Its weird, sometimes doFilter() is called once twice, once with ‘Authorization’ as null and then with actual ‘Authorization’ token. I am calling spring boot rest controller from a react fetch call.

react fetch call with headers:

const handleSubmit = (e) => {
    if (validateForm()) {
        const token = localStorage.getItem('token');
        setIsLoading(true);

        const headerList = {
            'Authorization': 'Bearer ' + token
        }

        e.preventDefault();
        const city = { cityName, cityDescription, stateId };

        fetch(API_HOST_URL + "/cities/", {
            method: "POST",
            headers: headerList,
            body: JSON.stringify(city)
        }).then((res) => {
            onSuccessfulSave();
            resetForm();
        }).catch((error) => {
            onFailedSave();
        });
    }
    else {
        onFailedSave();
    }
}

Here is the filter code:

@Component
public class RequestFilter implements Filter {

    private final JwtService jwtService;

    public RequestFilter(JwtService jwtService) {
        this.jwtService = jwtService;
    }

    @Override
    public void doFilter(
            ServletRequest request,
            ServletResponse response,
            FilterChain chain) throws ServletException, IOException {

        HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse res = (HttpServletResponse) response;
        System.out.println("Request path: " + req.getRequestURI());
        System.out.println("Authorization: " + req.getHeader("Authorization"));
        chain.doFilter(request, response);
    }
}

Why sometimes only doFilter is called twice and why sometimes it pass ‘Authorization’ header and sometimes not?