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Web Services Introduction
ISYS 546
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Web Service XML Web Service
Web services are classes that are stored on the web which can instantiate and use in both Windows and Web applications.
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Creating a Web Service Using a Text Editor
WebService directive: WebService Class="CustomerInfo" %> Import namespaces: imports System.Web.Services imports System Define the web service class. Add WebMethod attribute to the function declaration. Note: Web service file extension is ASMX
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A Web Service Example ASPET/TestWebService.ASMX
WebService Class="CustomerInfo" %> imports System.Web.Services imports System imports System.Data imports System.Data.Oledb Public Class CustomerInfo <webMethod()> public Function GetCname(ByVal CID as String) as String dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb" dim objConn as new OledbConnection(strConn) dim strSQL as string = "select * from customer where CID = '" & CID & "';" dim objComm as new OledbCommand(strSQL,objConn) dim Results as string objConn.open() dim objDataReader as oledbDataReader objDataReader=objComm.executeReader() objDataReader.read() return objDataReader("Cname") end function
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Creating a Web Service Using VS
New Project/ASP.Net Web Service
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Web Service Description Language (WSDL)
A WSDL file is an XML document containing a complete description of the web service. It shows a web service’s name, methods, and parameter types. Help page: After entering web service’s URL, a help page is displayed. You can click the Service Description link to see the WSDL file.
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HTTP HTTP Request: HTTP Response: Request line: Method – Get, Post
Header Body HTTP Response: Respons line: HTTP version and status code
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Invoking a Web Service with HTTP
Http – Get: Http – Post: Use the Action attribute to call the function. Http-SOAP: Use Http’s Post method to send an XML document in Https’ body section. Demo: Help page
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Simple Object Access Protocol SOAP
SOAP Request and Response message: Envelop: An envelop element surrounds the message. It is the root element of a SOAP XML document. Body: Request: Contains the method call name and parameter names and values. Response: Contains the results returned by the method.
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Consuming Web Services from a Windows Application
Add a web reference to the web service. Declare a web service class variable. Dim myWebService As New dchaolaptop.CustomerInfo() Demo: UseWebService
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Universal Description, Discovery, and Integration (UDDI)
A directory service for web services.
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Consuming Web Services from a Web Application
Creating a web service proxy class: A local representation of the web service. Steps to creating a proxy class: Use the Wsdl.exe tool to generate the source code file for the proxy class. Compile the source code file into a DLL file. Copy the DLL file to the application’s Bin folder.
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Use the Wsdl.Exe Tool to Generate the Source Code File
Issue the wsdl.exe command at the Visual Studio command prompt: Start/Programs/microsoft VS .Net/VS .Net Tools/ VS .Net Command prompt The following command example create a CustomerInfo.vb file for the testwebservice.asmx web service. wsdl.exe /l:vb
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Compile the Source Code File Into a DLL File
The command below create a CustomerInfo.dll Vbc /t:library /r:system.dll,system.web.services.dll,system.xml.dll CustomerInfo.vb
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<script runat="server">
sub CallService(s as object, e as eventArgs) dim myProxy as new CustomerInfo lblCname.text=myProxy.GetCname(txtCID.text) lblRating.text=myProxy.GetRating(txtCID.text) end sub </script> <html> </head> <body> <form runat="server"> Enter CID: <asp:textbox id="txtCID" runat="server" /> <asp:label id="lblCname" runat="server"/> <asp:label id="lblRating" runat="server"/> <asp:button text="GetService" onClick="CallService" runat="server" /> </form> </body> </html> Demo: testProxy.aspx
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