What is a web service
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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. Importance of Web Services.

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What is a web service?

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What is a web service

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


Importance of web services

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.”


Without web services content and presentation mixed

Without Web Services:Content 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


Web services allow 3 rd parties to display data how ever they want

Web Services allow 3rd parties to display data how ever they want

html

html

html

Servlet A

Servlet B

Servlet C

xml

xml

xml

Service

Database


Examples

Examples

  • Bookstores Using Amazon API

  • If Google Scholar had a service, could develop graph view, etc.


Web services allow for aggregators

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


Competing web service standards

Competing Web Service Standards

  • WSDL, SOAP, UDDI

  • REST

  • XML-RPC


Wsdl soap uddi

WSDL, SOAP, UDDI

  • WSDL – Web Service Description Language

  • SOAP – Simple Object Access Protocol

  • UDDI – Universal Description, Discovery, and Integration


Ide support

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.


Xml is the plumbing

XML is the plumbing

Server

Client

Java

C#

Generated SOAP

Generated SOAP

Plumbing: programmers need not worry


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