Introduction to Web Services[2]

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Introduction to Web Services

Saturday, October 29, 2011


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What is Web Service?

! Currently, most websites limit themselves toextremely simple methods of integration.

!you might be provided with a link that opensanother website in an existing frame on thecurrent web page.

!

Most important, units of application logic canteasily be reused between one application andanother.



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The Web Today: The Human Centric

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Web Services: Application Centric Web

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Operating System: Linux



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Uses of Web Services

! Business#to#Business

! Electronic Data Interchange !EDI"has been thetechnology of choice.

! EDI has been a technology that only largecorporations could a$ord to leverage.

! XML could facilitate the low#cost and simplisticapproach that was necessary for the B2B task.



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! Exposing Functionality to Customers

!

An example might be the history report of a carbut not just any report, especially not one that isdisplayed in a Web page.

! Rather, this information must be provided in

XML so that a car dealer can build a used#carevaluation system that automatically approves or

rejects trade#ins.



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! Integrating Heterogeneous Systems

! It's normal for companies to have computingsystems dispersed across multiple platforms.

!Web Services is the solutions for these problems



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!Rapid Development Environment!Web Services can make your project

development environment operate faster!

Developers can work in their preferredenvironment, while still allowing them toproduce an integrated solution.

!Web Services also force you to think in terms of

interfaces.!You don't have to worry about compiling

another developer's source code or linking inlibraries.



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Web Service Architecture

!Web Services Role!Service Provider

!

This is the provider of the web service. Theservice provider implements the service andmakes it available on the Internet.

!Service Requestor!

This is any consumer of the web service. Therequestor utilizes an existing web service byopening a network connection and sending anXML request.



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! Service Registry

!This is a logically centralized directory ofservices. The registry provides a central place

where developers can publish new services orfind existing ones. It therefore serves as a

centralized clearinghouse for companies andtheir services.



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!Web Services Protocol Stack !4 layers"!Service Transport

!

This layer is responsible for transportingmessages between applications.Currently, this layer includes hypertexttransfer protocol !HTTP", Simple Mail

Transfer Protocol!SMTP

", file transferprotocol !FTP", and newer protocols,

such as Blocks Extensible ExchangeProtocol !BEEP".



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!XML Messaging!This layer is responsible for encoding messagesin a common XML format so that messages

can be understood at either end. Currently,this layer includes XML#RPC and SOAP.!Service Description

!This layer is responsible for describing the

public interface to a specific web service.Currently, service description is handled viathe Web Service Description Language!WSDL".



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! Service Discovery

!This layer is responsible for centralizingservices into a common registry, and providingeasy publish/find functionality. Currently,service discovery is handled via Universal

Description, Discovery, and Integration!UDDI".



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Service Transport

! HTTP

! HTTP is the most popular of Web services

transport! HTTP is simple, stable, and widely deployed

! HTTP is allowed by Firewall

!Allows XML, XML#RPC! Security Concern



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XML Messaging

! XML !eXtension Markup Language"! Mid#1970s, Charles F Goldfarb introduce theworld of Standard Generalized Markup Language!SGML". It is designed for data representation.

! HTML !Hyper Text Markup Language"is basedon SGML. It is describe how to formatting andpresent the data



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XML Messaging

! XML !eXtension Markup Language"

! Mid#1970s, Charles F Goldfarb introduce theworld of Standard Generalized Markup Language!SGML". It is designed for data representation.

! HTML !Hyper Text Markup Language"is based

on SGML. It is describe how to formatting andpresent the data



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XML Messaging

! XML !eXtension Markup Language"!XML is really just a collection of data consisting

of both physical and logical structure.!

Physically, the document consists of textualinformation. It contains entities that canreference other entities that are locatedelsewhere in memory, on a hard disk, or, more

importantly, on the Web.!The logical structure of an XML document

includes processing instructions, declarations,comments, and elements.



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XML Messaging

! XML !eXtension Markup Language"

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XML Messaging

! XML#RPC !Remote Procedure Call"

!

It is the simple protocol that uses XMLmessaging for perform RPC.

! Message send via HTTP POST.

!

XML#RPC is platform independent. JAVA clientcan sent XML#RPC for call .NET Server.



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XML Messaging

!XML#RPC !Request"

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XML Messaging

!XML#RPC !Response"

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XML Messaging

! SOAP !Simple Object Access Protocol"!SOAP is an XML#based protocol for

exchanging information between computers.!SOAP can be used in a variety of messaging

systems, and can be delivered via a variety oftransport protocols, the main focus of SOAP is

RPCs transported via HTTP.!Like XML#RPC, SOAP is platform#

independent and therefore enables diverseapplications to communicate.



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XML Messaging

! SOAP (Request)

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XML Messaging

! SOAP (Response)

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Service Description: WSDL

!WSDL !Web Services Description Language"!WSDL is an XML grammar for specifying a

public interface for a web service.!Information on all publicly available functions.!Data type information for all XML message.!Biding information about the specific transport

protocol to be used.!Address information for locating thespecifiedservice.

!Describing of SOAP Services



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Service Description: WSDL

! WSDL !Example"



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Service Discovery: UDDI

! Universal Description, Discovery, and Integration

! UDDI is was originally created by Microsoft, IBM and

Ariba! UDDI is the place the to find and discover the Web

Service

!

Public UDDI or Private UDDI !Public: http://uddi.microsoft.com"



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Security Consideration

!Confidential!both XML#RPC and SOAP run primarily

on top of HTTP, and XML

communications can therefore beencrypted via the Secure Sockets Layer!SSL". SSL is a proven technology, is widelydeployed, and is therefore a very viable

option for encrypting messages.!Authentication!Network Security



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Security Consideration

!Authentication

!One solution is to leverage HTTPauthentication. HTTP includes built#in

support for Basic and Digestauthentication, and services can thereforebe protected in much the same manner as

HTML documents are currentlyprotected. Most security experts, however,agree that HTTP authentication is arelativel weak o tion.



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All Together

! Services Provider



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All Together

! Services Requestor



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Question & Answer



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