Log Java NullPointerException stack trace

At Spring Boot Whenever a bad Nullpo (the one who made the bug is really bad) comes out, I'm in trouble because I can't keep up with it, so I decided to attach a handler that issues a stack trace to the bottom of the Controller. Surprisingly useful for debugging.

@ExceptionHandler({NullPointerException.class})
public String handleRunTimeException(NullPointerException ex) throws IOException {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw);
    ex.printStackTrace(pw);
    String stackTraceString = sw.toString();
    log.error(stackTraceString);
    sw.close();
    pw.close();
    return "redirect:error/500";
}