Simple Object Access Protocol

1
Simple Object Access Protocol
2
Why Simple Object Access Protocol

• Light weight replacement for complicated
  distributed object technology
• Originally for BizTalk (Microsoft/UserLand/Develop
  mentor)
• Now a W3C standard
• Based on XML and HTTP

3
Port vs Web Server
External Application
Internal Service
External Application
Internal Service
TCP
External Application
Internal Service
4
Port vs Web Server
External Application
Internal Service
Web Server
External Application
Internal Service
XML payload
TCP
External Application
Internal Service

• XML-RPC
• Port 80?
• SOAP is not restricted to port 80

5
SOAP over HTTP

• Request example

POST /Temperature HTTP/1.1 Host
www.weather.com Content-Type text/xml Content-Len
gth ltwhatevergt SOAPAction urnStockQuoteGetQuo
te ltsEnvelope xmlnsshttp//www.w3.org/2001/
06/soap-envelope"gt ltsBodygt
lt/sBodygt lt/sEnvelopegt
HTTP Header
Soap Extensions
XML Payload (SOAP request)
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SOAP over HTTP

• Response example

HTTP Header

• HTTP/1.1 200 OK
• Content-Type text/xml
• Content-Length ltwhatevergt
• ltsEnvelope xmlnsshttp//www.w3.org/2001/06/soa
  p-envelope"gt
• ltsBodygt
• lt/sBodygt
• lt/sEnvelopegt

XML Payload (SOAP response)
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SOAP Example Request

• ltsoapEnvelopegt
• ltsoapBodygt
• ltxmlnsm "http//www.amzn.org/books" /gt   
  
• ltmGetBookPricegt
• ltmBookNamegtFast Food
• Nationlt/mBookNamegt  
•     lt/mGetBookPricegt
• lt/soapBodygt
• lt/soapEnvelopegt

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SOAP Example Response

• ltsoapEnvelopegt
• ltsoapBodygt
• ltxmlnsm"http//www.amzn.org/books" /gt
• ltmGetBookPriceResponsegt
• ltmPricegt34.5lt/mPricegt
• lt/mGetBookPriceResponsegt
• lt/soapBodygt
• lt/soapEnvelopegt

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SOAP Example Error

• ltsoapFaultgt
• ltfaultcodegt0x800700Elt/faultcodegt
• ltfaulstringgtUnknown booklt/faultstringgt
• lt/soapFaultgt

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SOAP Message

• A SOAP message is contained within an XML
  envelope, complete with a Header and Body

SOAP Envelope
SOAP Header (optional)
SOAP Body payload
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SOAP Message with Binary Attachments

• A SOAP message can also contain binary
  attachments using MIME encoding

MIME Header
MIME Boundary
Root Body Part
SOAP Envelope
SOAP Header (optional)
SOAP Body payload
MIME Boundary
Body Part
Attachment
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SOAP Structure

• Envelope contains
• Header
• Body
• Header is optional
• Out-of-band information such as
• Authentication information
• Message routes
• Logging
• Transaction flow
• Body contains XML body of RPC call

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SOAP Example

• lt?xml version"1.0" encoding"UTF-8" ?gt
• ltenvEnvelopexmlnsenv"http//www.w3.org/2001/09
  /soap-envelope"gt
• ltenvHeadergt
• ltnalertcontrol
• xmlnsn"http//example.org/alertcontro
  l"gt
• ltnprioritygt1lt/nprioritygt
• ltnexpiresgt2001-06-22T140000-0500lt/nexp
  iresgt
• lt/nalertcontrolgt
• lt/envHeadergt
• ltenvBodygt
• ltmalert xmlnsm"http//example.org/alert"gt
  
• ltmmsggtPick up Mary at school at
  2pmlt/mmsggt
• lt/malertgt
• lt/envBodygt
• lt/envEnvelopegt

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XML Messaging in SOAP

• EDI Electronic Document Interchange
• SOAP with EDI XML documentsDocument style
  SOAP
• RPC distributed computing, web services
• RPC-style SOAP parameters and return values

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Purchase Order in Document-Style SOAP
ltsEnvelope xmlnsshttp//www.w3.org/2001/06/soa
p-envelopegt ltsHeadergt ltmtransaction
xmlnsmsoap-transaction smustUnderstand
truegt lttransactionIDgt1234lt/transactionIDgt lt
/transactiongt lt/sHeadergt ltsBodygt ltnpurchase
Order xmlnsnurnOrderServicegt ltfromgtltperson
gtChristopher Robinlt/persongt ltdeptgtAccountinglt
/deptgt lt/fromgt lttogtltpersongtPooh
Bearlt/persongt ltdeptgtHoneygtlt/deptgt lt/togt
ltordergtltquantitygt1lt/quantitygt ltitemgtPooh
Sticklt/itemgt lt/ordergt lt/npurchaseOrdergt lt/s
Bodygt lt/sEnvelopegt
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RPC Messages

