DOT NET WEB SERVICES Agenda

1
DOT NET WEB SERVICESAgenda

• Web Services Discussion
• Quick DOT NET DEMO
• Assignment
• Lab Hello World Service/Client
• Lab Google Client
• Lab Open Search Info Source

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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.
3
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?

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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

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Without Web ServicesContent and Presentation
mixed

• Data can only be viewed in forms provided by
  Server.
• Data left hidden in database.
• Scrapers not robust or ethical.

html
Servlet
Database
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Web Services allow 3rd parties to display data
how ever they want
html
html
html
Servlet A
Servlet C
Servlet B
xml
xml
xml
Service
Database
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Examples

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

8
Web Services Allow for Aggregators
html
Aggregator Servlet
xml
xml
xml
xml
Service D
Service A
Service C
Service B
Database A
Database D
Database B
Database C
9
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???

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WSDL, SOAP, UDDI

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

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IDE Support
Writing a Service

• Programmer writes class in favorite language
• Programmer marks as web service
• IDE generates wsdl file and soap service
• walla!

Writing a Client

• Programmer provides uri of some web service
• IDE generates client stub
• Programmer makes calls to service methods.

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XML is the plumbing
Server
Client
Java
C
Generated SOAP
Generated SOAP
Plumbing programmers need not worry
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DOT NET DEMO

• Service
• Client
• Display Code
• See Google Client Sample
• http//cs.usfca.edu/wolber/SoftwareDev/Distribute
  d/WebServices/VisualStudio.Net/GoogleClientForm.as
  px.cs

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Sample Wrappers

• A Google Open Search Web Servicehttp//cs.usfca.
  edu/wolber/SoftwareDev/Distributed/WebServices/Vi
  sualStudio.Net/GoogleWTService.asmx.cs
• A Feedster Wrapperhttp//cs.usfca.edu/wolber/So
  ftwareDev/Distributed/WebServices/VisualStudio.Net
  /Feedster.cs

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Resources

• Hello World Tutorial -- http//www.cs.usfca.edu/w
  olber/SoftwareDev/Distributed/WebServices/VisualSt
  udio.Net/serviceTutorial3.7.05.htmGoogle API
  Tutorial -- http//www.cs.usfca.edu/wolber/Softwa
  reDev/Distributed/WebServices/VisualStudio.Net/goo
  gleClientTutorial3.7.05.html
• O'Reilly's Visual Studio .Net Web
  ServicesO'Reilly's ASP.Net Web Forms
• A Directory With Various Notes on Web Services
  http//www.cs.usfca.edu/wolber/SoftwareDev/Distri
  buted/WebServices/
• Want to try this in Java? I have a rough draft
  partial tutorial using the Apache Axis tool
  http//www.cs.usfca.edu/wolber/SoftwareDev/Distri
  buted/WebServices/Axis20Java20Web20Services/tut
  orial.htm