Download Introduction to ASP.NET

Creating & Consuming Web
Services
MIS 424
Professor Sandvig
Overview – Web Services
What are Web Services?
Benefits
Who is using them
Using in .NET
– How to create
– How to consume
What are Web Services?
Web services allow applications to communicate
with each other via Internet
Islands of data
Huge databases
– Every large organization
– Can’t communicate, share
Between organizations
Within organizations
What are Web Services?
Underlying Technologies
– XML
Defines data content
– SOAP
Simple object access protocol
– Protocol  rules
Advantage
– HTTP: name-value pairs
– SOAP:
data relationships
Data types
Both are W3.org standards
– Supported by all major vendors
Why Now?
Historically
– Physical distance
– Small data pipelines
Now
– Internet, fiber optics, …
– Distance not a problem
Recent: mid-1990’s
Limitation
– Need common language & protocols
Solution
– Web Services: XML & Soap
Who is using?
Amazon
– Retrieve shipping info
– Expose product database
UPS
– Shipping status, pricing information, etc.
Google
– Expose database
– Tap creativity of programmers
Ideas for free
Others??
– Difficult to tell, background process
Overstock.com web site
Using Web Services in .NET
Web Service Namespaces
– Implements XML & SOAP technologies
– Dozens of classes
High level
Handle messy details
– MSDN Documentation
Heavily promoted functionality of .NET
Using Web Services
Two roles:
– Create
Expose your data/application to other
– Consume
Utilize web services offered by others
Creating Web Services
Visual Studio:
– Add new item: Web Service
.asmx file
Creating Web Service
Default .asmx file:
Creating Web Services
Example:
Testing
– Via HTTP
Request .asmx file
– CreateWebService.asmx, (source .doc)
Consuming Web Service
Create proxy
– Visual Studio
1. Add service reference…
2. Paste in web service
description language (wsdl)
–
VS creates classes that utilize
service
3. Use like any other classes
Consuming Web Service
Visual Studio
Paste web
service URL
Consuming Web Service
WSDL
returns
service
description:
– Give
descriptive
name and
click OK
Consuming Web Service
Visual Studio creates class
(proxy) representing web
service
Adds info to web.config
Consuming Web Services
Service now represented by class
Service methods visible via Intellisense
Consuming Web Service
Example:
– ConsumeWebService.aspx
– .asmx files can handle AJAX calls
See assignment 4
– ObjectDataSource control:
Use VS wizard to select web service class
Summary – Web Services
Allow applications to communicate
– Connect islands of data
Based upon W3 standards
.NET support
– Very easy to publish & consume