simple object access protocol. web services: soap2 why simple object access protocol light weight...

Simple Object Access Protocol

Web Services: SOAP 2

Why Simple Object Access Protocol

Light weight replacement for complicated distributed object technology

Originally for BizTalk (Microsoft/UserLand/Developmentor)

Now a W3C standard

Based on XML and HTTP


Port vs Web Server

ExternalApplication

ExternalApplication

ExternalApplication

TC

P

InternalService

InternalService

InternalService


Port vs Web Server

ExternalApplication

ExternalApplication

ExternalApplication

TC

P

InternalService

InternalService

InternalService

WebServer

XML

paylo

ad “XML-RPC”

Port 80? SOAP is not restricted to port 80


POST /Temperature HTTP/1.1Host: www.weather.comContent-Type: text/xmlContent-Length: <whatever>SOAPAction: “urn:StockQuote#GetQuote”

<s:Envelope xmlns:s=“http://www.w3.org/2001/06/soap-envelope"><s:Body>

… …</s:Body>

</s:Envelope>

HTTP Header

XML Payload(SOAP request)

Soap Extensions

SOAP over HTTP

Request example


HTTP/1.1 200 OKContent-Type: text/xmlContent-Length: <whatever>

<s:Envelope xmlns:s=“http://www.w3.org/2001/06/soap-envelope"><s:Body>

… …</s:Body>

</s:Envelope>

SOAP over HTTP

Response exampleHTTP Header

XML Payload(SOAP response)


SOAP Example: Request

<soap:Envelope> <soap:Body> <xmlns:m= "http://www.amzn.org/books" /> <m:GetBookPrice> <m:BookName>Fast Food

Nation</m:BookName> </m:GetBookPrice> </soap:Body> </soap:Envelope>


SOAP Example: Response

<soap:Envelope> <soap:Body> <xmlns:m="http://www.amzn.org/books" /> <m:GetBookPriceResponse> <m:Price>34.5</m:Price> </m:GetBookPriceResponse> </soap:Body> </soap:Envelope>


SOAP Example: Error

<soap:Fault> <faultcode>0x800700E</faultcode> <faulstring>Unknown book</faultstring></soap:Fault>


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”


SOAP Message with Binary Attachments

A SOAP message can also contain binary attachments using MIME encoding

SOAP EnvelopeSOAP Header

(optional)

SOAP Body“payload”

MIME HeaderRoot Body PartMIME Boundary

Body PartMIME Boundary

Attachment


SOAP Structure

Envelope containsHeaderBody

Header is optionalOut-of-band information

such as…Authentication information

Message routesLoggingTransaction flow

Body contains XML body of RPC call

SOAP Envelope

SOAP Header

Header Block

Header Block

. . .

SOAP Body

Body Block

Body Block

. . .


SOAP Example

<?xml version="1.0" encoding="UTF-8" ?><env:Envelope

xmlns:env="http://www.w3.org/2001/09/soap-envelope"> <env:Header> <n:alertcontrol xmlns:n="http://example.org/alertcontrol"> <n:priority>1</n:priority> <n:expires>2001-06-22T14:00:00-05:00</n:expires> </n:alertcontrol> </env:Header> <env:Body> <m:alert xmlns:m="http://example.org/alert"> <m:msg>Pick up Mary at school at 2pm</m:msg> </m:alert> </env:Body> </env:Envelope>


XML Messaging in SOAP

EDI: Electronic Document InterchangeSOAP with EDI: XML documents

“Document style SOAP”

RPC: distributed computing, web services“RPC-style” SOAP: parameters and return

values


<s:Envelope xmlns:s=“http://www.w3.org/2001/06/soap-envelope”><s:Header>

<m:transaction xmlns:m=“soap-transaction” s:mustUnderstand=“true”>

<transactionID>1234</transactionID></transaction>

</s:Header><s:Body>

<n:purchaseOrder xmlns:n=“urn:OrderService”><from><person>Christopher Robin</person>

<dept>Accounting</dept></from><to><person>Pooh Bear</person>

<dept>Honey></dept></to><order><quantity>1</quantity> <item>Pooh Stick</item></order>

