@Component("restAuthenticationEntryPoint")
public class RestAuthenticationEntryPoint implements AuthenticationEntryPoint{

    public void commence(HttpServletRequest request, HttpServletResponse response, AuthenticationException authenticationException) throws IOException, ServletException {

        response.setContentType("application/json");
        response.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        response.getOutputStream().println("{ \"error\": \"" + authenticationException.getMessage() + "\" }");

    }
}