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Creating an Asynchronous Service Definition Interface in Java Implementation barcode 128 in Java Creating an Asynchronous Service Definition Interface

Creating an Asynchronous Service Definition Interface use jsp code-128 generating touse barcode standards 128 in java Visual Studio 2005 The interface cre Code128 for Java ated in the previous task is a synchronous one. In order to take advantage of the AJAX support in GWT, we will need to create the asynchronous version of this interface, which will be used for making remote calls in the background to the server..

Time for Action Utilizing the AJAX Support In this section, Code 128B for Java we will create an asynchronous version of the service definition interface. Create a new Java file named PrimesServiceAsync.java in the com.

packtpub. gwtbook.samples.

client package. Define a PrimesServiceAsync interface:. public interface PrimesServiceAsync { public void isPrimeNumber(inr numberToVerify, AsyncCallbackcallback); }. [ 37 ]. Creating Services What Just Happened The asynchronous version of our service definition interface must have the same methods as the synchronous interface, except for the requirement that all of its methods must have an AsyncCallback object as a parameter, and the methods may not return anything. The callback object acts as the binding between the client and the server. Once an asynchronous call is made by the client, the notification, when the call completes its processing on the server side is made through this callback object.

Essentially this makes the AJAX magic happen! You do not have to do anything special for all this magic to happen, other than making sure that you provide this asynchronous interface for your service definition. The GWT framework will automatically take care of all the communication between the client and the server. A client application that is using this service will invoke the service through this method, passing it a callback object and will automatically be notified of either success through a callback to the onSuccess() method in the client application or failure through a callback to the onFailure() method in the client application.

The current release of GWT only supports making an asynchronous call back to the server. Even though the service definition interface is synchronous, that does not mean that you can use it to make a synchronous call to the server. So any service that you build using GWT can currently only be accessed asynchronously via AJAX.

. Creating a Service Implementation We have so far cr eated the interfaces that define the functionality of our Prime Number service. In this section, we are going to start implementing and filling out the service class and create the actual implementation of the Prime Number service..

Time for Action Implement Our Service We are going to c reate the implementation of the Prime Number service. It checks to see if the provided number is a prime number by ensuring that it is only divisible by one and itself. The verification result is returned as a Boolean value.

Create a new Java file, named PrimesServiceImpl.java in the com.packtpub.

gwtbook.samples.server package.

Define a PrimesServiceImpl class that extends RemoteServiceServlet and implements the previously created PrimesService interface. Add functionality to this class to verify if the provided number is a prime number..

public class Prim Java Code 128C esServiceImpl extends RemoteServiceServlet implements PrimesService { private static final long serialVersionUID = -8620968747002510678L; [ 38 ]. 3 public boolean isPrimeNumber(int numberToVerify) { boolean isPrime = true; int limit = (int) Math.sqrt ( numberToVerify ); for ( int i = 2; i <= limit; i++ ) { if(numberToVerify % i == 0 ) { isPrime = false; break; } } return isPrime; } }. What Just Happened Since this is the implementation of the Prime Number service, this class needs to implement the service definition interface, and add functionality to the implemented methods. This task and the previous tasks delineate the steps that are always required in order to create a GWT service. Creating and using RPC services is a critical step on the path to unlocking the power of GWT and for using it efficiently and effectively.

The basic architecture of a GWT application consists of a client-side user interface that is rendered in a web browser and interacts with the server-side functionality implemented as an RPC service to asynchronously retrieve data and information without refreshing the page. The service in a GWT application wraps the server-side model of an application, and thus usually maps to the role of a model in the MVC architecture..

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