GWT.setUncaughtExceptionHandler() - gwt

Question

Has anyone successfully used the above statement to catch the exception before it goes to the browser as an alert?.
I registered a custom Exception Handler in the first line of my application entry point. But it does not catch the exception as expected.
public void onModuleLoad(){
GWT.setUncaughtExceptionHandler(new MyExceptionHandler());
...
....
}
EDIT
Here are my two classes:
I expect my system.out will print the details of the exception
and exception will be swallowed and should not be sent to browser.
Or Am I wrong?
package mypackage;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
public class MyEntryPoint implements EntryPoint {
public void onModuleLoad() {
GWT.setUncaughtExceptionHandler(new ClientExceptionHandler());
startApplication();
}
private void startApplication() {
Integer.parseInt("I_AM_NOT_NUMBER");
}
}
package mypackage;
import com.google.gwt.core.client.GWT;
public class ClientExceptionHandler implements GWT.UncaughtExceptionHandler {
#Override
public void onUncaughtException(Throwable cause) {
System.out.println(cause.getMessage());
}
}

Answer 1

I believe what's happening here is that the current JS event cycle is using the DefaultUncaughtExceptionHandler because that was the handler set at the start of the cycle. You'll need to defer further initialization to the next event cycle, like this:
public void onModuleLoad() {
GWT.setUncaughtExceptionHandler(new ClientExceptionHandler());
Scheduler.get().scheduleDeferred(new ScheduledCommand() {
#Override
public void execute() {
startApplication();
Window.alert("You won't see this");
}
});
}
private void startApplication() {
Integer.parseInt("I_AM_NOT_A_NUMBER");
// or any exception that results from server call
}
Update: And here's the issue that describes why this works, and why it isn't planned to be fixed.

Answer 2

Setting up a default handler can be a tricky proposition some times. I can tell you exactly what is going on. If you get an exception in the onModuleLoad(), the handler will not be called. It is only after the load method is completed that it will ACTUALLY get put into place.

Answer 3

You should try the following:
public void onModuleLoad(){
GWT.setUncaughtExceptionHandler(new UncaughtExceptionHandler() {
onUncaughtException(Throwable t) {
// Do stuff here
}
});
}
and see if that helps.

Answer 4

Silly solution, but it works fine!
before anything add your EntryPoint in your app.gwt.xml
<entry-point class='myPackage.client.MyEntryPoint' />
then;
import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.core.client.GWT;
import com.google.inject.Inject;
import com.google.web.bindery.event.shared.EventBus;
public class MyEntryPoint implements EntryPoint {
private EventBus eventBus;
#Inject
public MyEntryPoint(final EventBus eventBus){
this.eventBus = eventBus;
}
#Override
public void onModuleLoad() {
CustomUncaughtExceptionHandler customUncaughtExceptionHandler = new CustomUncaughtExceptionHandler();
GWT.setUncaughtExceptionHandler(customUncaughtExceptionHandler);
try {
onModuleLoad2();
} catch (RuntimeException ex) {
eventBus.fireEvent(new BusyEvent(false));
customUncaughtExceptionHandler.onUncaughtException(ex);
}
}
private void onModuleLoad2() {
throw new RuntimeException("test");
}
}
and your CustomUncaughtExceptionHandler would be something like:
import com.google.gwt.core.client.GWT.UncaughtExceptionHandler;
import com.google.gwt.event.shared.UmbrellaException;
import com.google.gwt.user.client.Window;
public class CustomUncaughtExceptionHandler implements UncaughtExceptionHandler {
#Override
public void onUncaughtException(Throwable e) {
Throwable exceptionToDisplay = getExceptionToDisplay( e );
Window.alert( exceptionToDisplay.getCause() .getMessage()+" "+ exceptionToDisplay.getStackTrace());
}
private static Throwable getExceptionToDisplay( Throwable throwable ) {
Throwable result = throwable;
if (throwable instanceof UmbrellaException && ((UmbrellaException) throwable).getCauses().size() >= 1) {
result = ((UmbrellaException) throwable).getCauses().iterator().next();
}
return result;
}
}