Modified GWT sample module code - using JSNI - call JS method from JAVA - call JAVA method from JS

/**
 * Entry point classes define <code>onModuleLoad()</code>.
 */
public class JSTransliterate implements EntryPoint {

public void handleResult(JsArrayString list){
serverResponseLabel.setHTML(list.get(0) + ":" + list.get(1));
}
public static native void alert(String msg) /*-{
 $wnd.alert(msg);
}-*/;

public native void transliterate(JsArrayString words) /*-{
 $wnd.alert(words[1]);
 var ret = ["ret1", "ret2", "ret3"];
 this.@org.bvp.be.client.JSTransliterate::handleResult(Lcom/google/gwt/core/client/JsArrayString;)(ret);
}-*/;

/**
* The message displayed to the user when the server cannot be reached or
* returns an error.
*/
private static final String SERVER_ERROR = "An error occurred while "
+ "attempting to contact the server. Please check your network "
+ "connection and try again.";

/**
* Create a remote service proxy to talk to the server-side Greeting service.
*/
private final GreetingServiceAsync greetingService = GWT
.create(GreetingService.class);


final HTML serverResponseLabel = new HTML();

/**
* This is the entry point method.
*/
public void onModuleLoad() {
final Button sendButton = new Button("Send");
final TextBox nameField = new TextBox();
nameField.setText("GWT User");
final Label errorLabel = new Label();

// We can add style names to widgets
sendButton.addStyleName("sendButton");

// Add the nameField and sendButton to the RootPanel
// Use RootPanel.get() to get the entire body element
RootPanel.get("nameFieldContainer").add(nameField);
RootPanel.get("sendButtonContainer").add(sendButton);
RootPanel.get("errorLabelContainer").add(errorLabel);

// Focus the cursor on the name field when the app loads
nameField.setFocus(true);
nameField.selectAll();

// Create the popup dialog box
final DialogBox dialogBox = new DialogBox();
dialogBox.setText("Remote Procedure Call");
dialogBox.setAnimationEnabled(true);
final Button closeButton = new Button("Close");
// We can set the id of a widget by accessing its Element
closeButton.getElement().setId("closeButton");
final Label textToServerLabel = new Label();
VerticalPanel dialogVPanel = new VerticalPanel();
dialogVPanel.addStyleName("dialogVPanel");
dialogVPanel.add(new HTML("<b>Sending name to the server:</b>"));
dialogVPanel.add(textToServerLabel);
dialogVPanel.add(new HTML("<br><b>Server replies:</b>"));
dialogVPanel.add(serverResponseLabel);
dialogVPanel.setHorizontalAlignment(VerticalPanel.ALIGN_RIGHT);
dialogVPanel.add(closeButton);
dialogBox.setWidget(dialogVPanel);

// Add a handler to close the DialogBox
closeButton.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
dialogBox.hide();
sendButton.setEnabled(true);
sendButton.setFocus(true);
}
});

// Create a handler for the sendButton and nameField
class MyHandler implements ClickHandler, KeyUpHandler {
/**
* Fired when the user clicks on the sendButton.
*/
public void onClick(ClickEvent event) {
sendNameToServer();
}

/**
* Fired when the user types in the nameField.
*/
public void onKeyUp(KeyUpEvent event) {
if (event.getNativeKeyCode() == KeyCodes.KEY_ENTER) {
sendNameToServer();
}
}

/**
* Send the name from the nameField to the server and wait for a response.
*/
private void sendNameToServer() {
// First, we validate the input.
errorLabel.setText("");
String textToServer = nameField.getText();
if (!FieldVerifier.isValidName(textToServer)) {
errorLabel.setText("Please enter at least four characters");
return;
}

// Then, we send the input to the server.
sendButton.setEnabled(false);
textToServerLabel.setText(textToServer);
serverResponseLabel.setText("");
greetingService.greetServer(textToServer,
new AsyncCallback<String>() {
public void onFailure(Throwable caught) {
// Show the RPC error message to the user
dialogBox
.setText("Remote Procedure Call - Failure");
serverResponseLabel
.addStyleName("serverResponseLabelError");
serverResponseLabel.setHTML(SERVER_ERROR);
dialogBox.center();
closeButton.setFocus(true);
}

public void onSuccess(String result) {
dialogBox.setText("Remote Procedure Call");
serverResponseLabel
.removeStyleName("serverResponseLabelError");
serverResponseLabel.setHTML(result);
dialogBox.center();
closeButton.setFocus(true);
// alert("Success");
JsArrayString list = (JsArrayString) JsArrayString.createArray();
list.push("str1");
list.push("str2");
list.push("str3");
transliterate(list);
}
});
}
}

// Add a handler to send the name to the server
MyHandler handler = new MyHandler();
sendButton.addClickHandler(handler);
nameField.addKeyUpHandler(handler);
}
}