DOT NET WEB SERVICES Agenda  Web Services Discussion  Quick DOT NET DEMO  Assignment Assignment  Lab: Hello World Service/Client  Lab: Google Client  Lab: Open Search Info Source

Importance of Web Services  Larry Page, on why Google introduced its search API: “Within a few years, there will be more programs (agents) accessing Google than people accessing Google.”

Web Services Discussion 1. Define web service 2. What is the “problem” that web services address? 3. What are the emerging standards for web services. Who supports each? What are the advantages of each?

What is a web service?  A remote procedure call (RPC) over HTTP.  A web-accessible operation that takes input and returns results in XML.  Like a web page, but just the data with no presentation specifications.  Web definitions Web definitions

Without Web Services: Content and Presentation mixed Database Servlet html Data can only be viewed in forms provided by Server. Data left hidden in database. Scrapers not robust or ethical.

Web Services allow 3 rd parties to display data how ever they want Database Service Servlet AServlet CServlet B xml html

Examples  Bookstores Using Amazon API  If Google Scholar had a service, could develop graph view, etc.

Web Services Allow for Aggregators Database A Database BDatabase C Database D Service B Service A Service C Service D Aggregator Servlet html xml

Competing Web Service Standards  XML-RPC  SOAP (along with WSDL, UDDI) Microsoft and IBM strong backers Popular in B2B More overhead Complex Data types XML spec facilitates automated service discovery Better tool support, currently.  REST Gaining Popularity Hacker/Blogger Crowd Little ovehead, String oriented (no complex data) Automated discovery???

WSDL, SOAP, UDDI  WSDL – Web Service Description Language  SOAP – Simple Object Access Protocol  UDDI – Universal Description, Discovery, and Integration

IDE Support Programmer writes class in favorite language Programmer marks as “web service” IDE generates wsdl file and soap service walla! Writing a Service Writing a Client Programmer provides uri of some web service IDE generates client stub Programmer makes calls to service methods.

XML is the plumbing Client Server JavaC# Generated SOAP Plumbing: programmers need not worry

DOT NET DEMO  Service  Client  Display Code See Google Client Sample: v/Distributed/WebServices/VisualStudio.Net/GoogleClientForm.aspx.cs

Sample Wrappers  A Google Open Search Web Service: reDev/Distributed/WebServices/Visu alStudio.Net/GoogleWTService.asm x.cs reDev/Distributed/WebServices/Visu alStudio.Net/GoogleWTService.asm x.cs  A Feedster Wrapper: reDev/Distributed/WebServices/Visu alStudio.Net/Feedster.cs

Resources  Hello World Tutorial -- ces/VisualStudio.Net/serviceTutorial htm Google API Tutorial -- ces/VisualStudio.Net/googleClientTutorial html Hello World Tutorial Google API Tutorial O'Reilly's Visual Studio.Net Web Services O'Reilly's ASP.Net Web Forms A Directory With Various Notes on Web Services: ces/ ces/  Want to try this in Java? I have a rough draft partial tutorial using the Apache Axis tool: ces/Axis%20Java%20Web%20Services/tutorial.htm ces/Axis%20Java%20Web%20Services/tutorial.htm