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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
