Www.monash.edu.au.NET XML Web Services Monash University Semester 1, March 2006

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.NET XML Web Services

Monash University

Semester 1, March 2006

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Overview

• Current Business Models• What are XML Web Services and why use

them• How web services are developed

using .NET• Extensions to Web Services using .NET

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Business Applications 3-tier

• Business applications must separate software into 3 tiers

• Separate the business process from the user interface and data layers

User Interface

Business Objects

Data Layers

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Extend your business

• With 3-tier architecture, you restrict your business to your applications

• With global economy, you want different global companies to use your software

• Need to provide another tier to your business process

• Service Oriented Architecture is what can be used to expose your business to the software world

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Service Oriented Architecture

ProviderConsumer

Broker

PublishSearch

Bind/Invoke

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What are XML Web Services

• W3C Definition– “… software application identified by a URI,

whose interfaces and binding are capable of being defined, described and discovered by XML artefacts and supports direct interactions with other software applications using XML based messages via internet-based protocols.”

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Distributed Programming Model

Client Server

Web Services Description Language (WSDL)

Server StubClient Proxy

SOAP, XML-RPC

Transport (HTTP, FTP, IIOP etc.)

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Why XML Web Services

• Supports n-tier Application Architecture (Façade Pattern should be used)

• Provide a web interface to you current business infrastructure

• Use web protocols and standards to communicate and transfer information

• Can be used to communicate through firewalls that block other Distributed Programming models

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WebService

RMIService

DCOMService

Consumer

Firewall

Port 80

Web Services and Firewalls

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Web Services Standards and Protocols

• Open Web Protocols– HTTP, XML, SOAP etc.

• Web Services Contracts/Description– WSDL

• Advertising and Discovery– UDDI, Disco

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Service Oriented Architecture

ProviderConsumer

Broker

PublishSearch

Bind/Invoke

Applications

UDDI

WSDL

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Business Applications n-tier

Web Service Web Service

Communication

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ASP.NET XML Web Services

• Must use an .ASMX file to create or generate a Must use an .ASMX file to create or generate a web interfaceweb interface

• An ASMX file can contain code or point to a An ASMX file can contain code or point to a DLL using Code behind DLL using Code behind

• Must inherit from Must inherit from System.Web.Services.WebService or System.Web.Services.WebService or implement System.Web.Services.WebService implement System.Web.Services.WebService as a custom attribute of your classas a custom attribute of your class

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Demonstration HelloWorldWS

• Basic Hello World in .NET

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Create a Web Service in ASP.NET

• Declaring Web Services– .ASMX file

• Implementation– .CS file

public class HelloWorld: System.Web.Services.WebServiceSystem.Web.Services.WebService{{

[WebMethod][WebMethod]public string Hello ()public string Hello (){{

return “Hello World”;return “Hello World”;}}

}}

<%@ WebService Language="C#" Class=“MonashIT.HelloWorld,MonashITLibrary" %>

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Web Method

• Description - a property which makes a Description - a property which makes a description available to a WSDL filedescription available to a WSDL file

• MessageName - the method name used when MessageName - the method name used when calling a Web Method calling a Web Method

• Enable Session - defines whether a session Enable Session - defines whether a session state is enabledstate is enabled

• TransactionOption - indicates transaction TransactionOption - indicates transaction supportsupport

• CacheDuration – defines the length of time the CacheDuration – defines the length of time the method invocation should be cached formethod invocation should be cached for

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Stateless and Statefull services

• Stateless means a web service losses its state

• Web services are normally stateless• Usually provide access to state information

such as databases and XML files• .NET Web services are stateless by default• More will be covered in Module 8

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Publishing Web Services

• Files– Web.Config and Global.asax file

– Assemblies and .asmx files

• IIS structure– Must create a virtual directory

– Must ensure that the web service has appropriate permissions to access and modify resources

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Consuming Web Services

• Accessing Web Services from IE– Demonstration

• Proxy class• WSDL tool

– Generate source file. Need to compile– Default is in C#

• Visual Studio .NET automates this process by creating

wsdl http://localhost/hello/HelloWorld.asmx?wsdl

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Demonstration

• A stock service demonstration

http://localhost/StockTradingService/StockService.asmx

localhost/WapStockClient/Stocks.aspx

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WS State Management

• Statement management objects– Application

– Session

• EnabledSession property in WebMethod attribute– To enable Session object.

