Web Services with .Net :Web Services with .Net Presented by Amrik Goswami


Overview :Overview What is a Web Service Web Service Design Principals Exploring the ‘Façade’ pattern Creating a Web Service Attributes Returning simple and complex objects Soap Headers and Extensions Consuming a Web Service IAsyncResult Security Deploying Web Services


What is a Web Service :What is a Web Service Hype, mainly generated by marketing people…


What is a Web Service… Really!! :What is a Web Service… Really!! The execution of code on a remote machine The idea has been around for a long time!!! Remote Procedure Call (RPC) Distributed Component Object Model (DCOM) Enterprise Java Bean (EJB) WinSock (create your own protocol)


What is a Web Service cont… :What is a Web Service cont… XML is the primary means of communication, called ‘SOAP’ Usually over port 80 (HTTP), but can use any TCP port Serializes all method calls into SOAP Returns serialized objects in a SOAP format


What is a Web Service cont… :What is a Web Service cont… Pros Portable across platforms IBM, Microsoft, BEA, Sun and the WC3 support it Cons Slower than most traditional RPC methods because SOAP is VERY longwinded Still immature and undergoing change (BE WARNED)


Web Service Design Principals :Web Service Design Principals Different to most popular RPC Everything is ‘SingleCall’ Not Object Orientated (OO) ‘Stateless’ No properties (you can but…don’t) Limited OO, the more OO the slower it will be One common pattern is the ‘Façade’


Exploring the Façade pattern :Exploring the Façade pattern Think of an a Car steering wheel Hides complexity behind a well defined interface Ideal for Web Services


Creating a Web Service :Creating a Web Service Create a new ASP.Net Web Service project You get an .asmx and an .asmx.cs using System.Web.Services; Derive your class from WebService Add methods to your class and mark them with [WebMethod()]


Creating a Web Service :Creating a Web Service DEMO basicws.asmx


WebService Attribuites :WebService Attribuites Description – Provides a nice description Name – Used for ‘Aliasing’ Namespace – Effects the WSDL output Defaults to http://tempuri.org/ You should change this when developing your WebService and DEFINITELY before deploying it


WebMethod Attribuites :WebMethod Attribuites Description – Provides a nice description MessageName – Used for ‘Aliasing’ methods with same name but different signatures BufferResponse – Speeds up responses CacheDuration – Less load on resources TransactionOption – Enterprise transactions EnableSession – Allow you to read the IIS Session object from the Web Service


WebMethod Attributes :WebMethod Attributes DEMO Basicws.asmx


Returning Simple Types :Returning Simple Types Simple to return ‘simple’ types [WebMethod()] public int DoSomething(){ return 1; } Returns a simple Xml response 1


Sidebar… :Sidebar… Compatibility… using System.Web.Services.Protocols; [SoapRpcMethod()] [WebMethod()] public int DoSomething(){ return 1; } Returns a different style of Xml


Simple Types and SoapRpcMethod :Simple Types and SoapRpcMethod DEMO Basicws.asmx


Returning Simple Objects :Returning Simple Objects Same as simple types Properties… Need to be read/write Constructors… Need to have constructor with NO parameters Methods cannot be serialized


Returning Complex Objects :Returning Complex Objects using System.Web.Services.Protocols; To return a proxy of a custom type: [XmlIncude(type)] To customise the ‘Body’: [XmlAttribute()] [XmlElement(elementname)]


Returning Simple and Complex objects :Returning Simple and Complex objects DEMO Complex.asmx


Soap Headers :Soap Headers Allows you to pass extra information/class to WebMethods using System.Web.Services.Protocols; Derive a class from SoapHeader Create a public object of the class you want to pass within the WebService


Soap Headers :Soap Headers Add the [SoapHeader(“ClassInstance”)] attribute to the WebMethod Create an instance of the class Set the InstanceClassValue property of the WebService Call the WebMethod and get a handle on the SoapHeader


Soap Headers :Soap Headers DEMO Headers.asmx


Soap Extensions :Soap Extensions Allows you to inspect Soap and different stages You can modify the Soap Encryption Compression Logging Derive from SoapExtension Use ChainStream to get a writable stream Use SoapMessageStage in the ProcessMessage method to process the message Implement the other required methods


Soap Extensions :Soap Extensions ProcessMessage has several SoapMessageStages: BeforeSerialize – intercept before serialized BeforeDeserialize – intercept messages before they are deserialized * AfterSerialize – intercept messages after they are serialized * AfterDeserialize – intercept before processed


Soap Extension :Soap Extension DEMO


Consuming Web Services :Consuming Web Services ‘Add Web Reference’ to your project ASP.Net, Windows Forms, Console, Windows Service, COM+ Any .NET project… Using WSDL.exe Wsdl /out:proxyclassfilename.cs mywsdlfile.wsdl Add generated proxy file to project then call methods Creating Proxy objects


Consuming Web Services :Consuming Web Services Call WebMethods just like ordinary methods ‘Update Web References’ when you add new stuff Regenerate proxy with WSDL.exe when you add new stuff, re-add the proxy class file


Consuming and WSDL :Consuming and WSDL DEMO


IAsyncResult (Callback method) :IAsyncResult (Callback method) Create an AsyncCallback Create a method that takes an IAsyncResult parameter Call the Begin… method and pass in any parameters, the AsyncCallback and the proxy


IAsyncResult (WaitOne method) :IAsyncResult (WaitOne method) Call the Begin… method and pass in any parameters, null as the Callback and null as the proxy Call WaitOne until IsCompleted is true


Async Calls :Async Calls DEMO


Security :Security Often security is an afterthought It IS IMPORTANT !! Credentials are NOT passed to WebServices even when you use impersonation Web.Config file is STILL important to WebServices You must ‘Enable’ it


Security :Security Credentials (Point-To-Point) Set the Credentials property You can also create credentials at run-time Based on Windows accounts Tickets (Application) Needs to be passed with every method call Custom, roll your own Soap Header based


Security :Security WS-Security (End-To-End) Emerging standard Can use Custom, Binary, Kerberos Tokens X.509 digital certificates Soap Header based Need WS Enhancements V1.0 (V2.0 in preview) Soap Extensions Can provide some basic message level encryption


Security :Security Passing Credentials Proxy.Credentials = System.Net.CredentialCache.DefaultCredentials; You can also create your own credentials and attach them to the request Watch out for WS-Security…. things are changing…


Security :Security DEMO


Deployment :Deployment When you ‘Add a Web Reference’ the URL property is HARD CODED WSDL contains the URL from the site it was generated To the rescue… the proxy has a URL property that you can set to point to the WebService You can implement Load Balancing… Remember the MSI… Create Web Setup projects to deploy your WebService


Deployment :Deployment DEMO


Summary :Summary Beware of the HYPE!! Remember to design differently Use Attributes to customise your Xml As a minimum, set the Description and the Namespace Think (consider…) Async Be secure!! Use the deployment tools you have in the box


References :References Patterns and Practices: Building Secure ASP.NET Applications: Authentication, Authorization, and Secure Communication MSDN: Search for ‘Web Services’ MCAD/MCSD Self Paced Training: Developing XML Web Services and Server Components with Visual Basic.NET and Visual C#.NET, Microsoft Press