Introduction to Web Services Bina Ramamurthy bina@cse.buffalo.edu This work is partially supported by NSF-DUE-CCLI-A&I Grant 0311473 4/15/2019
Topics for Discussion Webservices and Service Oriented Architectures (SOA) XML (eXtensible Markup Language) SOAP (Simple Object Access Protocol) WS (Web Services) Summary 4/15/2019
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). 4/15/2019
SOA in Real World: Report in InfoWorld, May 2, 2005 Issue 18 http://www.infoworld.com/article/05/05/02/18FEsoabt_1.html?WEB%20SERVICES 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. 4/15/2019
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. 4/15/2019
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. 4/15/2019
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). 4/15/2019
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-8859-1"> <title>memo.html</title> </head> <body> <h3>Hello World</h3> Bina<br> CSE507 SOA and WS 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>CSE507 SOA and WS Students</to> <body>Wake up everyone</body> <sign>br</sign> </memo> 4/15/2019
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) 4/15/2019
SOAP Request <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <getProductDetails xmlns="http://warehouse.example.com/ws"> <productId>827635</productId> </getProductDetails> </soap:Body> </soap:Envelope> 4/15/2019
SOAP Reply <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"> <soap:Body> <getProductDetailsResponse xmlns="http://warehouse.example.com/ws"> <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> 4/15/2019
SOAPWeb Services (WS)SOA Read this paper: http://www.w3.org/DesignIssues/WebServices.html 4/15/2019
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 Email, IIOP Network 4/15/2019
WS Interoperability Infrastructure Service Description WSDL XML Messaging SOAP Network HTTP Do you see any platform or language dependencies here? 4/15/2019
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 4/15/2019
Summary We looked at foundational concepts supporting web services: XML, SOAP, WSDL and Web Services standards. We also illustrated the concepts using sample programs. 4/15/2019