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EDT:Accessing a service

Revision as of 19:07, 13 February 2012 by Margolis.us.ibm.com (Talk | contribs)

You can access a service from a Rich UI application.

EDT version .8

In EDT version .8, your task is to code a call statement such as this one:

call MyInterface.myOperation() using "binding.myService" 
                               returning to myCallBackFunction
                               onException myExceptionHandler;

Your call statement typically has the following aspects:

  • Invokes a specific operation by referring either to a function in a Service type or to a function prototype in an Interface type.
  • Identifies service-access details in one of two ways:
    • By a string or string-type variable that refers to a service binding in an EGL deployment descriptor.
    • By a variable that is specific to a kind of service binding and that provides service-access details directly. You might have retrieved details from the EGL deployment descriptor and then customized them; or you might have created the details from scratch, in your code.

Accessing a dedicated service (version .8)

 

Accessing an EGL REST-RPC service (version .8)

 

Accessing a third-party REST service (version .8)

 


EDT version .7

In EDT version .7, your task follows this pattern:  declare a service-access variable and use it in a call statement.

Accessing a dedicated service (version .7)

// 1. declare the service-access variable
myService MyServiceType?{@dedicatedService}
 
// 2. call the service
call myService.theFunction() returning to theCallBack
                onException theExceptionHandler;
 
/*
 * Example: create a new EGL project for 
 * "Web 2.0 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 by 1)
         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.TextField;
import org.eclipse.edt.rui.widgets.GridLayoutData;
import dojo.widgets.DojoButton;
import dojo.widgets.DojoTextField;
 
handler MyHandler type RUIhandler{initialUI =[ui], 
             onConstructionFunction = start, 
             cssFile = "css/ProjectInEDT.7.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
        myService MyServiceType?{@DedicatedService};
        call myService.calculate(myList) 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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