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State Management

• Web Services are stateless• Use ASP.NET session state mechanism

– Restricted to a logical application

– Context in which a user communicates to a server

– Functionality> Request identification and classification> Store data across multiple requests> Session events> Release of session data

– .NET State Server Process

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State Management

• Each request of a Web Service its class instance is instantiated and thrown away when it is no longer used– i.e. each time you call a method the class

variable values are not available be the web service has be re-instantiated

• If data is required to be used between different requests, the ASP.NET built-in session state mechanisms must be used

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State Management (cont…)

• Web services have access to the same state management options as other ASP.NET applications such as the Session and Application objects and cookies

• Data stored in the Session object is available only when the EnableSession property of the WebMethod attribute is set to true. Access to the Application object is automatic however

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State Management (e.g.)

• Declaring a Web service method, with the EnableSession property equal to WebMethod attribute to true.

[WebMethod(EnableSession=true)][WebMethod(EnableSession=true)]public string YourName(string name)public string YourName(string name){{ if(Session["Name"] == null)if(Session["Name"] == null) Session.Add("Name", name);Session.Add("Name", name);

return Session["Name"].ToString();return Session["Name"].ToString();}}

[WebMethod(EnableSession=true)][WebMethod(EnableSession=true)]public string YourName(string name)public string YourName(string name){{ if(Session["Name"] == null)if(Session["Name"] == null) Session.Add("Name", name);Session.Add("Name", name);

return Session["Name"].ToString();return Session["Name"].ToString();}}

[WebMethod(EnableSession=true)][WebMethod(EnableSession=true)]public string GetName()public string GetName(){{ if(Session["Name"] == null)if(Session["Name"] == null) return "no name recorded";return "no name recorded"; elseelse return Session["Name"].ToString();return Session["Name"].ToString();}}

[WebMethod(EnableSession=true)][WebMethod(EnableSession=true)]public string GetName()public string GetName(){{ if(Session["Name"] == null)if(Session["Name"] == null) return "no name recorded";return "no name recorded"; elseelse return Session["Name"].ToString();return Session["Name"].ToString();}}

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Caching

• Uses the ASP.NET Caching Model• Improves the performance of application by

caching messages

Parser

Assembly CacheMemory

ComplierOutput C

ache

Key

Normal

Cached

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Web Service Execution Model

• Synchronous– Like any other call to class methods

• Asynchronous– Split the method into two code blocks

> BeginMethodName> EndMethodName

– CLR determines if and when operation has finished

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Asynchronous invocation

• Exposed in generated proxy class– Begin and End method

• Begin method– Return IAsyncResult

– Parameters > AsyncCallback> Object

• End method– Return function return type

– First parameter is IAsyncResult

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Demonstration

• Building an application that supports asynchronous invocation

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Transaction Support in Web Services

• Same as COM+ and Microsoft Transaction Server

• Declarative Transaction• TransactionOption property in WebMethod

attribute

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Windows security

• Client application– NetworkCredential class

> Username, password, domain

– CredentialCache class

– Credentials property in proxy class

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Web Services Security

• ASP.NET Security– Windows security, IIS security

– Web.config file

• Customised SOAP-based security– SOAP Header

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SOAP Header

• Inherit from SOAPHeader class• Declare a public attribute• Apply SOAPHeader attribute to

WebMethod– MemberName property

• However, this is .NET specific

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Global XML Architecture

• GXA provides uniform way of using XML web services

• A Microsoft specific initiative to web services• Supports new extensions to web services• Implemented in .NET using Web Services

Enhancements

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Web Services Enhancements 2.0

• Provides additional Web Services capabilities• Additional WS specifications

– WS-Security

– WS-Policy

– WS-Trust

– WS-Addressing

– Etc.

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WS-Security

• By OASIS• Enhancements to

SOAP messaging• A general purpose

mechanism for secure messaging

• Support symmetric and public key technologies

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WSE 2.0 Demo

• Using Asymmetric Encryption• Using digital certificates

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Web Service Technologies

• EJB using Tomcat & Sun ONE toolkit• BEA Weblogic• IBM Web Sphere • .NET using ASP.NET and IIS• Many more available

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Communication between systems

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Conclusion

• Businesses use web services for interoperability

• .NET offers web services through ASP.NET

• ASP.NET provides caching and supports the Global XML architecture through Web Services extensions