Advanced Web Services Using Microsoft ASP.NET Malini S. Puttaiah

1
Advanced Web Services Using Microsoft ASP.NET
Malini S. Puttaiah Ranjit R. Sawant
Developer Support Engineers Microsoft
Corporation
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Topics

• Web services architecture
• Simple Web service
• Managing state in Web service
• SOAP headers
• SOAP extensions
• Formatting SOAP messages
• Security in Web services
• Calling Web services asynchronously
• Exceptions and error handling in Web services
• Transaction support
• XML Web services discovery UDDI, Disco

3
Web Services Architecture

• XML Web services protocols and standards
• XML Web services infrastructure
• XML Web services message flow

4
XML Web Services Protocols and Standards

• XML
• Simple Object Access Protocol (SOAP)
• Web Services Description Language (WSDL)
• XSD
• application/x-www-form-urlencoded

5
XML Web Services Infrastructure
Directory
1) Client attempts to locate a Web service 2)
URL to discovery document is returned
3) Client requests discovery document 4)
Discovery document is returned
Discovery
Description
5) Client requests service description 6)
Description document is returned
Wire Format
7) Client requests the web service 8) Web
service returns result response
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XML Web Services Message Flow
SOAP Request
SOAP MESSAGE
SOAP MESSAGE
Phase II DeSerialize
Phase I Serialize
Network
Web Service
Client Proxy
Phase III Serialize
Phase IV DeSerialize
SOAP MESSAGE
SOAP MESSAGE
SOAP Response
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Simple XML Webservice Declaration

• Class implementing the Web service can optionally
  derive from System.Web.Services.WebService to
  gain access to common ASP.NET objects like
  Application, Session, User, and Context
• Simple Webservice declaration

• WebService(Description"MySimpleService does
  simple Math operations",Namespace"http//myadvanc
  edwebserviceURI/")
• public class MySimpleService WebService
• WebMethod(Description"Adds 2 numbers")
• public int Add(int num1, int num2)
• return num1num2
• ........

8
WebMethod Attributes Important Properties

• BufferResponse
• CacheDuration
• Description
• EnableSession
• MessageName
• TransactionOption

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Managing State in XML Web Services

• State data can be saved by using the ASP.NET
  Session and Application objects
• Data stored in the Session object is available
  only when the EnableSession property of the
  WebMethod attribute is set to TRUE
• Storing state data in Application object
• Applicationstrapplication" This string can
  be accessed by any application
• Storing state data in Session object
• Sessionstrsession" This string can be
  accessed in this session only

10
Session State Management

• Session state for each client is identified by
  the session ID, which is stored as a cookie on
  the client
• Session ID cookies are sent to the client when a
  call is made to the method that has the
  EnableSession property of the WebMethod
  attribute set to TRUE
• Every subsequent call from the client to the
  service has this cookie accompanying it

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Session State Management (2)

• Client should be cookie enabled
• localhost.ManageState objmanagestate new
  localhost.ManageState()
• System.Net.CookieContainer cc new
  System.Net.CookieContainer()
• objmanagestate.CookieContainer cc
• objmanagestate.SomemethodCall()
• Example
• //server
• WebMethod(Description"SetSomeProperty",EnableSes
  siontrue)
• public void SetSomeProperty(string str)
• Session"myProperty" str
• WebMethod(Description"GetSomeProperty",EnableSe
  ssiontrue)
• public string GetSomeProperty()
• return (string)Session"myProperty"
• //client

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SOAP Messages for Session State Enabled Method

• SetSomeProperty REQUEST
• POST /SimpleMathservice/Math.asmx HTTP/1.1
• User-Agent Mozilla/4.0 (compatible MSIE 6.0 MS
  Web Services Client Protocol 1.0.3705.0)
• Content-Type text/xml charsetutf-8
• SOAPAction "http//myadvancedwebserviceURI/SetSom
  eProperty"
• Content-Length 338
• Expect 100-continue
• Connection Keep-Alive
• Host localhost
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope/"
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-insta
  nce"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltsoapBodygt
• ltSetSomeProperty xmlns"http//myadvancedwebserv
  iceURI/"gt
• ltstrgtSomePropertyValuesentfromclientlt/strgt
• lt/SetSomePropertygt
• lt/soapBodygt

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SOAP Messages for Session State Enabled Method (2)

• SetSomeProperty RESPONSE
• HTTP/1.1 100 Continue
• Server Microsoft-IIS/5.0
• Date Sat, 09 Mar 2002 173202 GMT
• HTTP/1.1 200 OK
• Server Microsoft-IIS/5.0
• Date Sat, 09 Mar 2002 173202 GMT
• Set-Cookie ASP.NET_SessionIduuvatj55k2bbpsig2fho
  icaw path/
• Cache-Control private, max-age0
• Content-Type text/xml charsetutf-8
• Content-Length 313
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope/"
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
  ce"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltsoapBodygt
• ltSetSomePropertyResponse xmlns"http//myadvancedw
  ebserviceURI/" /gt
• lt/soapBodygt

