Transcript Week 5- ppt - Monash University

.NET XML Web Services
Monash University
Semester 1, March 2006
www.monash.edu.au
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
Broker
Search
Publish
Consumer
Provider
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 internetbased protocols.”
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Distributed Programming Model
Server
Client
Web Services Description Language
(WSDL)
Client Proxy
Server Stub
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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Web Services and Firewalls
Consumer
U
RMI
Service
Port 80
Web
Service
U
DCOM
Service
Firewall
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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
UDDI
Broker
Search
Publish
WSDL
Applications
Consumer
Provider
Bind/Invoke
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Business Applications n-tier
Communication
Web Service
Web Service
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ASP.NET XML Web Services
• Must use an .ASMX file to create or generate
a web interface
• An ASMX file can contain code or point to a
DLL using Code behind
• Must inherit from
System.Web.Services.WebService or
implement
System.Web.Services.WebService as 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
<%@ WebService Language="C#" Class=“MonashIT.HelloWorld,MonashITLibrary" %>
• Implementation
– .CS file
public class HelloWorld: System.Web.Services.WebService
{
[WebMethod]
public string Hello ()
{
return “Hello World”;
}
}
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Web Method
• Description - a property which makes a
description available to a WSDL file
• MessageName - the method name used
when calling a Web Method
• Enable Session - defines whether a session
state is enabled
• TransactionOption - indicates transaction
support
• CacheDuration – defines the length of time
the method 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#
wsdl http://localhost/hello/HelloWorld.asmx?wsdl
• Visual Studio .NET automates this process by creating
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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)]
public string YourName(string name)
{
if(Session["Name"] == null)
Session.Add("Name", name);
return Session["Name"].ToString();
}
[WebMethod(EnableSession=true)]
public string GetName()
{
if(Session["Name"] == null)
return "no name recorded";
else
return Session["Name"].ToString();
}
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Caching
Key
• Uses the ASP.NET Caching Model
• Improves the performance of application by
caching messages
Normal
Cached
Complier
Output Cache
Parser
Memory
Assembly
Cache
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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
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