1. GWT - RPC

2. RPC plumbing diagram

3. 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); }

4. 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; } }

5. 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); }

6. Deploy service Tomcat -> add Servlet
Hosted mode -> modify module XML
<module>
<inherits name='com.google.gwt.user.User'/>
<entry-point class='com.mycompany.client.MyApplication'/>
<servlet path="/addService" class="com.mycompany.server.MyAddServiceImpl“/>
</module>

7. Actually making a call instantiate service interface
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

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);
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

9. Actually making a call actually make the 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

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);
} } );