</n:purchaseOrder></s:Body>

</s:Envelope>

Purchase Order in Document-Style SOAP


RPC Messages

Typically two messages

SOAP Client SOAP Server

Request Message

Response Message


An RPC-style SOAP Message

public Float getQuote (String symbol);

<s:Envelope xmlns:s=“http://www.w3.org/2001/06/soap-envelope”><s:Header>

<m:transaction xmlns:m=“soap-transaction”s:mustUnderstand=“true”>

<transactionID>1234</transactionID></m:transaction>

</s:Header><s:Body>

<n:getQuote xmlns:n=“urn:QuoteService”><symbol xsi:type=“xsd:string”>

IBM</symbol>

</n:getQuote></s:Body>

</s:Envelope>


SOAP Response

<s:Envelope xmlns:s=http://www.w3.org/2001/06/soap-envelope><s:Body>

<n:getQuoteResponse xmnls:n=“urn:QuoteService”><value xsi:type=“xsd:float”>

98.06</value>

</n:getQuoteResponse></s:Body>

</s:Envelope>

SOAP Faults

<s:Envelope xmlns:s=“http://www.w3.org/2001/06/soap-envelope” ><s:Body>

<s:Fault><faultcode>Client.Authentication</faultcode><faultstring>Invalid credentials</faultstring><faultactor>http://acme.com/</faultactor><details> <!-- application specific details></details>

</s:Fault></s:Body>

</s:Envelope>


Standard SOAP Fault Codes

Version Mismatch MustUnderstand: specify which header blocks

were not understood Server: error can’t be directly linked to the

processing of the message Client: there is a problem in the message (e.g.

invalid authentication credentials)


SOAP Data Encoding One possible method of serializing data and

encode them into XML Section 5 of the SOAP standard General rules


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)

<name><firstname>Joe</firstname><lastname>Smith</lastname>

</name>


Arrays

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

<people><person name=‘joe smith’ /><person name=‘john doe’ />

</people>


Multi-Referenced Accessor

<people><person name=‘joe smith’>

<address href=‘#address-1’></person><person name=‘john doe’>

<address href=‘#address-1’></person>

</people><address id=‘address-1’>

<street>111 First Street</street><city>New York</city><state>New York</state>

</address>


Express the Data Type of an Accessor Use the xsi:type attribute on each accessor,

explicitly referencing the data type according to the XML Schema specification:<person><name xsi:type=“xsd:string”>John Doe</name>

Reference an XML Schema document that defines the exact data type of a particular element within its definition:

<person xmlns=“personschema.xsd”><name>John Doe</name></person>

Reference some other type of schema document that defines the data type of a particular element within its definition:<person xmlns=“urn:some_namespace”><name>John Doe</name>


SOAP Data Types Two alternate syntaxes for expressing instances

of data types Anonymous accessor:

<SOAP-ENC:int>36</SOAP-ENC:int> Anonymous because its name is its type rather

than a meaningful id for the value Named accessor:

<value xsi:type=“xsd:int”>36</value>


Arrays

Arrays

int a[3] = {1, 2, 3};

b = Add([in]a);

<m:Add xmlns:m=“http://a.com/Calculator” xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/”> <a SOAP-ENC:arrayType=“xsd:int[3]”> <SOAP-ENC:int>1</SOAP-ENC:int> <SOAP-ENC:int>2</SOAP-ENC:int> <SOAP-ENC:int>3</SOAP-ENC:int> </a></m:Add>


By value : Add([in] int a, [in] int b);

By reference : Square([in, out] int &a);

Values and References

<m:Add xmlns:m=“http://a.com/Calculator”><a xsi:type=“integer”>3</a><b xsi:type=“integer”>4</b>

</m:Add>

<m:Add xmlns:m=“http://a.com/Calculator”><a href=“#arg” />

</m:Add><a id=“arg” xsi:type=“integer”>8</a>


Summary

SOAP protocol: an XML encoding scheme to exchange information between web processes:Document style: XML documentsRPC style: packing parameters in XML format

Typically SOAP/HTTP, others are possible Low level in terms of process/service modeling

simple object access protocol. web services: soap2 why simple object access protocol light weight...

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