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Introduction to Web Services
Bina Ramamurthy This work is partially supported by NSF-DUE-CCLI-A&I Grant 6/10/2018
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Topics for Discussion Webservices and Service Oriented Architectures (SOA) XML (eXtensible Markup Language) SOAP (Simple Object Access Protocol) WS (Web Services) Summary 6/10/2018
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Web Services and SOA Web Services is a technology that allows for applications to communicate with each other in a standard format. A Web Service exposes an interface that can be accessed through XML messaging. A Web service uses XML based protocol to describe an operation or the data exchange with another web service. Ex: SOAP A group of web services collaborating accomplish the tasks of an application. The architecture of such an application is called Service-Oriented Architecture (SOA). 6/10/2018
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SOA in Real World: Report in InfoWorld, May 2, 2005 Issue 18
State of Massachusetts uses SOA to deliver healthcare services. With HTML web application it had no control of look and feel and handling many hospitals. With SOAP based messaging they can easily handle different systems, billing systems, medical records systems etc. Use Microsoft-based systems. Countrywide financial simplifies lending: IBM Websphere based SOA is used to deliver services. Guardian Life Insurance uses SOA: IBM websphere based services. Uses EJB for business logic. British Telecom uses combination of BEA systems and Microsoft’s Connected Services Framework. Billing backend and operational support for the organization are web services. Legacy systems are enabled as web services. Amazon.com provides WS API for developers to implement applications leveraging their architecture and data. 6/10/2018
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XML XML is a markup language, developed by W3C (World Wide Web Consortium), mainly to overcome the limitations of HTML. But it took a life of its own and has become a very popular part of distributed systems. We will examine its definition, associated specifications (DTD, XSLT etc.), Java APIs available to process XML, protocols and services based on XML, and the role XML plays in a distributed computing environment. 6/10/2018
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First Look at XML It has no predefined tags. It is stricter.
Such as in HTML Domains may specify their own set of standard tags It is stricter. Most html document have errors and the browser have to built to take care of these. On the other hand XML has a strict syntax. There is a notion of validity and A notion of well-formed. 6/10/2018
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An Example: Memo See the two documents enclosed: one in html and the other in XML formats. Observe the meaningful tags in XML. Compare it to a class definition: it looks like a class with data definitions and accessors (tags). 6/10/2018
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Memo.html vs memo.xml <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="content-type" content="text/html; charset=ISO "> <title>memo.html</title> </head> <body> <h3>Hello World</h3> Bina<br> CSE486 DS Students <br> Wake up everyone<br> BR<br> <br> </body> </html> <?xml version="1.0" ?> <!DOCTYPE memo (View Source for full doctype...)> - <memo> <header>Hello World</header> <from>bina</from> <to>CSE486 DS Students</to> <body>Wake up everyone</body> <sign>br</sign> </memo> 6/10/2018
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XML to SOAP Simple xml can facilitate sending message to receive information. The message could be operations to be performed on objects. Simple Object Access Protocol (SOAP) 6/10/2018
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SOAP Request <soap:Envelope xmlns:soap=" <soap:Body> <getProductDetails xmlns=" <productId>827635</productId> </getProductDetails> </soap:Body> </soap:Envelope> 6/10/2018
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SOAP Reply <soap:Envelope xmlns:soap=" <soap:Body> <getProductDetailsResponse xmlns=" <getProductDetailsResult> <productName>Toptimate 3-Piece Set</productName> <productId>827635</productId> <description>3-Piece luggage set. Black Polyester.</description> <price>96.50</price> <inStock>true</inStock> </getProductDetailsResult> </getProductDetailsResponse> </soap:Body> </soap:Envelope> 6/10/2018
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SOAPWeb Services (WS)SOA
Read this paper: 6/10/2018
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WS Stack Service Flow WSFL Service Discovery UDDI Quality of Service
Security Management Quality of Service Service Discovery UDDI Service Publication UDDI Service Description WSDL XML-based Messaging SOAP HTTP, FTP, MQ , IIOP Network 6/10/2018
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WS Interoperability Infrastructure
Service Description WSDL XML Messaging SOAP Network HTTP Do you see any platform or language dependencies here? 6/10/2018
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Service Oriented Architectures
Lets look at some success stories. Amazon.com has is data collection available web services developers. See these URLs: Amazon.com E-Commerce Service (ECS) A cool application 6/10/2018
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Summary We looked at foundational concepts supporting web services: XML, SOAP, WSDL and Web Services standards. We also illustrated the concepts using sample programs. We will discuss REST-based web services and WDSL in the next lectures. 6/10/2018
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