14
SOAP Headers

• Represents out-of-bounds data between the
  communicating parties
• The Header can be can be sent without the
  sender/receiver having prior knowledge
• The Header element is encoded as the first
  immediate child element of the SOAP Envelope XML
  element
• The SOAP mustUnderstand attribute and SOAP Actor
  attribute may be used with the Header element to
  indicate how to process the Header entry and by
  whom

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Sample SOAP Header

• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope
• xmlnssoap"http//schemas.xmlsoap.org/soap/envelo
  pe/
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
  ce
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltsoapHeadergt
• ltMyauthenticationHeader xmlns"http//tempuri.or
  g/"gt ltUsernamegtadminlt/Usernamegt
  ltPasswordgtpasswordlt/Passwordgt
• lt/MyauthenticationHeadergt
• lt/soapHeadergt
• ltsoapBodygt
• ltMyWebMethod xmlns"http//tempuri.org/"/gt
• lt/soapBodygt
• lt/soapEnvelopegt

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SOAP Header Implementation Server

• //Define a SOAP header by deriving from the
  SoapHeader
• public class MyauthenticationHeader SoapHeader
  
• public string Username
• public string Password
• //Web service
• public class Service1 System.Web.Services.We
  bService
• public MyauthenticationHeader objAuthHeader
• . . . .
• SoapHeader("objAuthHeader")
• WebMethod
• public string MyWebMethod()
• //access the Header values here
• if( objAuthHeader.UserName
  admin). . .

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SOAP Header Implementation Client

• void CallWebServiceMethod()
• //instantiate the Header object in the client
• localhost.MyauthenticationHeader objauthheader
  
• new localhost.Myauthenticatio
  nHeader()
• //Populate the class members
• objauthheader.Username "admin"
• objauthheader.Password "password"
• //instantiate the service object
• localhost.Service1 objservice new
  localhost.Service1()
• //Equate the proxy class member to the header
  object
• objservice.MyauthenticationHeaderValue
  objauthheader
• //Call the method marked with SOAPHeader
  attribute on
• //the webservice
• objservice.MyWebMethod()

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SoapHeader Attributes Required

• Setting the Required property of the SoapHeader
  attribute to FALSE makes the SOAP header optional
• //Server
• SoapHeader("objTransactionHeader",Requiredfalse)
  
• WebMethod
• public string MyWebMethod2()
• if(objTransactionHeader ! null)
• objTransactionHeader.TransactionID 12345678
• return "Inside MyWebMethod2"
• //Client
• localhost.Service1 objservice new
  localhost.Service1()
• //you do not have to initialize the Header before
  calling
• // the webmethod
• objservice.MyWebMethod2()

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SoapHeader Attributes SoapHeaderDirection

• SoapHeaderDirection represents the SOAP Actor
  attribute
• In, Out, or InOut
• //Server
• WebMethod
• SoapHeader("myOutHeader,DirectionSoapHeaderDire
  ction.Out)
• public void MyOutHeaderMethod()
• // Return the client's authenticated name.
  myOutHeader.Username someusername
• //Client
• localhost.Service1 objservice new
  localhost.Service1()
• objservice.MyOutHeaderMethod()
• //Displays someusername
• MessageBox.Show( objservice.myOutHeaderValue.UserN
  ame)

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Handling Unknown SOAP Headers

• Mustunderstand and Didunderstand properties
• Client calling the method
• localhost.someheader1 objsomeheader
• new localhost.someheader1
  ()
• objservice.Mysomeheader1Value objsomeheader
• objservice.Mysomeheader1Value.MustUnderstand
  true
• objservice.MyWebMethod3()
• Client define and instantiate header in proxy
  class
• public class someheader1 SoapHeader
• public string strname
• public someheader1 Mysomeheader1Value
• Client modify method attributes in proxy class
• System.Web.Services.Protocols.SoapHeaderAttribute
  ("Mysomeheader1Value",Requiredfalse)
• public string MyWebMethod3().

