Integrate Hanko with a Java/Spring backend

import com.fasterxml.jackson.annotation.JsonProperty;
import jakarta.servlet.http.Cookie;
import jakarta.servlet.http.HttpServletRequest;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Component;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.web.client.HttpServerErrorException;
import org.springframework.web.client.RestClient;

import java.util.Arrays;
import java.util.Map;

public class HankoSessionValidationResponse {

    @JsonProperty("is_valid")
    private boolean isValid;

    public boolean isValid() {
        return isValid;
    }
}

@Component
public class HankoSessionValidator {

    private static final Logger log = LoggerFactory.getLogger(HankoSessionValidator.class);

    private final RestClient restClient;
    private final String hankoBaseUrl;
    private final String hankoCookieName;

    public HankoSessionValidator(
            @Value("${hanko.baseUrl:}") String hankoBaseUrl,
            @Value("${hanko.cookieName:hanko}") String hankoCookieName,
            RestClient.Builder restClientBuilder
    ) {
        this.hankoBaseUrl = hankoBaseUrl != null ? hankoBaseUrl.replaceAll("/+$", "") : "";
        this.hankoCookieName = hankoCookieName;
        this.restClient = restClientBuilder.build();
    }

    public boolean isSessionValid(HttpServletRequest request) {
        if (hankoBaseUrl == null || hankoBaseUrl.isBlank()) {
            log.warn("Hanko base URL is not configured");
            return false;
        }

        try {
            String token = extractSessionToken(request);
            if (token == null || token.isBlank()) {
                return false;
            }

            HankoSessionValidationResponse body = restClient.post()
                    .uri(hankoBaseUrl + "/sessions/validate")
                    .contentType(MediaType.APPLICATION_JSON)
                    .body(Map.of("session_token", token))
                    .retrieve()
                    .body(HankoSessionValidationResponse.class);

            return body != null && body.isValid();
        } catch (HttpClientErrorException | HttpServerErrorException e) {
            if (e.getStatusCode().is4xxClientError()) {
                log.debug("Hanko session invalid: {}", e.getStatusCode());
            } else {
                log.warn("Hanko validation error: {}", e.getStatusCode());
            }
            return false;
        } catch (Exception e) {
            log.warn("Failed to validate Hanko session", e);
            return false;
        }
    }

    private String extractSessionToken(HttpServletRequest request) {
        // Cookie: hanko=<token> (name configurable via hanko.cookieName)
        Cookie[] cookies = request.getCookies();
        if (cookies != null) {
            return Arrays.stream(cookies)
                    .filter(c -> hankoCookieName.equals(c.getName()))
                    .map(Cookie::getValue)
                    .filter(v -> v != null && !v.isBlank())
                    .findFirst()
                    .orElse(null);
        }

        return null;
    }
}

import jakarta.servlet.FilterChain;
import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import org.springframework.http.HttpStatus;
import org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;

import java.io.IOException;

@Component
public class HankoSessionFilter extends OncePerRequestFilter {

    private final HankoSessionValidator validator;

    public HankoSessionFilter(HankoSessionValidator validator) {
        this.validator = validator;
    }

    @Override
    protected void doFilterInternal(HttpServletRequest request,
                                    HttpServletResponse response,
                                    FilterChain filterChain) throws ServletException, IOException {
        if (!validator.isSessionValid(request)) {
            response.setStatus(HttpStatus.UNAUTHORIZED.value());
            response.setContentType("application/json");
            response.getWriter().write("{\"error\":\"unauthorized\"}");
            return;
        }
        filterChain.doFilter(request, response);
    }
}

import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.List;

@Configuration
public class SecurityConfig {

    @Bean
    public FilterRegistrationBean<HankoSessionFilter> hankoSessionFilterRegistration(HankoSessionFilter filter) {
        FilterRegistrationBean<HankoSessionFilter> registration = new FilterRegistrationBean<>();
        registration.setFilter(filter);
        registration.setUrlPatterns(List.of("/secured"));
        registration.setOrder(1);
        return registration;
    }
}