literal mode of messaging enables
SOAP messages to model calls to procedures or
method calls with parameters and return values
• The contents of the Body are always formatted as
a struct
• In many cases is used to expose traditional
components (servlet, EJB, RMI) as Web services
Example: RPC/Literal
public interface BookQuote extends java.rmi.Remote {
public float getBookPrice(String ISBN)
throws RemoteException, InvalidISBNException;
}
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:mh="http://www.Monson-Haefel.com/jwsbook/BookQuote">
<soap:Body>
<mh:getBookPrice><isbn>0321146182</isbn></mh:getBookPrice>
</soap:Body>
</soap:Envelope>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:mh="http://www.Monson-Haefel.com/jwsbook/BookQuote" >
<soap:Body>
<mh:getBookPriceResponse><result>24.99</result>
</mh:getBookPriceResponse>
</soap:Body>
</soap:Envelope>
SOAP Faults
• SOAP fault messages are the mechanism by
which SOAP applications report errors to nodes
earlier in the message path
• SOAP faults are returned to the receiver's
immediate sender only
• Fault element information items
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faultcode
• Client, Server, VersionMismatch, MustUnderstand
faultstring
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faultactor
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detail
Example: SOAP Fault
<soap:Fault>
<faultcode>soap:Client</faultcode>
<faultstring>
The ISBN value contains invalid characters
</faultstring>
<faultactor>http://www.xyzcorp.com</faultactor>
<detail>
<mh:InvalidIsbnFaultDetail>
<offending-value>19318224-D</offending-value>
<conformance-rules>
The first nine characters must be digits. The last
character may be a digit or the letter 'X'. Case is
not important.
</conformance-rules>
</mh:InvalidIsbnFaultDetail>
</detail>
</soap:Fault>
SOAP over HTTP
• SOAP messages sent over HTTP are placed in the
payload of an HTTP request or response
POST /jwsbook/BookQuote HTTP/1.1
Host: www.Monson-Haefel.com
Content-Type: text/xml; charset="utf-8"
Content-Length: 295
SOAPAction=""
<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:mh="http://www.Monson-Haefel.com/jwsbook/BookQuote">
<soap:Body>
<mh:getBookPrice>
<isbn>0321146182</isbn>
</mh:getBookPrice>
</soap:Body>
</soap:Envelope>
References
• SOAP Tutorial (W3C Schools)
http://www.w3schools.com/soap/default.asp
• SOAP-1.2 Primer
http://www.w3.org/TR/soap12-part0/
•
SOAP Version 1.2 W3C Specification
http://www.w3.org/TR/soap12-part1/
• Book “J2EE Web Services”
by Richard Monson-Haefel
http://www.amazon.ca/J2EE-Web-ServicesRichard-Monson-Haefel/dp/0321146182

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