WebhookServer.java

/*
 * A webhook receiver on the JDK's own HTTP server — no framework.
 *
 * export VISION_WEBHOOK_SECRET=whsec_… # dashboard → Webhooks
 * java -cp target/visionapi-java-1.0.0.jar examples/WebhookServer.java
 *
 * The endpoint must be HTTPS and must not resolve to a private address, so a bare localhost
 * receiver is unreachable by design — put a tunnel (ngrok, cloudflared) in front of it while
 * developing.
 */

import com.sun.net.httpserver.HttpServer;
import io.visionapi.Webhook;
import io.visionapi.WebhookSignatureException;
import java.io.IOException;
import java.net.InetSocketAddress;

public class WebhookServer {

 public static void main(String[] args) throws IOException {
 String secret = System.getenv("VISION_WEBHOOK_SECRET");
 if (secret == null || secret.isBlank()) {
 System.err.println("Set VISION_WEBHOOK_SECRET (dashboard → Webhooks).");
 System.exit(1);
 }

 HttpServer server = HttpServer.create(new InetSocketAddress(3000), 0);
 server.createContext("/hooks/vision", exchange -> {
 if (!"POST".equals(exchange.getRequestMethod())) {
 exchange.sendResponseHeaders(405, -1);
 exchange.close();
 return;
 }

 // Read the raw bytes. The signature covers exactly what arrived — decoding first
 // and re-encoding changes key order and whitespace, and the HMAC stops matching.
 byte[] body = exchange.getRequestBody().readAllBytes();

 Webhook.Event event;
 try {
 event = Webhook.verify(body, exchange.getRequestHeaders().getFirst("X-Vision-Signature"), secret);
 } catch (WebhookSignatureException e) {
 System.err.println("rejected delivery: " + e.getMessage());
 exchange.sendResponseHeaders(400, -1);
 exchange.close();
 return;
 }

 // Any 2xx is success. Acknowledge immediately and do the work afterwards — a slow
 // handler looks like a failed delivery and earns a retry at +1 m, +5 m, +15 m, +40 m.
 exchange.sendResponseHeaders(202, -1);
 exchange.close();

 if (event.isFailure()) {
 System.err.println("task " + event.taskId() + " failed: "
 + event.error().map(e -> e.get("code")).orElse("unknown"));
 } else {
 System.out.println("task " + event.taskId() + " completed — "
 + event.creditsUsed() + " credits");
 System.out.println(event.result().unwrap(true));
 }
 });

 server.start();
 System.out.println("listening on http://localhost:3000/hooks/vision");
 }
}