An Introduction to Web Services

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3 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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An Introduction to Web Services

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Objectives


Discuss distributed computing


Explain web services and their characteristics


Discuss the generic architecture of web
services


Describe the life cycle of a web service


Identify the requirements for a web service


Explain the working of a web service


Discuss the advantages and disadvantages of
web services


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Component Architecture

Components

Method 1……


User submits


parameters

Appropriate

Method called

Returns


the result

Application


Method 2……


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Application

Computing Over the Years (1)

Database

Stand
-
alone Computers

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Client
-
Server Computing

Server

Clients: Smart terminals

PC

Computing Over the Years (2)

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Distributed Computing

Smart terminals

Distributed Computing

Component A

Windows OS

Component B

Component F

Linux OS

Component C

Component D

Component E

Distributed Component Architectures


The three main Distributed Component
Architectures are:


CORBA

Developed by OMG

DCOM

Developed by Microsoft

RMI

Developed by SUN. Uses CORBA for Heavy
-
Duty
Distributed Systems

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Inter
-
Module Communication

Application developed using C#

Application developed using VB.net

Inter
-
Module communication needs:

1. Set of rules for communication

2. Standard Language for interfaces

3. Interfaces for the modules

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Web
-
based Applications


Must be simple, self explanatory and easy to use

Services Offered

e
-
mail, browsing, searching the net, chat applications

Devices Used to Access the Web

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Web Services

Network may be LAN, WAN, MAN or Internet


Web Services: Internet based modular applications

Web Service

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Web Services Solutions

Two of the most popular Web Services Solutions

SUN
TM

OPEN NET ENVIRONMENT (SUN ONE)

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Web Service Example

EMI Calculator Web Service

Loan Application Using

Web Service

Running on

Another Web


Service

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Characteristics of Web Services

Should be registered

Uses XML

Uses standard


web protocols

Accessed over the web

Has a service interface

Supported by loosely coupled
applications

Integrated Just In Time

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Important Components

Service


Broker

Service

Requestor

Service

Provider

Service

Registry

Publish

Find

Bind

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Web Services: Generic Architecture

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Life Cycle

1. Create a web service

2. Define service interface, invocation methods for the web service

3. Publish the web service on the Internet or Intranet


5. Invoke the web service


6. Unpublish the web service when not needed


4. Search for the web service


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Requirements for a Web Service

XML: Represent data in a standard format

SOAP: Common extensible message format

WSDL: Common, extensible, service description language


UDDI: Maintains registries storing information about

service providers and their services


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Working of a Web Service

Soap Protocol

XML over HTTP

Parameters

Return Value

Service Description

Web Server


(With Web Service)

Client Application

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Accessing Web Services over HTTP

HTTP GET operation

HTTP POST operation

SOAP

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Business Process

Web Service

Organization A

Organization B

Advantages of Web Services


Cross business integration


Improved efficiency


Closer customer relationships


Facilitates just
-
in
-
time integration


Reduces complexity


Legacy applications



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Constraints


Businesses not willing

to expose the
functionalities


The
only technology

that forms the base
is

XML
, that means we cannot do without
XML


The

cost

involved is very

high