INFOSYS 290, Section 3, Fall 2005, Web Services: Concepts, Design and Implementation Adam Blum Lecture 4: Creating Web Services

Today’s Content Creating Web Services Overview Demo Web Service Creation –Raw computation –Database –HTML scraping –XML wrapping –SOAP web service wrapping Break To Set Up Environments –MindReef SOAPScope –AboveAll –Visual Studio Redemo of Consuming Web Services – MindReef –AboveAll –Visual Studio Lecture: Asynchronous Web Services

Creating Web Services Create a web service project Design the interface –Demoing “method-oriented interfaces” today Place [WebMethod] around the exposed methods Write your internal logic Test with Visual Studio and debug

Example Web Services Demonstrating Various Techniques Raw computation –PokerOdds ( 3/f05/samples/PokerOdds) Database creation –ProjectTraq –Workouts XML wrapping –Blogs ( 3/f05/samples/PokerOdds) –SportsBetLines ( 3/f05/samples/PokerOdds) HTML/HTTP scraping –PokerOdds AnalyzeHands() SOAP web service wrapping –SalesForce

Informational Web Services QCUD Multiple records in query Doesn’t have to have CUD Richly descriptive records Generally comes from a persisted store Contrast with computation or transactional web service

Informational Web Service Examples Sales accounts, contacts, tasks, opportunities Project bugs Helpdesk, customer support items Blog entries Newsfeeds

Consuming Web Services Ad hoc tools and management systems –E.g. MindReef SOAPScope Forms design environments –E.g. AboveAll Studio Third generation traditional programming environments –E.g. Visual Studio.NET 2005

Asynchronous Web Services

Why Asynchronous Web Services? Speed –Due to overhead of XML and http XML web services can be SLOW Unpredictability –Your app may be invoking a web service that itself is slow, unreliably available or involves a human in the process Size –Moving to larger coarsegrained documents and less frequent chatty method calls can introduce more overhead Blocking on downstream services creates instant bottlenecks in your application

Creating Asynchronous Web Services Write “begin” and “end” methods versus single invocation methods VisualStudio.NET generates: –public System.IAsyncResult BeginValidate Address(string Address, System.AsyncCallback callback, object asyncState) { – return this.BeginInvoke("Validate Address", new object[] { Address}, callback, asyncState); –} –public Check Result EndValidate Address(System.IsyncResult asyncResult) { – object[] results = this.EndInvoke(asyncResult); – return ((Check Result)(results[0])); –}

Invoking Asynchronous Web Services Polling Blocking Callbacks

Polling // polling version private void Command1_Click(object sender, System.EventArgs e) { validatorproxy=new Einsteinware. Services(); int start=DateTime.Now.Second; IAsyncResult ar= validatorproxy.BeginValidate Address(TextBox1.Text, null,null); while (!ar.IsCompleted){ –//do stuff } switch( validatorproxy.EndValidate Address(ar)){ –case Einsteinware.Check Result.Valid: Label1.Text="Valid"; break; –default: Label1.Text="Invalid"; break; }

Blocking private void Command1_Click(object sender, System.EventArgs e) { validatorproxy=new Einsteinware. Services(); IAsyncResult ar= validatorproxy.BeginValidate Address(TextBox1. Text,cb, validatorproxy); // do lots of stuff ar.AsyncWaitHandle.WaitOne(); switch(response) { case Einsteinware.Check Result.Valid: Label1.Text="Valid"; break; default: Label1.Text="Invalid"; }

WaitHandle Object WaitOne –Waits for this one handle WaitAny –Static method which takes array of WaitHandles, returns when any have completed WaitAll –Returns when all have completed

Invoking with a Callback // callback version private void Command1_Click(object sender, System.EventArgs e) { validatorproxy=new Einsteinware. Services(); // instantiate the AsyncCallback delegate AsyncCallback cb = new AsyncCallback( validatorCallback); int start=DateTime.Now; IAsyncResult ar= validatorproxy.BeginValidate Address( TextBox1.Text,cb,null); Label1.Text=Label1.Text + "(" + System.Convert.ToString( DateTime.Now.CompareTo(start) ")"; }

The Callback Itself public delegate void MyDelegate(Label l,String s); private void validatorCallback(System.IAsyncResult ar) { Check Result response= validatorproxy.EndValidate Address(ar); switch(response) { case Check Result.Valid: message="Valid"; break; … } responseLabel.Invoke( new MyDelegate(DisplayResponse),new object[]{label1,message}); } private void DisplayResponse(Label label,String message) { label.Text=message; Form1.ActiveForm.Refresh(); } Remember: callbacks are on a separate thread and need a way to communicate back to the main thread to display…hence delegates

Using the Async State Object // using async state to handle two label objects private void button1_Click(object sender, System.EventArgs e) { label1.Text="";label2.Text=""; validatorproxy=new Einsteinware. Services(); IAsyncResult ar= validatorproxy.BeginValidate Address( textBox1.Text,new AsyncCallback( validatorCallback),label1); IAsyncResult ar2= validatorproxy.BeginValidate Address( textBox1.Text,new AsyncCallback( validatorCallback),label2); }

Callback Using the Async State Object private void validatorCallback(System.IAsyncResult ar) { –Check Result response= validatorproxy.EndValidate Address(ar); –String message=""; –switch(response) –{ –case EinsteinwareCheck Result.Valid: message="Valid“; break; –case Check Result.InvalidUser: message="Invalid user"; break; … –} –Label responseLabel = (Label)ar.AsyncState; –responseLabel.Invoke(new MyDelegate(DisplayResponse),new object[]{responseLabel,message}); }

Course Project Goal –Build “web service consuming” client applications from desktops and mobile devices Requirements –Use an “informational” web service Has QCUD (Query, Create, Update and Delete operations) Query returns MULTIPLE records –Consume web service from AboveAll or Visual Studio for desktop –Consume WS from GoodAccess Web Services or Visual Studio from mobile device –Optionally write or enhance a backend web service Possibly as a “proxy web service” layer on top of original web service Only if previous steps are achieved –Demo to class –Write up as three page paper including: architecture and UI design Team size –Two people per project Proposal –Due today, will accept later

References Specs –SOAP Specification, –WSDL Specification, –UDDI Specification, Tools –Visual Studio, –Microsoft Web Services Enhancements

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