Development and Development and Deployment of Deployment of Web Services Web Services

What is Web service ?• Method of communication between two electronic

devices over the web

• A service that is "always on”

• W3C definition– a software system designed to support interoperable 

machine-to-machine interaction over a network.

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• It has an interface described in a machine-processable format (WSDL)

• Other systems interact with the Web service using

SOAP messages

• Features of Web Services– Language Independent

– Operating System Independent

More about Web service

Web service Platform elements

• SOAP is a simple protocol for exchange of information.

• UDDI is a specification designed to allow businesses of all sizes to benefit in the new digital economy.

• WSDL defines the XML grammar for describing services as collections of communication endpoints capable of exchanging messages.

Communication between Web-Service and heterogeneous clients

Web Service Architecture

WSDL

• WSDL is written in XML• used to describe & locate Web servicesWSDL Ports• The <portType> element is the most

important WSDL element.• It defines a web service,

the operations that can be performed, and the messages that are involved.

Type DefinitionOne-way The operation can receive a message but

will not return a responseRequest-response The operation can receive a request and will

return a responseSolicit-response The operation can send a request and will

wait for a responseNotification The operation can send a message but will

not wait for a response

Operation Types

The request-response type is the most common operation type, but

WSDL defines four types:

PortType

<portType name="glossaryTerms">  <operation name="getTerm">    <input message="getTermRequest"/>    <output message="getTermResponse"/>  </operation></portType>

UDDI

• Universal Description, Discovery and Integration (UDDI)

• UDDI is a directory for storing information about web services

• UDDI is a directory of web service interfaces described by WSDL

• UDDI communicates via SOAP• UDDI uses WSDL to describe interfaces to

web services

SOAP-based communication

SOAP:• Data in a well-defined XML format• Transport over various protocols

• HTTP, SMTP are the most used• Server side: either an RPC call or a message

delivered

SOAP Elements• Envelope (mandatory)

– Top element of the XML document representing the message.

• Header (optional)– Determines how a recipient of a SOAP message should

process the message– Adds features to the SOAP message such as

authentication, transaction management, payment, message routes, etc…

• Body (mandatory)– Exchanges information intended for the recipient of the

message. – Typical use is for RPC calls and error reporting.

<SOAP-ENV:Envelope

xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”

SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”>

<SOAP-ENV:Header>

<t:transId xmlns:t=“http://a.com/trans”>345</t:transId>

</SOAP-ENV:Header>

<SOAP-ENV:Body>

<m:Add xmlns:m=“http://a.com/Calculator”>

<n1>3</n1>

<n2>4</n2>

</m:Add>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

SOAP Request

SOAP Response

<SOAP-ENV:Envelope

xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/”

SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”>

<SOAP-ENV:Header>

<t:transId xmlns:t=“http://a.com/trans”>345</t:transId>

</SOAP-ENV:Header>

<SOAP-ENV:Body>

<m:AddResponse xmlns:m=“http://a.com/Calculator”>

<result>7</result>

</m:AddResponse>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

SOAP Fault

• Used to carry error and/or status information within a SOAP message

• Appears within the SOAP body• Defines the following:

– faultcode (mandatory)• algorithmic mechanism for identifying the fault • defined in the SOAP spec

– Faultstring (mandatory)• human readable explanation of the fault

SOAP Fault

– faultactor (optional)• information about who caused the fault to

happen • URI value identifying the source

– Detail• error information related only to the Body

element. • if not present then indicates that the fault is

not related to the Body element.

SOAP Fault Example

<SOAP-ENV:Envelope xmlns:SOAP-ENV=“http://schemas.xmlsoap.org/soap/envelope/” SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/”> <SOAP-ENV:Body> <SOAP-ENV:Fault> <faultcode>SOAP-ENV:Server</faultcode> <faultstring>Internal Application Error</faultstring> <detail xmlns:f=“http://www.a.com/CalculatorFault”> <f:errorCode>794634</f:errorCode> <f:errorMsg>Divide by zero</f:errorMsg> </detail> </SOAP-ENV:Fault> </SOAP-ENV:Body></SOAP-ENV:Envelope>

XML Messaging Using SOAP

JSON

• Java Script Object Notation

• A new ”fat“ free alternative to XML

• Much smaller grammar

• Maps more directly onto the data structures used in modern programming languages

• JSON has the same interoperability potential as XML

JSON Objects and JSON Arrays

• JSON values can be• Number, string, Boolean or null value

• JSON Objects• Contains multiple name value pairs

• JSON Array• Contains multiple JSON objects

JSON code example

{"employees": [

{ "firstName":"John" , "lastName":"Doe" }, { "firstName":"Anna" ,

"lastName":"Smith" }, { "firstName":"Peter" , "lastName":"Jones" }

]}

Deploying a Web Service

Web deploying tools

• Web Deploy for Microsoft IIS• Web Sphere for IBM servers• Axis• UDDI4J• Ivory

A more specific example

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