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Handling Unknown SOAP Headers (2)

• Server defining unknown headers collection
• public SoapUnknownHeader unknownHeaders
• Server method implementation
• SoapHeader("unknownHeaders", Required false)
• WebMethod
• public string MyWebMethod3()
• string str ""
• foreach (SoapUnknownHeader header in
  unknownHeaders)
• if (header.Element.Name "someheader1")
• header.DidUnderstand true
• str "understood the header"
• else
• header.DidUnderstand false
• str "Did not understand the header"

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SOAP Extensions

• SOAP extensions allow developers to augment the
  functionality of an XML Web service by altering
  the SOAP messages sent to and from an XML Web
  service or an XML Web service client
• A SOAP extension can be injected into the message
  infrastructure to inspect or modify the SOAP
  messages before and after the serialize and
  deserialize phases
• Phases defined by SoapMessageStage enumeration
  AfterSerialize , BeforeDeserialize

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Implementing SOAP Extensions

• Derive a class from SoapExtension
• Save a reference to the stream representing
  future SOAP messages
• Initialize SOAP extensionspecific data
• Process the SOAP messages during the pertinent
  SoapMessageStage or stages
• Configure the SOAP extension to run with specific
  XML Web service methods

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SoapExtension Class

• The class deriving from SoapExtension is the
  class that performs the functionality of the SOAP
  extension
• Members
• ChainStream When overridden in a derived class,
  allows a SOAP extension access to the memory
  buffer containing the SOAP request or response.
• GetInitializer Overloaded. When overridden in a
  derived class, allows a SOAP extension to
  initialize data specific to an XML Web service
  method at a one time performance cost.

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SoapExtension Class (2)

• Members (cont)
• Initialize When overridden in a derived class,
  allows a SOAP extension to initialize itself
  using the data cached in the GetInitializer
  method.
• ProcessMessage When overridden in a derived
  class, allows a SOAP extension to receive a
  SoapMessage to process at each SoapMessageStage.

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SoapExtension Implementation

• public class TraceExtension SoapExtension
• Stream oldStream Stream newStream string
  filename
• .
• public override void ProcessMessage(SoapMessage
  message) switch (message.Stage)
• case SoapMessageStage.BeforeSerialize break
  
• case SoapMessageStage.AfterSerialize
• WriteOutput( message )
• break
• case SoapMessageStage.BeforeDeserialize
• WriteInput( message )
• break
• case SoapMessageStage.AfterDeserialize
  break
• default throw new Exception("invalid
  stage")
• public override Stream ChainStream( Stream stream
  ) oldStream stream newStream new
  MemoryStream() return newStream

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Extensions Sequence of Operations for Request

• REQUEST client side
• A client invokes a method on the proxy class.
• A new instance of the SOAP extension is created
  on the client.
• GetInitializer method is invoked on the SOAP
  extension running on the client.
• The Initialize method is invoked.
• The ChainStream method is invoked.

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Extensions Sequence of Operations for Request (2)

• REQUEST client side (cont)
• The ProcessMessage method is invoked with the
  SoapMessageStage set to BeforeSerialize.
• ASP.NET on the client computer serializes the
  arguments of the XML Web service method into XML.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to AfterSerialize.
• ASP.NET on the client computer sends the SOAP
  message over the network to the Web server
  hosting the XML Web service.

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Extensions Sequence of Operations for Request (3)

• REQUEST server side
• ASP.NET on the Web server receives the SOAP
  message.
• A new instance of the SOAP extension is created
  on the Web server.
• The GetInitializer method is invoked on the SOAP
  extension running on the server.
• The Initialize method is invoked.
• The ChainStream method is invoked.

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Extensions Sequence of Operations for Request (4)

• The ProcessMessage method is invoked with the
  SoapMessageStage set to BeforeDeserialize.
• ASP.NET deserializes the arguments within the
  XML.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to AfterDeserialize.
• ASP.NET creates a new instance of the class
  implementing the XML Web service and invokes the
  XML Web service method, passing in the
  deserialized arguments. This object resides on
  the same computer as the Web server.
• The XML Web service method executes its code,
  eventually setting the return value and any out
  parameters.

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Extensions Sequence of Operations for Response

• Server side
• The XML Web service method executes its code,
  eventually setting the return value and any out
  parameters.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to BeforeSerialize.
• ASP.NET on the Web server serializes the return
  value and out parameters into XML.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to AfterSerialize.
• ASP.NET sends the SOAP response message over the
  network back to the XML Web service client.

32
Extensions Sequence of Operations for Response
(2)

• Client side
• ASP.NET on the client computer receives the SOAP
  message.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to BeforeDeserialize.
• ASP.NET deserializes the XML into the return
  value and any out parameters.
• The ProcessMessage method is invoked with the
  SoapMessageStage set to AfterDeserialize.
• ASP.NET passes the return value and any out
  parameters to the instance of the proxy class.
• The client receives the return value and any out
  parameters.

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Configuring Soap Extensions

• Config file Applies to all methods in the
  service
• ltwebServicesgt
• ltsoapExtensionTypesgt
• ltadd type"SoapTraceExtension.TraceExtension,
  SoapTraceExtension" /gt
• lt/soapExtensionTypesgt
• lt/webServicesgt
• Use a custom attribute
• Derive a class from SoapExtensionAttribute
• public class TraceExtensionAttribute
• SoapExtensionAttribute
• Apply the attribute to Web method
• WebMethod
• TraceExtensionAttribute
• public string HelloWorld() . . .

