Web service
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Web Service. What exactly are Web Services? To put it quite simply, they are yet another distributed computing technology (like CORBA, RMI, EJB, etc.). They allow us to create client/server applications. E.G - Given a ZIP code, will provide the weather information for that ZIP code.

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Web service

Web Service

What exactly are Web Services?

To put it quite simply, they are yet another distributed computing technology (like CORBA, RMI, EJB, etc.). They allow us to create client/server applications.

E.G - Given a ZIP code, will provide the weather information for that ZIP code.

“Websites for humans, Web Services for software”


Concept of web services

Concept of web services

"Hey! Wait a moment! I can do that with RMI, CORBA, EJBs, and countless other technologies!" So, what makes Web Services special? Well, Web Services have certain advantages over other technologies


Advantages of web services

Advantages of Web Services

  • Web Services are platform-independent and language-independent, since they use standard XML languages. This means that my client program can be programmed in C++ and running under Windows, while the Web Service is programmed in Java and running under Linux.

  • Most Web Services use HTTP for transmitting messages (such as the service request and response). This is a major advantage if you want to build an Internet-scale application, since most of the Internet's proxies and firewalls won't mess with HTTP traffic (unlike CORBA, which usually has trouble with firewalls).


Disadvantages of web services

Disadvantages of Web Services

  • Overhead Transmitting all your data in XML is obviously not as efficient as using a proprietary binary code. What you win in portability, you lose in efficiency. Even so, this overhead is usually acceptable for most applications, but you will probably never find a critical real-time application that uses Web Services.

  • Lack of versatility Currently, Web Services are not very versatile, since they only allow for some very basic forms of service invocation.


Important characteristic

Important characteristic

  • While technologies such as CORBA and EJB are geared towards highly coupleddistributed systems, where the client and the server are very dependent on each other

  • Web Services are more adequate for loosely coupledsystems, where the client might have no prior knowledge of the Web Service until it actually invokes it.

  • Highly coupled systems are ideal for intranet applications, but perform poorly on an Internet scale.

  • Web Services, however, are better suited to meet the demands of an Internet-wide application, such as grid-oriented applications.


Web services addressing

Web Services Addressing

  • The discovery registry might have replied with the following URI:

    http://webservices.mysite.com/weather/us/WeatherService


A typical web service invocation

A Typical Web Service Invocation


Web services architecture

Web Services Architecture


Web service integration

Web Service Integration

  • Connect (HTTP or SMTP)

  • Find (UDDI)

  • Define (WSDL)

  • Transact (SOAP)


Server side

Server side


Web service

SOA

  • Service-Oriented Architecture (SOA) is a set of principles and methodologies for designing and developing software in the form of interoperable services.

  • services are well-defined business functionalities that are built as software components (discrete pieces of code and/or data structures) that can be reused for different purposes.

  • SOA defines how to integrate widely disparate applications for a Web-based environment and uses multiple implementation platforms. Rather than defining an API, SOA defines the interface in terms of protocols and functionality


Web service

  • Service orientation requires loose coupling of services with operating systems, and other technologies that underlie applications.

  • SOA is concept from Distributed Computing

  • Now SaaS, Cloud Computing uses SOA


Web service

  • Web services are in use to implement SOA


What is soap simple object access protocol

What is SOAP?Simple Object Access Protocol

  • A lightweight mechanism to exchange structured and typed information.

  • A wire protocol similar to the IIOP,ORPC,JRMP.

  • A simple mechanism to express application semantics.

  • The above mentioned features allow SOAP to be used in a large variety of systems ranging from messaging systems to remote procedure calls (RPC)


Web service

  • SOAP has three major characteristics:

    • Extensibility (security and WS-routing are among the extensions under development),

    • Neutrality (SOAP can be used over any transport protocol such as HTTP, SMTP or even TCP), and

    • Independence (SOAP allows for any programming model).


Web service

  • This XML based protocol consists of three parts:

    • an envelope, which defines what is in the message and how to process it,

    • a set of encoding rules for expressing instances of application-defined datatypes, and

    • a convention for representing procedure calls and responses.


Sample soap xml

Sample SOAP XML

<?xml version="1.0"?>

<soap:Envelope

xmlns:soap="http://www.w3.org/2001/12/soap-envelope"

soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">

<soap:Header>

...

...

</soap:Header>

<soap:Body>

...

...

<soap:Fault>

...

...

</soap:Fault>

</soap:Body>

</soap:Envelope>


Sample soap xml1

Sample SOAP XML

REQUEST

<soap:Body>

<m:GetPrice xmlns:m="http://www.bse.co.in/prices">

<m:Symbol>TCS</m:Symbol>

</m:GetPrice>

</soap:Body>

RESPONSE

<soap:Body>

<m:GetPriceResponse xmlns:m="http://www.bse.co.in/prices">

<m:Price>1280.40</m:Price>

</m:GetPriceResponse>

</soap:Body>

Only the Body part of the SOAP XML is shown here


Web service description language wsdl

Web Service Description Language (WSDL)

  • WSDL is an XML grammar for describing a web service as a collection of access end points capable of exchanging messages in a procedure or document-oriented fashion.

  • WSDL describes what a service does, how to invoke its operations and where to find it.

  • A WSDL document is a recipe used to automate the details involved in application-to-application communication.


Universal description discovery and integration uddi

Universal Description Discovery and Integration (UDDI)

  • UDDI provides a standardized method for publishing and discovering information about web services. The UDDI project is an industry initiative that attempts to create a platform-independent, open framework for describing services, discovering businesses and integrating business services.

  • UDDI is a centrally accessible registry of services.


Uddi registry

White Pages

Service Broker

Service Requestor

Yellow Pages

Green Pages

Service Provider

UDDI Registry

UDDI Registry steps :

2. Searches business description and services

3. Discovery of service’s functional and technical details

1. Register the Web Service

4. Integrate the Service into User Application dynamically


Web service

UDDI

Conceptually, a business can register three types of information into a UDDI registry. The specification does not call out these types specifically but they provide a good summary of what UDDI can store for a business.

  • White pages

    Basic contact information and identifiers about a company, including business name, address , contact information and unique identifiers such as tax Ids. This information allows others to discover your web service based upon your business identification.

  • Yellow pages

    Information that describes a web service using different categorizations. This information allows others to discover your web service based upon its categorization.

  • Green pages

    Technical information that describes the behaviors and supported functions of a web service hosted by your business. This information includes pointers to the grouping information of web services and where the web services are located.


Web service

SaaS

  • Software as a Service

  • Cloud Computing – utility computing


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