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Enterprise Computing: Web Services

Enterprise Computing: Web Services. Exercise. What is wrong with JEE? Why would you not use it for web-based application integration? Why would you not use it for intranet-based application integration?. Web Services: Definitions.

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Enterprise Computing: Web Services

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  1. Enterprise Computing:Web Services

  2. Exercise • What is wrong with JEE? • Why would you not use it for web-based application integration? • Why would you not use it for intranet-based application integration?

  3. Web Services: Definitions • A Web service is a collection of functions that are packaged as a single entity and published to the network for use by other programs. • Web services are building blocks for creating open distributed systems, and allow companies and individuals to quickly and cheaply make their digital assets available worldwide. • Web Service standards form a platform-independent, open framework for describing services, discovering businesses, and integrating business services.

  4. eXtensible Markup Language • A common data format derived from SGML • Language independent, hierarchical and self-describing • Uses tag-based structure similar to HTML to define XML documents <?xml version="1.0" encoding="ISO-8859-1" ?> <bankaccount type=“Current”> <name>John Smith</name> <address> <line 1>1 Grafton Street </line1> <line 2>Dublin 2, Ireland </line2> </address> </bankaccount> • Supports arbitrarily complex data formats • Schema (defined in xsd files) can be used to define document formats • Fragment defining a BankAccount as a type of financial record <xsd:element name="purchaseOrder" type="PurchaseOrderType"/>

  5. eXtensible Markup Language • Independent of IT infrastructure • Separates the what from the how • Many industry based schema standards have been developed • For example, Financial Services: • ISO15022 (SWIFT, FIX, FpML) • XBRL (business reporting) • Any XML based infrastructure can handle multiple and evolving schema standards without excessive cost • Due to changes in business relationships • Due to regulatory changes (e.g. Basil II) • Due to evolution of the schemas themselves

  6. The Web Services architecture UDDI Registry • Web Services is based on three standards • Simple Object Access Protocol (SOAP) • defines the communication mechanism • Universal Directory Discovery Interface (UDDI) • defines the registry of interface definitions • Web Service Definition Language • defines the actual interfaces 2. Request contract information 3. Retrieve WSDL definition WSDL Service Consumer WSDL 4. Exchange SOAP messages Service Provider 1. Register contract information

  7. SOAP- Simple Object Access Protocol SOAP1.1 Message Structure • XML based protocol for exchange of information • Encoding rules for datatype instances • Convention for representing RPC invocations • Used with XML Schema • Normally HTTP-based • Uses Request/Response • Two different modes • RPC • Document • SOAP with Attachments allow arbitrary data to be packaged. SOAP Envelope Header Entries Header Body Fault Element

  8. SOAP Example: Request • Sample SOAP Message embedded in an HTTP Request POST /StockQuote HTTP/1.1 Host: www.stockquoteserver.com Content-Type: text/xml; charset="utf-8" Content-Length: 1024 SOAPAction: "http://example.org/2001/06/quotes" <env:Envelope xmlns:env="http://www.w3.org/2001/06/soap-envelope" > <env:Body> <m:GetLastTradePrice env:encodingStyle="http://www.w3.org/2001/06/soap-encoding" xmlns:m="http://example.org/2001/06/quotes"> <symbol>IBM</symbol> </m:GetLastTradePrice> </env:Body> </env:Envelope>

  9. SOAP Example: Response • SOAP message sent by the StockQuote service in the corresponding HTTP response to the request HTTP/1.1 200 OK Content-Type: text/xml; charset="utf-8" Content-Length: 512 <env:Envelope xmlns:env="http://www.w3.org/2001/06/soap-envelope" > <env:Body> <m:GetLastTradePriceResponse env:encodingStyle="http://www.w3.org/2001/06/soap-encoding" xmlns:m="http://example.org/2001/06/quotes"> <Price>97.5</Price> </m:GetLastTradePriceResponse> </env:Body> </env:Envelope>

  10. UDDI • Universal Description, Discovery and Integration • Platform-independent, open framework for describing services, discovering businesses, and integrating business services. • A DNS-like model implementation of the directory • Originally intended to support global registries • Created during the .com bubble. • Includes White, Green and Yellow Pages for search purposes • Now primarily inside organisations if at all

  11. Web Service Description Language (WSDL) • Interface definition language in XML • Conceptually, no different from Enterprise Java Bean or Common Gateway Interface • Based on XML Schema • Can appear to be very verbose • An interface description is a contract between the server developers and the client developers • WSDL describes the web service • Similar to Java method signatures

  12. Interoperability Challenges • Interoperability remains the chief challenge of web services • Complex and imprecise standard • Tools generating SOAP, WSDL, UDDI, etc. need to be interoperable • Web Services Interoperability (WS-I) focus on creating to Interoperability • WS-I Basic Profile 1.0 defines an interoperable web services platform

  13. WS-I Basic Profile • WS-I Basic Profile 1.1: • SOAP 1.1 • WSDL 1.1 • Must use HTTP binding, should use HTTP 1.1 • XML Schema Part 1, Part 2 • May use HTTPS • SOAP messages should use document/literal • V1.2 in draft form

  14. Web Services: Another approach to distributed computing • Builds on the legacy of CORBA, J2EE etc • It is not a new component model, programming model or programming language. • UDDI/WSDL/SOAP provide another distributed computing technology • Standards developing for the Quality of Services and other EAI-type functionality. • Exercise: Write down the standards for J2EE Quality Of Service Discovery Description Messaging Transport

  15. Web Services: Another approach to distributed computing WS- ReliableMessaging WS- Security WS-BA Quality Of Service WS-Coordination UDDI Discovery XSD, WSDL, WS-Policy Description SOAP Messaging XML HTTP, MQ, SMTP Transport

  16. Web Services Strengths • Interoperability • Based on open standards, utilizes existing infrastructure • Can be accessed from any programming language/model • Ubiquity • Communicates through XML/HTTP – Any system that supports these standards, supports Web Services • Support from all major software vendors (IBM and Microsoft) • Low barrier to entry • Concepts easy to understand, easy to implement • Toolkits allow COM, JEE, and CORBA components to be exposed as Web Services

  17. Web Services and XML/WS standards • Java API for XML Parsing (JAXP) • JAXP enables applications to parse and transform XML documents • Independent of XML processor implementation • JAXP includes common industry standard components/interfaces • DOM (Document Object Model and SAX (Simple API for XML Processing) • XSLT (XML Style Language Transformations) • JAXP adds additional functionality beyond these standards • Java API for XML • Remote Procedure Call (JAX-RPC) • SOAP (Simple Object Access Protocol) 1.1 specification • Java API for XML Registries (JAX-R) • APIs to access UDDI Registry

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