1. GWT - RPC

2. The Objects com.google.gwt.user.client.rpc.RemoteService com.google.gwt.user.client.rpc.AsyncCallback com.google.gwt.user.client.rpc.ServiceDefTarget com.google.gwt.user.server.rpc.RemoteServiceServlet

3. RPC plumbing diagram

4. RPC plumbing diagram package com.mycompany.client; import com.google.gwt.user.client.rpc.RemoteService; public interface MyAddService extends RemoteService { public int add(int a, int b); }

5. RPC plumbing diagram package com.mycompany.server; import com.google.gwt.user.server.rpc.RemoteServiceServlet; import com.mycompany.client.MyAddService; public class MyAddServiceImpl extends RemoteServiceServlet implements MyAddService{ public int add(int a, int b) { int z = a + b; return z; } }

6. RPC plumbing diagram package com.mycompany.client; import com.google.gwt.user.client.rpc.AsyncCallback; public interface MyAddServiceAsync { public void add(int a, int b, AsyncCallback callback); }

8. Actually making a call button.addClickListener( new ClickListener() { public void onClick(Widget sender) { AddServiceAsync addService = (AddServiceAsync) GWT.create(AddService.class); ServiceDefTarget endpoint = (ServiceDefTarget) addService; String moduleRelativeURL = GWT.getModuleBaseURL() + "myAddService“; endpoint.setServiceEntryPoint(moduleRelativeURL); instantiate service interface set service implementation url

9. Actually making a call button.addClickListener( new ClickListener() { public void onClick(Widget sender) { AddServiceAsync addService = (AddServiceAsync) GWT.create(AddService.class); ServiceDefTarget endpoint = (ServiceDefTarget) addService; String moduleRelativeURL = GWT.getModuleBaseURL() + "myAddService“; endpoint.setServiceEntryPoint(moduleRelativeURL); AsyncCallback callback = new AsyncCallback(){ public void onSuccess(Object result){ resultaatLabel.setText(result.toString()); } public void onFailure(Throwable caught) { resultaatLabel.setText(caught.getMessage()); } create an asynchronous callback to handle the result

10. Actually making a call button.addClickListener( new ClickListener() { public void onClick(Widget sender) { AddServiceAsync addService = (AddServiceAsync) GWT.create(AddService.class); ServiceDefTarget endpoint = (ServiceDefTarget) addService; String moduleRelativeURL = GWT.getModuleBaseURL() + "myAddService“; endpoint.setServiceEntryPoint(moduleRelativeURL); AsyncCallback callback = new AsyncCallback(){ public void onSuccess(Object result){ resultaatLabel.setText(result.toString()); } public void onFailure(Throwable caught) { resultaatLabel.setText(caught.getMessage()); } }; addService.add(Integer.parseInt(aBox.getText()), Integer.parseInt(bBox.getText()), callback); } } ); actually make the call

11. Actually making a call button.addClickListener( new ClickListener() { public void onClick(Widget sender) { AddServiceAsync addService = (AddServiceAsync) GWT.create(AddService.class); ServiceDefTarget endpoint = (ServiceDefTarget) addService; String moduleRelativeURL = GWT.getModuleBaseURL() + "myAddService“; endpoint.setServiceEntryPoint(moduleRelativeURL); AsyncCallback callback = new AsyncCallback(){ public void onSuccess(Object result){ resultaatLabel.setText(result.toString()); } public void onFailure(Throwable caught) { resultaatLabel.setText(caught.getMessage()); } }; addService.add(Integer.parseInt(aBox.getText()), Integer.parseInt(bBox.getText()), callback); } } );

12. code executed on client side code executed on server side