Graceful exception handling in Swing Worker

Question

I am using threading in application through Swing Worker class. It works fine, yet I have a bad feeling about showing an error message dialog in try-catch block. Can it pote

Answer 1

The right way to do it is as follows:

SwingWorker worker = new SwingWorker() {
    // Executed in background thread
    protected Void doInBackground() throws Exception {
        DoFancyStuff();
        return null;
    }

    // Executed in EDT
    protected void done() {
        try {
            System.out.println("Done");
            get();
        } catch (ExecutionException e) {
            e.getCause().printStackTrace();
            String msg = String.format("Unexpected problem: %s", 
                           e.getCause().toString());
            JOptionPane.showMessageDialog(Utils.getActiveFrame(),
                msg, "Error", JOptionPane.ERROR_MESSAGE, errorIcon);
        } catch (InterruptedException e) {
            // Process e here
        }
    }
}

You should NOT try to catch exceptions in the background thread but rather let them pass through to the SwingWorker itself, and then you can get them in the done() method by calling get()which normally returns the result of doInBackground() (Voidin your situation). If an exceptionwas thrown in the background thread then get() will throw it, wrapped inside an ExecutionException.

Please also note that overidden SwingWorker methods are protected and you don't need to make them public.