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    Add as FriendWeb Services

    by: Rogers

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    1 : 9. Web Services
    2 : Objectives “Web Services are poised to change the future of software development...” WebServices
    3 : Web services? “Web services are web apps that return data, not presentation. Since applications are typically about accessing data, web services are poised to become the next evolutionary step in distributed software development...” Why? cross-platform application development legacy system integration obj obj obj Web server XML
    4 : Overview Web services involve many technologies: WSDL to learn about web service to call: proxy objects, SOAP, XML, HTTP and .ASMX pages obj obj Web server client app proxy method call HTTP request SOAP msg (XML) .asmx web service method call WSDL
    5 : Example Google A great search engine but what if I want my own GUI?
    6 : Google web service Google offers a web service that performs searches for you Why? clients can build custom GUIs can make money! // ask google to search for us... google = new GoogleSearchService(); result = google.doGoogleSearch("4a8/TvZQFHID0WIWnL1CMmMx0sNqhG8H", txtSearch.Text, 0, 10, false, "", false, "", "", ""); // display resulting URLs... foreach (ResultElement re in result.resultElements) lstURLs.Items.Add(re.URL);
    7 : Working with web services Two steps: build a web service build clients to use it
    8 : (1) Building a web service Start by creating a project of type “ASP.NET Web Service”
    9 : A web service is… One or more objects that respond to web-based method calls there is no GUI design to a web service only raw classes with methods… public class Service1 : System.Web.Services.WebService { . . . }
    10 : Example Looks like C#, but keep in mind these are web-based methods client could be calling from any platform parameters passed using XML public class Service1 : System.Web.Services.WebService { [WebMethod] public int Add(int x, int y) { return x + y; } [WebMethod] public string[] Attendees() { <> } } attribute inherit
    11 : (2) Building a client Start by creating a client… WinForm, WebForm, console-based, anything you want! for fun, let's use VB…
    12 : Reference the component As usual, we need to reference component this will activate IntelliSense this will make sure we call it correctly this will enable underlying XML + SOAP communication How? project references, right-click, Add web reference… type URL for web service, e.g. http://localhost/WebService/Service1.asmx service name classname web server
    13 : Program against component Treat web service like any other class! use new to create instances make method calls pass parameters Private Sub Button1_Click(...) Handles Button1.Click Dim i, j, k As Integer i = CInt(TextBox1.Text) j = CInt(TextBox2.Text) Dim obj As localhost.Service1 obj = New localhost.Service1() k = obj.Add(i, j) MessageBox.Show("Sum = " + k.ToString()) End Sub
    14 : Underlying execution… Here's what the call to Add() actually looks like: Web server client app proxy obj.Add(i, j); HTTP request: Service1.asmx 10 20 .asmx web service obj.Add(10, 20);
    15 : Summary Pretty powerful stuff! Lots of technology be used underneath: XML for parameter-passing SOAP as protocol HTTP ASP.NET IIS
    16 : References Books: Y. Shohoud, "Real World XML Web Services: for .NET and VB .NET Developers" Web sites:
    17 : Lab? Work on lab #6, "Web Services"…

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