EDT:Accessing a service

This page contains code snippets for service access.

You can access services from a Rich UI application.  If the logic for a given service is written in EGL, you might access that logic in the form of a dedicated service, in some cases, and might access the logic in the form of an EGL REST-RPC service at another. Here is one way to accomplish the task:

1. In your code, declare a binding variable and embed it in a call statement.
2. In the EGL deployment descriptor, define an entry.  To switch between accessing the logic in one form and accessing the logic in another, you can vary the entry in the same deployment descriptor or, more likely, can use a different deployment descriptor with a same-named entry.

Accessing a dedicated service

/********************************************************
 * Declare the binding variable                         * 
 ********************************************************/
   myBinding IHttp? = Resources.getResource("binding:myBinding");
 
/********************************************************
 * Call the service                                     * 
 ********************************************************/
   call MyServiceType.calculate(myList) 
      using myBinding
      returning to theCallBack 
      onException theExceptionHandler;
 
/********************************************************
 * Example: create a new EGL project for                *
 * "Web 2.0 client application with services". Add the  *
 * the Service type shown next to the server package,   * 
 * and add the Handler type to the client package.      *
 *                                                      *
 * Test the example in the Rich UI Preview tab          * 
 * by typing valid input into the first text box;       * 
 * for example: 5, 12, 4                                * 
 ********************************************************/
 
/********************************************************
 * The file with a Service type                         *
 ********************************************************/
package server;
 
service MyServiceType
 
   // variables and constants can be here
   function calculate(myScores Int[] in) returns(Decimal(4, 2))
      numberOfScores, i, mySum Int;
      numberOfScores = myScores.getSize();
 
      for(i from 1 to numberOfScores)
         mySum = myScores[i] + mySum;
      end
 
      return(mySum/numberOfScores);
   end 
end
 
/********************************************************
 * The file with a Handler type                         *
 ********************************************************/
package client;
 
import server.MyServiceType;
import org.eclipse.edt.rui.widgets.GridLayout;
import org.eclipse.edt.rui.widgets.GridLayoutData;
import org.eclipse.edt.rui.widgets.TextField;
import dojo.widgets.DojoButton;
import dojo.widgets.DojoTextField;
 
handler MyHandler type RUIhandler{initialUI =[ui], onConstructionFunction = start, 
                                  cssFile = "css/MyClientAppWithService.css", title = "MyHandler"}
 
   ui GridLayout{columns = 3, rows = 4, cellPadding = 4, children =[myResult, myButton, scores]};
 
   scores TextField{layoutData = new GridLayoutData{row = 2, column = 2}};
 
   myButton DojoButton{layoutData = 
      new GridLayoutData{row = 4, column = 2}, text = "Calculate", onClick ::= ui_onClick};
 
   myResult DojoTextField{layoutData = new GridLayoutData{row = 4, column = 3}};
 
   function start()
 
   end
 
   function theExceptionHandler(exp AnyException in)
 
      SysLib.writeStdOut(exp.messageID + " " + exp.message);
 
      if(exp isa ServiceInvocationException)
         SysLib.writeStdOut((exp as ServiceInvocationException).detail1);
         SysLib.writeStdOut((exp as ServiceInvocationException).detail2);
         SysLib.writeStdOut((exp as ServiceInvocationException).detail3);
      end
   end
 
   function theCallBack(retResult decimal(4, 2) in)
      myResult.text = retResult;
   end
 
   function ui_onClick(event Event in)
 
      inputLength int = scores.text.length();
 
      myDelimiters string = ", ";
      myPosition int = 1;
      myToken string;
      myList int[];
 
      while(myPosition < inputLength)
         myToken = StringLib.getNextToken(scores.text, myPosition, myDelimiters);
 
            if(myToken != null)
               myList.appendElement(myToken as int);
            end
      end
 
      /************ Service access statements ***************************/
 
      myBinding IHttp? = Resources.getResource("binding:myBinding");
      call MyServiceType.calculate(myList) 
         using myBinding
         returning to theCallBack 
         onException theExceptionHandler;
 
      /*******************************************************************/
 
   end
end

Accessing an EGL REST-RPC service (version .7)

Access of an EGL REST-RPC function is similar to accessing a dedicated service, but typically involves coding the variable declaration to reference an entry in the EGL deployment descriptor.

For example, you might change the previous handler to reference a deployment descriptor entry named myService. You can change the related variable declaration in one of two ways:

myService MyServiceType?{@Resource};
 
// or 
 
myService MyServiceType?{@Resource{bindingKey="myService"}};

You can demonstrate the access of a Service type under development only after you update two aspects of your deployment descriptor: Service Deployment and Resource Bindings. For details and a look at the version .8 code syntax, see Service bindings.

To retrieve the details from the HTTP response, add a parameter of type IHTTP to the callback function:

function theCallBack(retResult decimal(4, 2) in, myHttp IHTTP in)
 myResult.text = retResult;
 
 // display the response in JSON format
 SysLib.writeStdOut(myHttp.getResponse().body);
end

Accessing a third-party REST service (version .7)

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