• Typically two messages

Request Message
SOAP Client
SOAP Server
Response Message
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An RPC-style SOAP Message
public Float getQuote (String symbol) ltsEnvelop
e xmlnsshttp//www.w3.org/2001/06/soap-envelope
gt ltsHeadergt ltmtransaction
xmlnsmsoap-transaction smustUndersta
ndtruegt lttransactionIDgt1234lt/transactionIDgt
lt/mtransactiongt lt/sHeadergt ltsBodygt ltnget
Quote xmlnsnurnQuoteServicegt ltsymbol
xsitypexsdstringgt IBM lt/symbolgt lt/n
getQuotegt lt/sBodygt lt/sEnvelopegt
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SOAP Response
ltsEnvelope xmlnsshttp//www.w3.org/2001/06/soap
-envelopegt ltsBodygt ltngetQuoteResponse
xmnlsnurnQuoteServicegt ltvalue
xsitypexsdfloatgt 98.06 lt/valuegt lt/n
getQuoteResponsegt lt/sBodygt lt/sEnvelopegt
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SOAP Faults
ltsEnvelope xmlnsshttp//www.w3.org/2001/06/soa
p-envelope gt ltsBodygt ltsFaultgt ltfaultcodegt
Client.Authenticationlt/faultcodegt ltfaultstringgt
Invalid credentialslt/faultstringgt ltfaultactorgth
ttp//acme.com/lt/faultactorgt ltdetailsgt lt!--
application specific detailsgtlt/detailsgt lt/sFaul
tgt lt/sBodygt lt/sEnvelopegt
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Standard SOAP Fault Codes

• Version Mismatch
• MustUnderstand specify which header blocks were
  not understood
• Server error cant be directly linked to the
  processing of the message
• Client there is a problem in the message (e.g.
  invalid authentication credentials)

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SOAP Data Encoding

• One possible method of serializing data and
  encode them into XML
• Section 5 of the SOAP standard
• General rules

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Compound Values

• A compound value represents a combination of two
  or more accessors grouped as children of a single
  accessor
• Each accessor has a different name (structs)

ltnamegt ltfirstnamegtJoelt/firstnamegt ltlastnamegtSmit
hlt/lastnamegt lt/namegt
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Arrays

• An array is a compound value in which the
  accessors have the same name

ltpeoplegt ltperson namejoe smith /gt ltperson
namejohn doe /gt lt/peoplegt
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Multi-Referenced Accessor

• ltpeoplegt
• ltperson namejoe smithgt
• ltaddress hrefaddress-1gt
• lt/persongt
• ltperson namejohn doegt
• ltaddress hrefaddress-1gt
• lt/persongt
• lt/peoplegt
• ltaddress idaddress-1gt
• ltstreetgt111 First Streetlt/streetgt
• ltcitygtNew Yorklt/citygt
• ltstategtNew Yorklt/stategt
• lt/addressgt

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Express the Data Type of an Accessor

• Use the xsitype attribute on each accessor,
  explicitly referencing the data type according to
  the XML Schema specification
• ltpersongtltname xsitypexsdstringgtJohn
  Doelt/namegt
• Reference an XML Schema document that defines the
  exact data type of a particular element within
  its definition
• ltperson xmlnspersonschema.xsdgt
• ltnamegtJohn Doelt/namegtlt/persongt
• Reference some other type of schema document that
  defines the data type of a particular element
  within its definition
• ltperson xmlnsurnsome_namespacegt
• ltnamegtJohn Doelt/namegt

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SOAP Data Types

• Two alternate syntaxes for expressing instances
  of data types
• Anonymous accessor
• ltSOAP-ENCintgt36lt/SOAP-ENCintgt
• Anonymous because its name is its type rather
  than a meaningful id for the value
• Named accessor
• ltvalue xsitypexsdintgt36lt/valuegt

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Arrays

• Arrays

int a3 1, 2, 3 b Add(ina)
ltmAdd xmlnsmhttp//a.com/Calculator
xmlnsSOAP-ENC "http//schemas.xmlsoap.org/soap/e
ncoding/gt lta SOAP-ENCarrayTypexsdint3gt
ltSOAP-ENCintgt1lt/SOAP-ENCintgt
ltSOAP-ENCintgt2lt/SOAP-ENCintgt
ltSOAP-ENCintgt3lt/SOAP-ENCintgt lt/agt lt/mAddgt
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Values and References

• By value Add(in int a, in int b)
• By reference Square(in, out int a)

ltmAdd xmlnsmhttp//a.com/Calculatorgt lta
xsitypeintegergt3lt/agt ltb xsitypeintegergt4lt
/bgt lt/mAddgt
ltmAdd xmlnsmhttp//a.com/Calculatorgt lta
hrefarg /gt lt/mAddgt lta idarg
xsitypeintegergt8lt/agt
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Summary

• SOAP protocol an XML encoding scheme to exchange
  information between web processes
• Document style XML documents
• RPC style packing parameters in XML format
• Typically SOAP/HTTP, others are possible
• Low level in terms of process/service modeling