Introduction to Web Services

Presented by

Sarath Chandra Dorbala

Outline

Definitions Basic Standards SOAP WSDL UDDI

Definitions

A Web Service is a software component that is described via WSDL and is capable of being accessed via standard network protocols such as but not limited to SOAP over HTTP.www.oasis-open.org/committees/wsia/glossary/wsia-draft-glossary-03.htm

The W3C defines a Web service as a software system designed to support interoperable Machine to Machine interaction over a network. http://en.wikipedia.org/wiki/Web_service

An Internet hosted application controlled through SOAP requests which returns results as SOAP responses. http://www.gateway2sms.com/glossary.asp

Basic Standards

XML– All web service documents are written in XML– XML Schemas are used to define elements used in Web

Service communication

SOAP– Communication is done over SOAP (typically)– Request and responses messages are encoded in SOAP– The body of the message is contained with in SOAP

envelope– Binds the client to the web service

WSDL– Describes the web service and defines functions that are exposed

in the web service– Defines SOAP message format

UDDI– UDDI is used to register and look up services with a central

registry– Service Providers can publish information about their business and

the services that they offer– Service consumers can look up services that are available by

Business Service category Specific service

SOAP

Stands for Simple Object Access Protocol It is a platform independent, XML bases

communication protocol for message exchanging between applications

Elements of SOAP message

SOAP is a XML document with the following elements

Envelope– Used to identify the SOAP message

Header (Optional)– This element contains header. For this course this part is

important for incorporating security into web services Body

– This element contains call and response information Fault (Optional)

– This element contains details about processing errors

Skeleton SOAP Message

<?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 Message

SOAP Request

POST /InStock HTTP/1.1Host: www.example.orgContent-Type: application/soap+xml; charset=utf-8Content-Length: nnn

<?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:Body xmlns:m="http://www.example.org/stock">

<m:GetStockPrice><m:StockName>IBM</m:StockName>

</m:GetStockPrice></soap:Body></soap:Envelope>

SOAP Response

HTTP/1.1 200 OKContent-Type: application/soap+xml; charset=utf-8Content-Length: nnn

<?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:Body xmlns:m="http://www.example.org/stock">

<m:GetStockPriceResponse><m:Price>34.5</m:Price>

</m:GetStockPriceResponse></soap:Body></soap:Envelope>

WSDL

WSDL stands for Web Service Description Language

It is an XML Document that describes a web service

It specifies the location of the service and operations it exposes

Elements of WSDL

<portType>– It describes a web service, the operations that can be

performed, and the messages that are involved. <message>

– Defines the data elements of an operation. Eg, Parameters to the function call parameters

<types>– Defines the data types used by the web service

<binding>– Defines the message format and protocol bindings for each

port

Skeleton WSDL Document

<definitions><types>

definition of types........</types><message>

definition of a message....</message><portType>

definition of a port.......</portType><binding>

definition of a binding.... </binding></definitions>

WSDL Binding to SOAP

UDDI

UDDI stands for Universal Description, Discovery and Integration

UDDI is a platform-independent framework for describing services, discovering businesses, and integrating business services by using the Internet.

Advantages of UDDI

Finding the right business from millions Defines how to enable e-commerce once

business is found Describing services and business processes

programmatically in a single, open and secure environment.

Basic Mechanism

Conclusions

We have seen the essential components of a Web Service.

We have seen the brief overview of these components that form the building blocks of a web service

Recommendations

Examine the real WSDL documents and realize its components

Here is a sample WSDL

http://cs.odu.edu/~sdorbala/wsdl/joft.wsdl Tutorials for creating web services both in .NET and

in Java are availablehttp://cs.odu.edu/~sdorbala/ws/JavawebInstr.pdf

http://cs.odu.edu/~sdorbala/ws/instructions_net2003.pdf

References

http://wikipedia.org/wiki/Web_service http://w3schools.com

Questions