34
Formatting SOAP Messages

• SOAP specification does not strictly outline the
  formatting of the XML message.
• SOAP specification defines message formatting in
  two sections
• Section 5 How are the parameters within the SOAP
  body encoded?
• Parameters are either ENCODED or LITERAL
• Section 7 How is the entire SOAP BODY formatted?
• SOAP BODY can be either in RPC or DOCUMENT style
• ASP.NET provides an attribute-based mechanism for
  controlling the format of the XML in the SOAP
  message. It can be applied to the entire message
  or at the individual element in the message.

35
Formatting Styles Supported by ASP.NET Web
Services
36
Document Literal

• Method definition
• SoapDocumentMethod( UseSoapBindingUse.Literal)
• public Stockinfo GetStockInfoDocumentLiteral(
• string companyname,string
  stockExchangename)
• Response message
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope/"
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-in
  stance"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltsoapBodygt
• ltGetStockInfoDocumentLiteralResponse
• xmlns"http//tempuri.org
  /"gt
• ltGetStockInfoDocumentLiteralResultgt
• ltstocknamegtABCD123lt/stocknamegt
• ltlasttradedpricegt23.5lt/lasttradedpri
  cegt
• ltvolumegt3454353lt/volumegt

37
Document Encoded

• Method definition
• SoapDocumentMethod( UseSoapBindingUse.Encoded)
• public Stockinfo GetStockInfoDocumentEncoded (
• string companyname,string
  stockExchangename)
• Response message
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoap Envelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope" xmlnssoapenc"http//sc
  hemas.xmlsoap.org/soap/encoding/"
  xmlnstns"http//tempuri.org/"
  xmlnstypes"http//tempuri.org/encodedTypes"
  xmlnsxsi"http//www.w3.org/2001/XMLSc
  hema-instance" xmlnsxsd"http//ww
  w.w3.org/2001/XMLSchema"gt
• ltsoapBody soapencodingStyle"http//schemas.xmls
  oap.org/soap/encoding/"gt
• lttypesGetStockInfoDocumentEncodedResponsegt
• ltGetStockInfoDocumentEncodedResult
  href"id1" /gt
• lt/typesGetStockInfoDocumentEncodedResponsegt
• lttypesStockinfo id"id1" xsitype"typesStoc
  kinfo"gt
• ltstockname xsitype"xsdstring"gtABCD123lt/sto
  cknamegt
• ltlasttradedprice xsitype"xsddouble"gt23.5lt/
  lasttradedpricegt
• ltvolume xsitype"xsdint"gt3454353lt/volumegt
• lt/typesStockinfogt

38
RPC Encoded

• Method definition
• SoapRpcMethod()
• public Stockinfo GetStockInfoRPCEncoded (
• string companyname,string
  stockExchangename)
• Response message
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope"
• xmlnssoapenc"http//schemas.xmlsoap.org/soa
  p/encoding/"
• xmlnstns"http//tempuri.org/"
• xmlnstypes"http//tempuri.org/encodedTypes"
  
• xmlnsxsi"http//www.w3.org/2001/XMLSchema-i
  nstance"
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
  
• ltsoapBody soapencodingStyle"http//schemas.xm
  lsoap.org/soap/encoding/"gt
• lttnsGetStockInfoRPCEncodedResponsegt
• ltGetStockInfoRPCEncodedResult href"id1" /gt
• lt/tnsGetStockInfoRPCEncodedResponsegt

39
Parameter Wrapping/Unwrapping

• Wrapping is the default for document-literal
• UnWrapping
• Method definition
• SoapDocumentMethod(UseSoapBindingUse.Literal,
• ParameterStyleSoapParameterStyle.Bare )
• public Stockinfo GetStockInfoBareParam(
• string companyname,string
  stockExchangename). .
• SOAP message
• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope
• xmlnssoap"http//schemas.xmlsoap.org/soap/envelo
  pe/"
• xmlnsxsi "http//www.w3.org/2001/XMLSchema-insta
  nce
• xmlnsxsd"http//www.w3.org/2001/XMLSchema"gt
• ltsoapBodygt
• ltcompanyname xmlns"http//tempuri.org/"gt
• ABCD123
• lt/companynamegt
• ltstockExchangename xmlns"http//tempuri.org/"gt

40
Security in ASP.NET Web Services

• Authentication
• Windows-based
• Basic
• Digest
• Windows integrated-NTLM or Kerberos
• Client certificates
• Custom SOAP headers
• Authorization using ASP.NET configuration
• Impersonation using ASP.NET configuration
• Data encryption
• SSL
• Custom SOAP extension

