Custom error handling in Textarea

I have code like that:

formulaArea = new TextArea("Insert text here");                                           
formulaArea.addValidator(new StringLengthValidator("Text is too long!", 0, 400, false));  
formulaArea.addTextChangeListener(new FieldEvents.TextChangeListener() {                  
    @Override                                                                                
    public void textChange(FieldEvents.TextChangeEvent textChangeEvent) {                    
        counter.setValue(String.format(COUNTER_PATH, textChangeEvent.getText().length()));      
    }                                                                                        
});                                                                                       
formulaArea.setErrorHandler(new NotificationErrorHandler());                              
formulaArea.setImmediate(true);                                                           

At line 9 added custom ErrorHandler that show notification (it works fine).
Test case:

when

  • write text longer than maximum number of chars, here 400
  • click outside the text area (leave it)
    then
  • notification appear - nope, nope, nopeā€¦

Notifications does not appeared but only standard error indicator near by field description appear.

My question is, how to prepare custom error handling in this case? I would like to show notification not just that small exclamation mark near by field description.