Distributed Information Systems Lecture 17 - SOA, Lecture notes of Computers and Information technologies

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Service Oriented

Architectures (SOA)

Dr Liz Bacon

Overview

• Web Services• Example implementation• Benefits of a SOA architecture• SOA Management• SOA workflow and Orchestration• SOA issues and research areas •

Ack: Peter Morris and Gill Windall for some of the thesenotes.

What makes the web popular for

human users?

• Ease of use• Ubiquity• Size and diversity of content• Searchability • Web services are about trying to make

those advantages availableto

software

using other

software

to perform

services for it

What sort of services?

• Well anything .... translate from Russian toEnglish

foreign currencyconversion

calculate income tax

perform scientificcalculations

get weather forecast

get latest share prices

convert a postcode togeographic coordinates^ order spare parts

plan cheapest air routebetween two locations

etc etc etc

My

holiday

webpage

Travel company

web server

exchange rates

comparisonweb service

weather forecastingweb service

ticket agency

web service

Amazon's web service

Web Service Scenario Two

Car manufacturer

Two of their internal systems are 1) parts controland 2) scheduling of production.

They would like to keep their stock of parts to aminimum but of course they must never run out.

They would like to keep their dealers informedabout the availability of completed cars.

These links to suppliers and dealers used to behandled by phone calls but now they have beenautomated using web services.

This is an example of B2B integration of thesupply chain using web services.

Service-Oriented Architecture

(SOA)

An architectural style that formally separates services(i.e. functionality provided by systems) from serviceconsumers (other systems)

Separation is achieved through:

• a service contract– a way for providers to publish service contracts– a way for consumers to locate the contracts

SOA separates the contract from the implementation ofthat contract

• produces an architecture in which the coupling between the

consumer of the service and the modules that produce the workis extremely loose and easily reconfigured

Providers, brokers and users/clients

Service Provider - organisation hosting the web servicee.g. organisation providing weather forecasts

Service User - organisation/software wanting to makeuse of web services e.g. the holiday company

Service Broker - organisation that provides "yellowpages" type lookup service for web services

ServiceProvider

ServiceBroker

Service

User/Client

Find

Bind and Invoke

Publish

Mapping technologies to roles

Service Provider

SOAP service WSDL description

Service Broker

UDDI registry

Service User/Client

Find

Publish

Bind

and

Invoke

SOAP client

Are public Web Services available

now?

Yes lots e.g.

Amazon

Google

and

eBay

have all launched

Web Service interfaces to their services

• Amazon
• product catalogue and sales etc
  • Google
  • search engine and other services
    • eBay
    • buy and sell items

Publicly searchable (human-readable andmachine-readable) directories e.g.

http://www.xmethods.net/

• You search for a service and then view the WSDL

How to run it

• Save file as Hello.asmx• Put it in the web route directory of your IIS

server e.g. C:\Inetpub\wwwroot

• Surf to is as

http://localhost/Hello.asmx

• You should see something like the

following:

Result is returned in XML format

That doesn't look like a SOAP message!

It's not. .NET web services can be tested viaplain HTTP (i.e. REST style) bindings

Calculator Web Service – in Notepad

<%@ WebService Class="CalculatorService " Language="c#"%>using System.Web.Services;public class CalculatorService : WebService{

private int result = 0;[WebMethod]public int add(int i1, int i2){

result = i1 + i2;return result;

} [WebMethod]public int subtract(int i1, int i2){

result = i1 - i2;return result;

}

}