Since he's writing Java, I would rewrite his initial function:

    public int getIntFromHeader(Request req, String headerName) {
        if(req != null && req.getHeaders() != null) {
            String header = req.getHeaders().get(headerName);
            if(header != null) {
                try {
                    return Integer.parseInt(header);
                } catch(Exception e) {
                   return -1;
                }
            }
        }
        return -1;
    }

as

    public int getIntFromHeader(Request req, String headerName) {
        return Integer.parseInt(req.getHeaders().get(headerName));
    }

That way it either returns with a valid int or throws an exception of some sort (null or otherwise).

Also, -1 is a perfectly valid integer and so this function can't distinguish between a header with -1 in it and an error. The fact that there's a req != null check seems silly. Surely, the caller should be responsible for that and if they aren't they should get an exception.