SpringBoot Simple Secure API

WebSecurityFilter.java

import java.io.IOException;
import java.util.Objects;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.GenericFilterBean;

@Configuration
public class WebSecurityFilter extends GenericFilterBean {
    
    private final static String API_TOKEN_KEY = "X-Api-Token";

    private HttpServletRequest servletRequest;
    private HttpServletResponse servletResponse;
    private FilterChain filterChain;

    @Value("${app.api_token}")
    private String apiTokenProperty;

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        this.servletRequest = (HttpServletRequest) servletRequest;
        this.servletResponse = (HttpServletResponse) servletResponse;
        this.filterChain = filterChain;
        deauthorizeIncorrectApiToken();
    }

    private void deauthorizeIncorrectApiToken() throws IOException, ServletException {
        if (isValidToken()) {
            passThroughFilter();
        } else {
            sendUnauthorizedStatus();
        }
    }
    
    private boolean isValidToken() {
        return Objects.equals(getApiTokenHeader(), apiTokenProperty);
    }    

    private void passThroughFilter() throws IOException, ServletException {
        filterChain.doFilter(servletRequest, servletResponse);
    }

    private void sendUnauthorizedStatus() throws IOException {
        servletResponse.sendError(401, "Incorrect User Token");
    }
    
    private String getApiTokenHeader() {
        return servletRequest.getHeader(API_TOKEN_KEY);
    }

}