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HTML Form to Web Service Gateway

Learn about calling web services through WSDL and SOAP, creating self-describing applications, and managing web service invocations. Understand the two main layers - Description and Invocation - and explore examples of SOAP messaging. Discover how to convert page forms to WSDL descriptions and handle SOAP requests effectively.

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HTML Form to Web Service Gateway

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  1. HTML Form to Web Service Gateway Ross Shannon Supervisor: Dr. Nick Kushmerick Moderator: Dr. Mel Ó Cinnéide

  2. Web Services • Modular, self-describing applications deployed and invoked from anywhere on the Web • Can be thought of as calling a function across the Internet • Most programming languages have a way of requesting web services • A number of companies have created web services, but they’re not as widespread as was hoped • Two main layers: Description and Invocation

  3. WSDL • “Web Services Description Language” • Programmer’s manual on how to call a web service • Defines • Methods available from a service • Names and types of each argument

  4. WSDL Example <message name="compoundInterestInput"> <part name="amount" type="float"/> <part name="rate" type="float"/> <part name="years" type="int"/> </message> <message name="compoundInterestOutput"> <part name="ComputedInterest" type="float"/> </message> <portType name="compoundInterestPort"> <operation name="computeCompoundInterest"> <input message="compoundInterestInput"/> <output message=" compoundInterestOutput"/> </operation> </portType>

  5. SOAP • “Simple Object Access Protocol” • Uses existing standards like XML, HTTP etc. • Client wraps the request in a “SOAP Envelope” for transport • Once the service has responded to the request, it wraps the response in SOAP and passes it back

  6. SOAP Example • A simple SOAP message to call a procedure that requires a single parameter: <SOAP-ENV:Envelope> <SOAP-ENV:Body>    <m:GetLastTradePrice xmlns:m="http://example.com/StockTrading">       <symbol>YHOO</symbol>     </m:GetLastTradePrice>   </SOAP-ENV:Body> </SOAP-ENV:Envelope>

  7. SOAP Example (2) • The SOAP response to the preceding request: <SOAP-ENV:Envelope> <SOAP-ENV:Body>    <m:GetLastTradePriceResult xmlns:m="http://example.com/StockTrading"> <tradeprice>31.2</tradeprice>     </m:GetLastTradePriceResult>   </SOAP-ENV:Body> </SOAP-ENV:Envelope>

  8. Project Dichotomy… The project needs two parts: • Convert all forms on a page into an equivalent WSDL description

  9. Project Dichotomy… (2) And a second part: • Allow invocations of the “service” by responding to SOAP requests and converting these back into normal form submits

  10. Future Work • Make better guesses at WSDL types • Clean up HTML output • Cross-validate SOAP request with WSDL file

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