Question

The standard logging code does not seem to work instantiating a logger with the canonical name nor using an anonymous logger.

Code below:

private static final Logger logger = Logger.getLogger(UserAccessFilter.class
  .getCanonicalName());

// ...
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain)
  throws IOException, ServletException {
  if (!UsersHelper.isValid(req)) {
    logger.log(Level.WARNING, getErrorMessage(req));
    // ... some error serving code
  } else {
    chain.doFilter(req, resp);
  }
}

Answer 1

Yes, you can log from a servlet filter – I’m doing it in my code.

I bet you are logging at info levels, while App Engine only reports warning and above by default. Look in WEB-INF/logging.properties and add / replace .level = INFO to see INFO messages (or log WARNING+ messages).