41
Authentication Windows-Based

• Basic authentication
• localhost.Service1 objlocalhost new
  localhost.Service1()
• // Create a new instance of CredentialCache.
• CredentialCache credentialCache new
  CredentialCache()
• //Create a new instance of NetworkCredential
  using the client
• NetworkCredential credentials
  new NetworkCredential("Administrator","Password1")
  
• // Add the NetworkCredential to the
  CredentialCache.
• credentialCache.Add(new Uri(objlocalhost.Url),"Bas
  ic",
• 
  credentials)
• // Add the CredentialCache to the proxy class
  credentials.
• objlocalhost.Credentials credentialCache
• // Call the method on the proxy class.
• objlocalhost.HelloWorld()

42
Authentication Windows-Based (2)

• NTLM authentication
• localhost.Service1 objlocalhost new
  localhost.Service1()
• // Create a new instance of CredentialCache.
• CredentialCache credentialCache new
  CredentialCache()
• //Create a new instance of NetworkCredential
  using the client
• NetworkCredential credentials
  new NetworkCredential("Administrator","Password1")
  
• // Add the NetworkCredential to the
  CredentialCache.
• credentialCache.Add(new Uri(objlocalhost.Url),NTL
  M",
• 
  credentials)
• // Add the CredentialCache to the proxy class
  credentials.
• objlocalhost.Credentials credentialCache
• // Call the method on the proxy class.
• objlocalhost.HelloWorld()

43
Authentication Client Certificates

• localhost.Service1 objlocalhost new
  localhost.Service1()
• // Create a new instance of CredentialCache.
• CredentialCache credentialCache new
  CredentialCache()
• // Create a new instance of NetworkCredential
  using the client
• NetworkCredential credentials
  new NetworkCredential("Administrator","Password1")
  
• // Add the NetworkCredential to the
  CredentialCache.
• credentialCache.Add(new Uri(objlocalhost.Url),
  "Basic",
• 
  credentials)
• // Add the CredentialCache to the proxy class
  credentials.
• objlocalhost.Credentials credentialCache
• // Load the client certificate from a file.
• X509Certificate x509 X509Certificate.CreateFromC
  ertFile("C\\clicert.cer")
• // Add the client certificate to the
  ClientCertificates property
• // of the proxy class.
• objlocalhost.ClientCertificates.Add(x509)

44
Authentication Custom SOAP Headers

• Server implementation
• //Define a SOAP header by deriving from the
  SoapHeader
• public class MyauthenticationHeader SoapHeader
  
• public string Username
• public string Password
• //Web service
• public class Service1 System.Web.Services.We
  bService
• public MyauthenticationHeader objAuthHeader
• . . . .
• SoapHeader("objAuthHeader")
• WebMethod
• public string MyWebMethod()
• //access the Header values here
• if( objAuthHeader.UserName
  admin). . .

45
Authentication Custom SOAP Headers (2)

• Client implementation
• //instantiate the Header object in the client
• localhost.MyauthenticationHeader objauthheader
  
• new localhost.Myauthenticatio
  nHeader()
• //Populate the class members
• objauthheader.Username "admin"
• objauthheader.Password "password"
• //instantiate the service object
• localhost.Service1 objservice new
  localhost.Service1()
• //Equate the proxy class member to the header
  object
• objservice.MyauthenticationHeaderValue
  objauthheader
• //Call the method marked with SOAPHeader
  attribute on
• //the webservice
• objservice.MyWebMethod()

46
Authorization

• ASP.NET authorization types
• File authorization NTFS-based on ACL
• URL authorization maps users and roles to
  pieces of the URI namespace
• Configure authorization in ASP.NET configuration
  files
• ltauthorizationgt ltallow verb"GET" users"" /gt
• ltallow verb"POST" users"Administrator" /gt
• ltallow verb"POST" users"Kim" /gt
• ltdeny verb"POST" users"" /gt
• lt/authorizationgt

47
Impersonation

• Configure Web services impersonation in the
  ASP.NET configuration files
• ltidentity impersonate"true" userNameuser1
  password"pass"/gt

48
Encryption

• Secure sockets layer
• Client proxys URL property
• https//localhost/SecureWebservice/Service1.asmx
• Custom encryption
• Use SOAP extension
• Encrypt in AfterSerialize
• Decrypt in BeforeDeSerialize

49
Invoking Web Services Asynchronously

• Synchronous versus asynchronous invocations
• Asynchronous design patterns in .NET
• Invoking Web services asynchronously

50
Synchronous Calls

• Synchronous calls block a process until operation
  is complete

Client
Server
1
Calling Code
Object being called
Client calls object
and call is blocked
Method completes
3
2
Next line of execution
51
Asynchronous Calls

