Introduction to Web Services Yossi Amir Itzik Kasovitch.

Introduction to Web Introduction to Web ServicesServices

Yossi AmirYossi Amir

Itzik KasovitchItzik Kasovitch

AgendaAgenda

MotivationMotivation HistoryHistory Web service modelWeb service model Web service componentsWeb service components A walkthrough examplesA walkthrough examples

MotivationMotivation

The ability to program the Web.The ability to program the Web. Example: Consider an Excel spreadsheet that Example: Consider an Excel spreadsheet that

summarizes your whole financial picture : summarizes your whole financial picture : stocks, bank accounts, loans, etc. If some of stocks, bank accounts, loans, etc. If some of this information is available through XML this information is available through XML Web services, Excel can update it and Web services, Excel can update it and present the update information to the user. present the update information to the user.

Web Service definitionWeb Service definition

A simple definition:A simple definition:

““a Web Service is an application component a Web Service is an application component accessible over open protocols”.accessible over open protocols”.

HistoryHistory

Web services evolved from previous Web services evolved from previous technologies that served the same purpose technologies that served the same purpose such as RPC, ORPC (DCOM, CORBA and such as RPC, ORPC (DCOM, CORBA and JAVA RMI).JAVA RMI).

Web Services were intended to solve three Web Services were intended to solve three main problems:main problems:

1.1. InteroperabilityInteroperability2.2. Firewall traversalFirewall traversal3.3. ComplexityComplexity

InteroperabilityInteroperability

Earlier distributed systems suffered from Earlier distributed systems suffered from interoperability issues because each vendor interoperability issues because each vendor implemented its own onimplemented its own on--wire format for wire format for distributed object messagingdistributed object messaging. .

Development of DCOM apps strictly bound to Development of DCOM apps strictly bound to Windows Operating system.Windows Operating system.

Development of RMI bound to Java Development of RMI bound to Java programming language.programming language.

Firewall traversalFirewall traversal

Collaboration across corporations was an issue Collaboration across corporations was an issue because distributed systems such as CORBA because distributed systems such as CORBA and DCOM used nonand DCOM used non--standard portsstandard ports..

Web Services use HTTP as a transport Web Services use HTTP as a transport protocol and most of the firewalls allow access protocol and most of the firewalls allow access though port 80though port 80 ( (HTTPHTTP)), leading to easier and , leading to easier and dynamic collaborationdynamic collaboration..

ComplexityComplexity

Web Services is a developerWeb Services is a developer--friendly service friendly service systemsystem. .

Most of the aboveMost of the above--mentioned technologies mentioned technologies such as RMI, COM, and CORBA involve a such as RMI, COM, and CORBA involve a whole learning curve.whole learning curve.

New technologies and languages have to be New technologies and languages have to be learnt to implement these serviceslearnt to implement these services..

Web Service definition revisitedWeb Service definition revisited

A more precise definition:A more precise definition: an application component thatan application component that: :

Communicates via open protocols (HTTP, SMTP, etc.) Communicates via open protocols (HTTP, SMTP, etc.) Processes XML messages framed using SOAP Processes XML messages framed using SOAP Describes its messages using XML Schema Describes its messages using XML Schema Provides an endpoint description using WSDL Provides an endpoint description using WSDL Can be discovered using UDDICan be discovered using UDDI

Web Services ComponentsWeb Services Components

XMLXML – eXtensible Markup Language – A uniform – eXtensible Markup Language – A uniform data representation and exchange mechanism.data representation and exchange mechanism.

SOAPSOAP – Simple Object Access Protocol – A standard – Simple Object Access Protocol – A standard way for communication.way for communication.

UDDIUDDI – Universal Description, Discovery and – Universal Description, Discovery and Integration specification – A mechanism to register Integration specification – A mechanism to register and locate WS based application.and locate WS based application.

WSDLWSDL – Web Services Description Language – A – Web Services Description Language – A standard meta language to described the services standard meta language to described the services offered. offered.

Example – A simple Web ServiceExample – A simple Web Service

A buyer (which might be a simple client) is ordering goods A buyer (which might be a simple client) is ordering goods from a seller service.from a seller service.

The buyer finds the seller service by searching the UDDI The buyer finds the seller service by searching the UDDI directory. directory.

The seller service is a Web Service whose interface is defined The seller service is a Web Service whose interface is defined using Web Services Description Language (WSDL).using Web Services Description Language (WSDL).

The buyer is invoking the order method on the seller service The buyer is invoking the order method on the seller service using Simple Object Access Protocol (SOAP) and the WSDL using Simple Object Access Protocol (SOAP) and the WSDL definition for the seller service.definition for the seller service.

The buyer knows what to expect in the SOAP reply message The buyer knows what to expect in the SOAP reply message because this is defined in the WSDL definition for the seller because this is defined in the WSDL definition for the seller service.service.

