Handling custom Exception with GWT

Question

I am trying to make a the code that will catch a PhoneNumberInUseException that is thrown by the ServiceImpl however, the code below always go for the else statement.

@Override
            public void onFailure(Throwable caught) {
                Window.alert("Failed create account.");
                if (caught instanceof PhoneNumberInUseException) {
                    Window.alert("Sorry, but the phone number is already used.");
                } else {
                    Window.alert(caught.toString());
                }

            }

The PhoneNumberInUseException extends RuntimeException

Right now I am just showing this through Window.alert, however I will be doing client-side logic for handling the exception, that is why I can't simply use IllegalArgumentException which works just fine passing exception string from server to client.

Am I missing something?

Chris Cashwell · Accepted Answer · 2011-12-13 15:48:25Z

If your PhoneNumberInUseException class looks something like this:

public class PhoneNumberInUseException extends RuntimeException {

    public PhoneNumberInUseException() {
        super();
    }
}

and you're throwing it in the service like this:

throw new PhoneNumberInUseException();

then your code should be firing correctly. That is, of course, assuming your service has declared that it throws PhoneNumberInUseException, like this:

public interface SomeService extends RemoteService {
    void doSomething(Object someObject) throws PhoneNumberInUseException;
}

public interface SomeServiceAsync {
    void doSomething(Object someObject, AsyncCallback callback);
}

public class SomeServiceImpl extends RemoteServiceServlet implements SomService {
    public void doSomething(Object someObject) throws PhoneNumberInUseException {
        if(somethingHappened) {
            throw new PhoneNumberInUseException();
        } else {
            doSomethingCool();
        }
    }
}

If after you've made sure everything should be working correctly, you might want to put a breakpoint on the line

if (caught instanceof PhoneNumberInUseException)

and figure out what the class of caught is. If it's not PhoneNumberInUseException, you probably haven't read the documentation very well.

quarks · Accepted Answer · 2011-12-13 08:09:39Z

0

I had to extend PhoneNumnberInUseException from IllegalArgumentException instead of just Exception and make it Serializable, I don't know if this is the correct approach though:

public class PhoneNumnberInUseException extends IllegalArgumentException implements Serializable{
    public PhoneNumnberInUseException(){
        super();
    }
    public PhoneNumnberInUseException(String msg) {
        super(msg);
    }
}

answered Dec 13, 2011 at 8:09

quarks

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2 Comments

Chris Cashwell Over a year ago

Realistically, you could have kept your code exactly as it was and just declared that your RPC method throws that exception: public void doSomething(Object someObject) throws PhoneNumberInUseException;. GWT would only propagate a RuntimeException to the client if it had been explicitly declared via throws.

quarks Over a year ago

@ChrisCashwell I see, the reason I used RuntimeException is because I need to throw exception inside a if-else statement, whereas if I extend from Exception I'm getting syntax error.

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