• An asynchronous operation will not block the
  calling thread
• The calling application must then discover
  completion of the call by polling, by software
  interrupt, or by waiting explicitly for
  completion later

Client
Server
1
Calling Code
Object being called
Client calls object
Call returns
2
Next line of execution
3
Sink Object
Method completes
52
Asynchronous Programming in .NET

• Client code decides if a call has to be
  asynchronous
• Called object does not need to do additional
  programming to support asynchronous behavior
• Called object can also choose to explicitly
  support asynchronous behavior if it wants to
  implement more efficiently than the general
  architecture

53
Ways of Calling Asynchronously

• Use callbacks
• Supply the callback delegate when beginning
  asynchronous calls
• Wait handle
• Wait on IAsyncResult WaitOne, WaitAll, WaitAny
• Poll completed
• Poll the returned IAsyncResult.IsCompleted
  property for completion of calls

54
Closer Look at Proxy Class

• public int Add(int x, int y, int DelaySeconds)
• object results this.Invoke("Add",
• new object x, y, DelaySeconds)
• return ((int)(results0))
• public System.IAsyncResult BeginAdd(int x, int y,
  int DelaySeconds, System.AsyncCallback callback,
  object asyncState)
• return this.BeginInvoke("Add", new
  object x, y,
• DelaySeconds, callback,
  asyncState)
• public int EndAdd(System.IAsyncResult
  asyncResult)
• object results this.EndInvoke(asyncRes
  ult)
• return ((int)(results0))

55
Sample Web Service

• WebMethod
• public double Add(int x , int y, int
  DelaySeconds)
• //Create a delay to simulate a long-running
  process
• if (DelaySeconds gt 0)
• System.Threading.Thread.Sleep(DelaySeconds
  1000)
• return x y

56
Synchronous Call Client

• localhost.MathServer obj new
  localhost.MathServer()
• double result obj.Add(firstNumber,
• secNumber, DelaySecs)
• Console.WriteLine("Addition result is "
  result.ToString() )

57
Asynchronous Call Using Callback

• localhost.MathServer obj new
  localhost.MathServer()
• AsyncCallback cb new AsyncCallback(MyCallBack)
  
• IAsyncResult ar obj.BeginAdd(firstNumber,
• secNumber, delay, cb, null)
• MessageBox.Show ("Async call invoked
  successfully,
• "Async call")
• public void MyCallBack(System.IAsyncResult ar)
• localhost.MathServer obj1 (localhost.MathServe
  r)ar.AsyncState
• double result obj1.EndAdd(ar)

58
Asynchronous Call Using Polling

• localhost.MathServer obj new
  localhost.MathServer()
• IAsyncResult ar obj.BeginAdd
  (firstNumber, secNumber, delaySecs, null,
  null)
• Console.WriteLine("I am not blocked")
• if (ar.IsCompleted true)
•     double result obj.EndAdd(ar)
• Console.WriteLine("Addition result is "
  result.ToString() )

59
Exception Handling

• Exception is repackaged as a SoapException and is
  returned to the Web service client via the SOAP
  response
• Exceptions are sent back to the client in the
  form of a SOAP ltFaultgt XML element within a SOAP
  message that specifies when an error occurred
• The three predefined subelements are ltfaultCodegt,
  ltfaultStringgt, and ltdetailgt, and you can define
  your own subelements that belong to an
  application-specific namespace

60
SoapException

• SoapException has eight overloaded constructors,
  two of which take in an array of XML nodes.
• For example
•  
• public SoapException( string message,
• XmlQualifiedName code, string actor,
• XmlNode detail )

61
Throw a SoapException with Detailed Error
Information

• try
• //do something
• catch
• XmlDocument doc new XmlDocument()
• System.Xml.XmlNode detail
  doc.CreateNode(XmlNodeType.Element,
  
  SoapException.DetailElementName.Name,
  SoapException.DetailElementName.Namespace
  )
• detail.InnerText "This is the detail part
  of my sample exception
• throw new SoapException("Message string from
  your Web service", SoapException.ServerFaultCode,
  Context.Request.Url.AbsoluteUri, detail)

62
The Serialized SoapException Results in a
ltsoapFaultgt

• lt?xml version"1.0" encoding"utf-8"?gt
• ltsoapEnvelope xmlnssoap"http//schemas.xmlsoap.
  org/soap/envelope/"gt
• ltsoapBodygt
• ltsoapFaultgt
• ltfaultcodegtsoapServerlt/faultcodegt
• ltfaultstringgtSystem.Web.Services.Protocols.S
  oapException Message string from your Web
  service
• at ThrowExceptionService.Service1.division(
  Int32 x, Int32 y) in c\inetpub\wwwroot\throwexcep
  tionservice\service1.asmx.csline
  111lt/faultstringgt
• ltfaultactorgthttp//localhost81/ThrowExcepti
  onservice/service1.asmxlt/faultactorgt
• ltdetailgtThis is the detail part of my
  sample exception lt/detailgt
• lt/soapFaultgt
• lt/soapBodygt
• lt/soapEnvelopegt