The Web Service ModelThe Web Service Model

The Web Services architecture is based upon The Web Services architecture is based upon the interactions between three roles:the interactions between three roles: Service providerService provider Service registryService registry Service requestorService requestor

The interactions involve the:The interactions involve the: Publish operationsPublish operations Find operationFind operation Bind operations.Bind operations.

The Web Service Model (cont)The Web Service Model (cont)

The Web Services model follows the The Web Services model follows the publishpublish, , findfind, and , and bindbind paradigm. paradigm.

1. publish1. publish 2. find2. find

3. bind/invoke3. bind/invoke

Web ServiceRegistry

Web Service Provider

Web Service Client

XMLXML

XML stands for EXML stands for EXXtensible tensible MMarkup arkup LLanguage. anguage.

XML is a XML is a markup languagemarkup language much like much like HTML. HTML.

XML was designed to XML was designed to describe datadescribe data.. XML tags are not predefinedXML tags are not predefined. . You must You must define define

your own tags.your own tags. The prefect choice for enabling crossThe prefect choice for enabling cross--platform platform

data communication in Web Services. data communication in Web Services.

XML vs HTMLXML vs HTML

An HTML example:An HTML example:

<html><html>

<body><body>

<h2>John Doe</h2><h2>John Doe</h2>

<p>2 Backroads Lane<br><p>2 Backroads Lane<br>

New York<br>New York<br>

045935435<br>045935435<br>

[email protected]<br>[email protected]<br>

</p></p>

</body></body>

</html></html>


This will be displayed as:This will be displayed as:

HTML specifies how the document is to be displayed, HTML specifies how the document is to be displayed, and not what information is contained in the document.and not what information is contained in the document.

Hard for machine to extract the embedded information. Hard for machine to extract the embedded information. Relatively easy for human. Relatively easy for human.

John DoeJohn Doe

2 Backroads Lane2 Backroads Lane

New YorkNew York

045935435045935435

[email protected]@gmail.com


Now look at the following:Now look at the following:

In this case:In this case: The information contained is being marked, but not for The information contained is being marked, but not for

displaying. displaying. Readable by both human and machines.Readable by both human and machines.

<?xml version=1.0?><?xml version=1.0?>

<contact><contact>

<name>John Doe</name><name>John Doe</name>

<address>2 Backroads Lane</address><address>2 Backroads Lane</address>

<country>New York</country><country>New York</country>

<phone>045935435</phone><phone>045935435</phone>

<email>[email protected]</email><email>[email protected]</email>

</contact></contact>

SOAPSOAP SOAP originally stood for "Simple Object Access SOAP originally stood for "Simple Object Access

Protocol" .Protocol" . Web Services expose useful functionality to Web Web Services expose useful functionality to Web

users through a standard Web protocol called SOAP. users through a standard Web protocol called SOAP. Soap is an XML vocabulary standard to enable Soap is an XML vocabulary standard to enable

programs on separate computers to interact across programs on separate computers to interact across any network. SOAP is a simple markup language for any network. SOAP is a simple markup language for describing messages between applications. describing messages between applications.

Soap uses mainly HTTP as a transport protocol. That Soap uses mainly HTTP as a transport protocol. That is, HTTP message contains a SOAP message as its is, HTTP message contains a SOAP message as its payload section.payload section.

SOAP CharacteristicsSOAP Characteristics

SOAP has three major characteristics:SOAP has three major characteristics: Extensibility – security and WS-routing are Extensibility – security and WS-routing are

among the extensions under development.among the extensions under development. Neutrality - SOAP can be used over any transport Neutrality - SOAP can be used over any transport

protocol such as HTTP, SMTP or even TCP.protocol such as HTTP, SMTP or even TCP. Independent - SOAP allows for any programming Independent - SOAP allows for any programming

model .model .

SOAP Building BlocksSOAP Building Blocks

A SOAP message is an ordinary XML document A SOAP message is an ordinary XML document containing the following elementscontaining the following elements:: A required Envelope element that identifies the XML A required Envelope element that identifies the XML

document as a SOAP message.document as a SOAP message. An optional Header element that contains header An optional Header element that contains header

information.information. A required Body element that contains call and response A required Body element that contains call and response

information.information. An optional Fault element that provides information about An optional Fault element that provides information about

errors that occurred while processing the message. errors that occurred while processing the message.

