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Web Service Definition Language

Web Service Definition Language. Web Service Definition Language ( WSDL ). What is a web service? [ F. Leymann 2003 ] A piece of code that can communicate with other pieces of code via the Internet

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Web Service Definition Language

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  1. Web Service Definition Language

  2. Web Service Definition Language (WSDL) • What is a web service? [F. Leymann 2003] • A piece of code that can communicate with other pieces of code via the Internet • Can hide “middleware ideosynchracies” (underlying component model, invocation protocol etc.) as far as possible • WSDL defines • What the service is – interface • Access specification – how • Location of the service – where Web Services: WSDL

  3. Ingredients of WSDL Interface Supports Port Type Operation How to invoke Formats & Protocols Input & Output Binding Message How to encode Accessspecification Implements Provides Port Service Endpoints Web Services: WSDL

  4. Web Services Definition Language (WSDL) • Traditional I/O signatures • Peer-to-peer: web service can act as client or server • Proactive : send request send request, block till response • Reactive : receive request receive request, send response bill_payment out: bill in: payment order bill order Supplier’ Supplier receipt payment receipt • Port: mechanism to cluster operations • Port as unit of interoperation between services Web Services: WSDL

  5. Main Structure of WSDL <definitions namespace = “http://… ”> <types> XML schema types </type> <message> definition of a message </message> <portType> a set of operations </portType> <binding> communication protocols </binding> <service> a list of binding and ports </service> </definitions> Web Services: WSDL

  6. Types • <types> define data types used in defining messages • XML Schema, DTD, and etc. • XML Schema must be supported by any vendor of WSDL conformant products Web Services: WSDL

  7. Type Examples <types> <schema targetNamespace=“http://example.com/stockquote.xsd” xmlns=“http://www.w3.org/2000/10/XMLSchema”> <element name=“TradePriceRequest”> <complexType> <all> <element name=“tickerSymbol” type=“string“ minOccur = “1” maxOccur=“10”/> <element name = “payment”> <complexType> <choice> <element name = “account” type=“string” /> <element name = “creditcard” type=“string” /> </choice> </complexType> </element> </all> </complexType> </element> </schema> </types> Web Services: WSDL

  8. WSDL Messages • A <message> element defines the data elements of an operation • Each message can be the input or output of an operation, and may consist of one or more parts • A part resembles a parameter of a function Web Services: WSDL

  9. Message Examples <message name=“GetLastTradePriceInput”> <part name=“body” element="TradePriceRequest"/> </message> <message name=“GetLastTradePriceOutput”> <part name=“body” element=“TradePrice” /> </message> Web Services: WSDL

  10. WSDL Ports • The <portType> element is the most important WSDL element: it defines • a web service • the operations that can be performed, and • the messages that are involved • The <port> defines the connection point to a web service, an instance of <portType> • It can be compared to a function library (or a module, or a class) in a traditional programming language • Each operation can be compared to a function in a traditional programming language Web Services: WSDL

  11. <portType name=“StockQuotePortType”> <operation name=“GetLastTradePrice”> <input message=“tns:GetLastTradePriceInput” /> <output message=“tns:GetLastTradePriceOutput” /> </operation> </portType> Web Services: WSDL

  12. Operation Types • The request-response type is the most common operation type, but WSDL defines four types: • One-way: The operation can receive a message but will not return a response • Request-response: The operation can receive a request and will return a response • Solicit-response: The operation can send a request and will wait for a response • Notification: The operation can send a message but will not wait for a response • WSDL 1.2 adds: request – multiple response Web Services: WSDL

  13. One-Way Operation <message name=“newTermValues”> <part name=“term” type=“xs:string” /> <part name=“value” type=“xs:string” /> </message> <portType name=“glossaryTerms”> <operation name=“setTerm”> <input name=“newTerm” message=“newTermValues” /> </operation> </portType > Web Services: WSDL

  14. Request-Response Operation <message name="getTermRequest"> <part name="term" type="xs:string"/></message> <message name="getTermResponse"> <part name="value" type="xs:string"/> </message> <portType name="glossaryTerms"> <operation name="getTerm"> <input message="getTermRequest"/> <output message="getTermResponse"/> </operation></portType> Web Services: WSDL

  15. One-way and Notification Example <portType name=“RegisterPort"> <operation name=“register"> <input name=“customerInfo“ message=“RegInfo"/> </operation> <operation name = “register Response”> <output name = “response” message=“ResponseInfo”/> </operation> </portType > Web Services: WSDL

  16. Binding • Binding defines how message are transmitted, and the location of the service • <binding> element has two attributes: • type: the port type • name: name of the binding • <soap:binding> has two attributes: • style: either “document” or “rpc” • transport: protocol to use, e.g., “http” Web Services: WSDL

  17. Binding Example <binding name="StockQuoteSoapBinding“ type="tns:StockQuotePortType"> <soap:binding style=“document” transport=“http://schemas.xmlsoap.org/soap/http” /> <operation name="GetLastTradePrice"> <soap:operation soapAction=“http://example.com/GetLastTradePrice” /> <input> <soap:body use=“literal” /> </input> <output> <soap:body use=“literal” /> </output> </operation> </binding> Web Services: WSDL

  18. <binding name="StockQuoteSoapBinding“ type="tns:StockQuotePortType"> <soap:binding style="document“ transport="http://schemas.xmlsoap.org/soap/http"/> <operation name="GetLastTradePrice"> <input> <soap:body use=“encoded” encodingStyle=“http://schemas.xmlsoap.org/ soap/encoding/” /> </input> <output> … </output> </operation> </binding> Web Services: WSDL

  19. Services <service name=“StockQuoteService”> <documentation> My first service </documentation> <port name=“StockQuotePort” binding=“tns:StockQuoteBinding”> <soap:address location=“http://example.com/stockquote” /> </port> </service> Web Services: WSDL

  20. Summary • WSDL provides a practical framework for defining • Services: functions and input/output • Bindings using SOAP (document style or PRC style) • Service entry points • Many WSDL services exist (www.xmethods.com), e.g., • http://soap.achchex.com/exec/btrnsoap.dll/wsdl/IBTRNSOAP Web Services: WSDL

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