EU VAT validation in Java

import java.net.URI;
import java.net.http.*;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.Map;

// Requires Java 11+ and jackson-databind
public class VATValidator {

  static final HttpClient client = HttpClient.newHttpClient();
  static final ObjectMapper mapper = new ObjectMapper();

  @SuppressWarnings("unchecked")
  public static Map<String, Object> validateVAT(
      String country, String vatNumber) throws Exception {

    var request = HttpRequest.newBuilder()
        .uri(URI.create("http://localhost:3000/api/v1/validate/" + country + "/" + vatNumber))
        .header("Authorization", "Bearer " + System.getenv("TAXID_API_KEY"))
        .GET()
        .build();

    var response = client.send(request, HttpResponse.BodyHandlers.ofString());
    return mapper.readValue(response.body(), Map.class);
  }

  public static void main(String[] args) throws Exception {
    var result = validateVAT("DE", "DE123456789");

    if (Boolean.TRUE.equals(result.get("valid"))) {
      System.out.println("Valid EU business: " + result.get("company_name"));
    } else if ("service_unavailable".equals(result.get("status"))) {
      System.out.println("VIES unavailable — retry later");
    } else {
      System.out.println("Invalid VAT number");
    }
  }
}

curl "http://localhost:3000/api/v1/validate/DE/DE123456789" \
  -H "Authorization: Bearer $TAXID_API_KEY"

# {
#   "valid": true,
#   "status": "active",
#   "company_name": "Example GmbH",
#   "company_address": "Musterstraße 1, 10115 Berlin",
#   "cached": false
# }