SOAP RequestSOAP RequestPOST POST //InStock HTTPInStock HTTP//1.1 1.1

HostHost: : wwwwww..stockstock..org org

ContentContent--TypeType: : applicationapplication//soapsoap++xml; charsetxml; charset==utf-8 Contentutf-8 Content--LengthLength: 150: 150

<?xml version<?xml version="="1.01.0""?> ?>

<soap<soap::EnvelopeEnvelope

xmlnsxmlns::soapsoap="="httphttp://://wwwwww..w3w3..orgorg//2001/122001/12//soapsoap--envelopeenvelope" " soapsoap::encodingStyleencodingStyle==httphttp://://wwwwww..w3w3..orgorg//2001/122001/12//soap-encoding”>soap-encoding”>

<soap<soap::Body xmlnsBody xmlns::mm="="httphttp://://wwwwww..stockstock..orgorg//stockstock""> >

<m<m::GetStockPrice> GetStockPrice>

<m<m::StockName>IBM<StockName>IBM<//mm::StockName> StockName>

<<//mm::GetStockPrice>GetStockPrice>

<<//soapsoap::Body>Body>

</soap</soap::Envelope>Envelope>

SOAP ResponseSOAP ResponseHTTPHTTP//1.11.1 200 OK 200 OK

ContentContent--TypeType: : applicationapplication//soap; charsetsoap; charset==utf-8utf-8

ContentContent--LengthLength: 126: 126

<?xml version<?xml version="="1.01.0""?> ?>

<soap<soap::Envelope xmlnsEnvelope xmlns::soapsoap="="httphttp://://wwwwww..w3w3..orgorg//2001/122001/12//soapsoap--envelopeenvelope" " soapsoap::encodingStyleencodingStyle="="httphttp://://wwwwww..w3w3..orgorg//2001/122001/12//soapsoap--encodingencoding"">>

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

<m:GetStockPriceResponse> <m:GetStockPriceResponse>

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

</m:GetStockPriceResponse> </m:GetStockPriceResponse>

</soap:Body></soap:Body>

</soap:Envelope> </soap:Envelope>

SOAP SecuritySOAP Security

SOAP uses HTTP as a transport protocol and SOAP uses HTTP as a transport protocol and hence can use HTTP security mainly HTTP hence can use HTTP security mainly HTTP over SSL.over SSL.

But, since SOAP can run over a number of But, since SOAP can run over a number of application protocols (such as SMTP) security application protocols (such as SMTP) security had to be considered.had to be considered.

The The WS-Security specificationWS-Security specification defines a defines a complete encryption system. complete encryption system.

WSDLWSDL WSDL stands for Web Services Description Language.WSDL stands for Web Services Description Language. WSDL is an XML vocabulary for describing Web services. It WSDL is an XML vocabulary for describing Web services. It

allows developers to describe Web Services and their allows developers to describe Web Services and their capabilities, in a standard mannercapabilities, in a standard manner..

WSDL specifies what a request message must contain and WSDL specifies what a request message must contain and what the response message will look like in unambiguous what the response message will look like in unambiguous notationnotation.. In other words, it is a contract between the XML In other words, it is a contract between the XML Web service and the client who wishes to use this service.Web service and the client who wishes to use this service.

In addition to describing message contents, WSDL defines In addition to describing message contents, WSDL defines where the service is available and what communications where the service is available and what communications protocol is used to talk to the service.protocol is used to talk to the service.

The WSDL Document StructureThe WSDL Document Structure

A WSDL document is just a simple XML A WSDL document is just a simple XML documentdocument..

It defines a web service using these major It defines a web service using these major elements:elements: port typeport type - The operations performed by the web - The operations performed by the web

service.service. message - message - The messages used by the web service.The messages used by the web service. types - types - The data types used by the web service.The data types used by the web service. bindingbinding - - The communication protocols used by The communication protocols used by

the web service.the web service.

WSDL DocumentWSDL Document<message name<message name="="GetStockPriceRequestGetStockPriceRequest"">>

<part name<part name="="stockstock" " typetype="="xsxs::stringstring"/"/>>

<<//message> message>

<message name<message name="="GetStockPriceResponseGetStockPriceResponse""> >

<part name<part name="="valuevalue" " typetype="="xsxs::stringstring"/"/>>

<<//message>message>

<portType name=“StocksRates"><portType name=“StocksRates"> <operation name=“GetStockPrice"> <operation name=“GetStockPrice"> <input message=“GetStockPriceRequest"/> <input message=“GetStockPriceRequest"/> <output message=“GetStockPriceResponse"/> <output message=“GetStockPriceResponse"/> </operation> </operation>

</portType></portType>

UDDIUDDI

UDDI stands for Universal Description, UDDI stands for Universal Description, Discovery and Integration.Discovery and Integration.

UDDI is a directory for storing information UDDI is a directory for storing information about web services , like yellow pages.about web services , like yellow pages.