63
Catching SoapExceptions on the Client Side

• try
• localhost.Service1 obj new localhost.Service1(
  )
• double result obj.division(9,0)
• catch(System.Web.Services.Protocols.SoapException
  se)
• Console.WriteLine("Server threw a soap
  exception, se.Message)
• catch(System.Exception ee)
• Console.WriteLine("It was not a soap
  exception", ee.Message )

64
Transactions in Web Services

• The TransactionOption property of the WebMethod
  attribute specifies how an XML Web service method
  participates in a transaction
• XML Web service methods can only participate in a
  transaction as the root of a new transaction
• XML Web service methods that call other XML Web
  service methods participate in different
  transactions because transactions do not flow
  across XML Web service methods

65
Enabling Transaction Support

• Add reference to the System.EnterpriseServices
  namespace
• Declare an XML Web service method, setting the
  TransactionOption property of the WebMethod
  attribute to TransactionOption.RequiresNew

Possible Values for TransactionOption
66
Transactional WebMethod

• WebMethod(TransactionOptionTransactionOption.Req
  uiresNew)
• public int DeleteAuthor(string lastName)
• String deleteCmdSQL "DELETE FROM authors WHERE
  au_lname'" lastName "'"
• String exceptionCausingCmdSQL "DELETE FROM
  NonExistingTable WHERE au_lname'"
  lastName "'"
• SqlConnection sqlConn new SqlConnection( "user
  idsa databasepubs servermyserver")
• SqlCommand deleteCmd new SqlCommand(deleteCmdSQ
  L,sqlConn)
• SqlCommand exceptionCausingCmd new
  sqlCommand (exceptionCausingCmdSQL,sqlConn)
  
• deleteCmd.Connection.Open()
• deleteCmd.ExecuteNonQuery()
• int cmdResult exceptionCausingCmd.ExecuteNonQue
  ry()
• sqlConn.Close()
• return cmdResult

67
Web Services Discovery Challenges

• Who provides Web services?
• How are they implemented?
• Where are they exposed?
• What are they for?
• What is their behavior?
• How do I incorporate run time interaction?
• How do I publish my Web service?

68
Discovery and UDDI

• Discovery is the process of locating a Web
  service and interrogating it
• .disco is an XML document that typically points
  to a WSDL (or some other description file) that
  points to an actual Web service
• ltdiscodiscovery xmlnsdisco"http//schemas.xmls
  oap.org/disco/" xmlnsscl"http//schemas.xmlsoap.
  org/disco/scl/"gt
• lt!-- reference to other DISCO document --gt
• ltdiscodiscoveryRef ref"related-services/default
  .disco"/gt
• lt!-- reference to WSDL and documentation --gt
• ltsclcontractRef ref"math.asmx?wsdl"
  docRef"math.asmx"/gt lt/discodiscoverygt

69
Dynamic Discovery

• Enables clients to discover all Web services on
  your Web server.
• Requests for .vsdisco files are handled by
  System.Web.Services.Discovery.DiscoveryRequestHand
  ler. It searches recursively through all
  subdirectories, looking for .asmx and .disco
  files.
• The .vsdisco file is in the root directory of the
  Web application.
• lt?xml version"1.0" encoding"utf-8" ?gt
• ltdynamicDiscovery xmlns"urnschemas- dynamicdisc
  overydisco.2000-03-17"gt
• ltexclude path"_vti_cnf" /gt
• ltexclude path"_vti_pvt" /gt
• ltexclude path"_vti_log" /gt
• ltexclude path"_vti_script" /gt
• ltexclude path"_vti_txt" /gt
• ltexclude path"Web References" /gt
• ltexclude path"MyFolder" /gt
• lt/dynamicDiscoverygt

70
Disco Document When Browsed to the .vsdisco File

• lt?xml version"1.0" encoding"utf-8" ?gt
• - ltdiscovery xmlnsxsd"http//www.w3.org/2001/XML
  Schema" xmlnsxsi"http//www.w3.org/2001/XMLSchem
  a-instance" xmlns"http//schemas.xmlsoap.org/disc
  o/"gt
•   ltdiscoveryRef ref"http//localhost/MyMathServic
  e/MyMathService.vsdisco" /gt
•   ltdiscoveryRef ref"http//localhost/CreditCardCh
  eckServiceCS/CreditCardCheckServiceCS.vsdisco" /gt
  