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

ResourcesResources

httphttp://://msdnmsdn..microsoftmicrosoft..comcom//webserviceswebservices//understandingunderstanding//webservicebasicswebservicebasics//defaultdefault..aspxaspx

httphttp://://wwwwww..w3schoolsw3schools..comcom// httphttp://://uddiuddi..microsoftmicrosoft..comcom//DefaultDefault..aspxaspx httphttp://://wwwwww..developerdeveloper..comcom//servicesservices//articlearticle..phpphp

//21959812195981 Many more on the web…Many more on the web…

ExamplesExamples

Using a Web ServiceUsing a Web Service Creating a new Web ServiceCreating a new Web Service

Step by Step – using a web serviceStep by Step – using a web service

1.1. Inside Visual Studio .NET Choose File > Inside Visual Studio .NET Choose File > New > Project.New > Project.

2.2. Choose Visual C# Projects (or Visual Basic Choose Visual C# Projects (or Visual Basic Projects if you prefer this language).Projects if you prefer this language).

3. Choose 3. Choose ASP.NET ASP.NET Web Web Application Application as your as your templatetemplate


Inside the Location text box enter the name Inside the Location text box enter the name of your project after the prefix :of your project after the prefix :

http://localhost/YourProjectNamehttp://localhost/YourProjectName Press OK.Press OK. This makes The Internet Information This makes The Internet Information

Services installed on your computer create a Services installed on your computer create a new directory on the default path: C:\new directory on the default path: C:\Inetpub\wwwroot\FirstExampleInetpub\wwwroot\FirstExample


You can open IIS by typing compmgmt.msc \s You can open IIS by typing compmgmt.msc \s in the run command and then choosing in the run command and then choosing Services And Application > Internet Services And Application > Internet Information Services.Information Services.

Inside this node you can choose Web Sites Inside this node you can choose Web Sites node and then Default Web Site to see all the node and then Default Web Site to see all the web sites on your computer.web sites on your computer.


In the new project you opened in In the new project you opened in VS.NET Move to the Solution VS.NET Move to the Solution Explorer.Explorer.

Right Click on the References Right Click on the References folder and Choose Add Web folder and Choose Add Web References.References.

This Opens the Add Web This Opens the Add Web Reference Dialog Box.Reference Dialog Box.


Type the Web Service URL and Press Go.Type the Web Service URL and Press Go. It takes a couple of seconds to find the Web It takes a couple of seconds to find the Web

services and finally all it’s methods appear in services and finally all it’s methods appear in the list box.the list box.

The Web Reference name is shown in the The Web Reference name is shown in the Dialog Box.Dialog Box.

Press Add Reference to complete the process.Press Add Reference to complete the process.


Add a new Web Form.Add a new Web Form.


Add the following Controls to the Web FormAdd the following Controls to the Web Form


Double Click on the button and insert this code to it’s Double Click on the button and insert this code to it’s OnClick event handler.OnClick event handler.


1. Set the Web Form as the Start Page.

2. Build and Run the Program.

3. Try to use the Web Application.

Step By Step – Creating a Web ServiceStep By Step – Creating a Web Service

In this Step I will create a new Web Service In this Step I will create a new Web Service and write a Simple Program that uses it.and write a Simple Program that uses it.

The program will perform various operations The program will perform various operations on an array.on an array.

The client program will be a simple dialog The client program will be a simple dialog box that activates those opeartions.box that activates those opeartions.


Create a new Visual C# project with the name Create a new Visual C# project with the name RemoteArray. The following screen appears.RemoteArray. The following screen appears.


To see the code Press on the following hyperlink.To see the code Press on the following hyperlink.


Right Click on the References folder and Right Click on the References folder and choose add Reference.choose add Reference.

Insert the System.Windows.Forms.dll option Insert the System.Windows.Forms.dll option in to this folder.in to this folder.


Insert the following code to the .asmx file you’ve Insert the following code to the .asmx file you’ve created.created.


Press Ctrl +F5 to Run the Web service.Press Ctrl +F5 to Run the Web service.

Step By Step – Using Remote ArrayStep By Step – Using Remote Array

Add a new project to RemoteArray SolutionAdd a new project to RemoteArray Solution


Choose Windows Application from the Choose Windows Application from the templates.templates.

Add a web reference for the Remote Array Add a web reference for the Remote Array Web Service.Web Service.

Remember that it’s inside an asmx file.Remember that it’s inside an asmx file.


Add the following elements to the FormAdd the following elements to the Form


Create a private RemoteArray object and a private int Create a private RemoteArray object and a private int array object to the Form.array object to the Form.

Insert this code after the Initialize component part.Insert this code after the Initialize component part.


Insert the following code to controls handlerInsert the following code to controls handler


Set the Windows Application project as the Startup Set the Windows Application project as the Startup


Compile and run the application.Compile and run the application. This is an example that an XML Web This is an example that an XML Web

application can be used over Windows and not application can be used over Windows and not only with ASP.NETonly with ASP.NET

Introduction to Web ServicesIntroduction to Web Services

The EndThe End

Introduction to Web Services Yossi Amir Itzik Kasovitch.

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