•   ltdiscoveryRef ref"http//localhost/AsyncMathSer
  vice/AsyncMathService.vsdisco" /gt
•   lt/discoverygt

71
Disco Document that is Composed Dynamically

• lt?xml version"1.0" encoding"utf-8" ?gt
• ltdiscovery xmlnsxsd"http//www.w3.org/2001/XMLSc
  hema" xmlnsxsi"http//www.w3.org/2001/XMLSchema-
  instance" xmlns"http//schemas.xmlsoap.org/disco/
  "gt
•   ltcontractRef
• ref http//localhost/AsyncMathService/MathServer
  .as mx?wsdl" docRef"http//localhost/AsyncMathSe
  rvice/MathServer .asmx" xmlns"http//schemas.x
  mlsoap.org/disco/scl/" /gt
• lt/discoverygt

72
UDDI (Universal Discovery, Description, and
Integration)

• UDDI is an industry specification for description
  and discovery of Web services
• Enables publish, find, and bind functions of
  Web services

Registry operator node
UDDI service cloud
Registry operator node
UDDI Find
UDDI Publish
Client
Service provider
73
UDDI Registry
74
UDDI Data Structures

• businessEntity
• The white pages of UDDI. Contains basic business
  information name, description, contact
  information.

ltbusinessEnitity authorizedName0968869
businessKeyA234567-XXXX-XXXX-XXXXXXXX
operatoruddi.microsoft.comgt ltdisco
veryURLsgt ltdiscoveryURLgthttp//uddi.microsoft.com
/services/uddi/uddiget?businessKey
A234567-XXXX-XXXX-XXXXXXXX lt/discoveryURLgt lt/disco
veryURLsgt ltnamegtXYZ Corporationlt/namegt ltdescriptio
ngt...lt/descriptiongt ltcontactsgt ltpersonamegtXYZ
lt/personnamegt ltphonegt..lt/phonegt lt/contactsgt ltbus
inessServicesgt ltbusinessService
businessKeyA234567-XXXX-XXXX-XXXXXXXX
serviceKey7859484-XXXX-XXXX-XXXXXXX
X lt/businessServicessgt lt/businessEntitygt
75
UDDI Data Structures (2)

• businessService
• Yellow pages of UDDI. Categorizes Web services
  by industry, product, or service and location.
  Based on industry standards like NAICS and
  UNSPSC.
• ltbusinessService businessKeyA234567-XXXX-XXXX-XX
  XXXXXX
• serviceKey7859484-XXXX-XXXX-XXX
  XXXXX
• ltnamegt Sample PurchaseService1lt/namegt
• ltdescriptiongt This service enables purchasing
  from XYZlt/descriptiongt
• ltbindingTemplatesgt ...lt/bindingTemplatesgt
• ltcategoryBaggt
• ltkeyedReference keyNameUNSPSCShopping
  software
• keyValue 123456
• tModelKeyUUIDABG5678-XXXX-XXXX-XXXX /gt
• lt/categoryBaggt
• lt/businessServicegt

76
UDDI Data Structures (3)

• bindingTemplate
• Green pages of UDDI. Contains technical
  information the service descriptions and the
  binding information to call a Web service.
• ltbindingTemplate bindingKey7867..
• serviceKey7859484-XXXX-XXXX-XXXXXXXX
• ltdescriptiongtlt/descriptiongt
• ltaccessPoint URLTypehttpgt
• http//www.xyz.com/ lt/accessPointgt
• lttModelInstanceDetailsgt
• lttModelInstanceInfo tModelKeyUUID76875
  -/gt
• lt/tModelInstanceDetailsgt
• lt/bindingTemplategt

77
UDDI Data Structures (4)

• tModel
• A pointer to a technical specification.
• lttModel authorizedName0968869
• operatoruddi.microsoft.com
• tModelKeyUUID76875-gt
• ltnamegt.lt/namegt
• ltdescriptiongt. lt/descriptiongt
• ltoverviewDocgt
• ltoverviewURLgthttp//www.uddi.org/specific
  ation.htmllt/overviewURLgt
• lt/overviewDocgt
• lt/tModelgt

78
UDDI Programmer's API

• Inquiry API
• Provides operations for retrieving information
  from the registry.
• Publishing API
• Provides operations for publishing information
  to the registry.

UDDI Inquiry API
Name
Description
79
UDDI Publishing API
Name
Description
80
Samples Available for Download

• SimpleService simple service
• StateManagementDemo state management
• SoapHeaders SOAP headers
• SoapTraceExtension SOAP extensions
• SoapCustomMessage formatting SOAP messages
• SecureWebService Web service security
• ASysnchronousMathService async call
• ExceptionService SoapException

81
References

• MSDN Visual Studio .NET documentation
• http//www.uddi.org
•  http//uddi.microsoft.com

82

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