API Screenshot en Java : exemple de bout en bout

Java 11+ côté serveur

java.net.http.HttpClient gère TLS 1.2+, les timeouts et le streaming sans Apache HttpClient. Gson reste l’option la plus légère pour parser l’enveloppe { success, data }. Pour un client supporté, préférez le SDK Java. Référence des paramètres : Developers.

Classe complète (messages en français)

import java.io.IOException;
import java.net.URI;
import java.net.URLEncoder;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.time.Duration;
import java.util.Map;
import java.util.StringJoiner;
import com.google.gson.Gson;
import com.google.gson.JsonObject;

public final class CaptureEcran {
  private static final String BASE = "https://api.screenshotcenter.com/api/v1";
  private static final Gson GSON = new Gson();

  public static void main(String[] args) throws Exception {
    String cle = System.getenv("SCREENSHOTCENTER_API_KEY");
    if (cle == null || cle.isBlank()) {
      System.err.println("Définissez SCREENSHOTCENTER_API_KEY");
      System.exit(1);
    }
    String page = args.length > 0 ? args[0] : "https://example.com";
    HttpClient client = HttpClient.newBuilder().connectTimeout(Duration.ofSeconds(30)).build();
    long id = creer(client, cle, page);
    System.out.println("Identifiant de capture : " + id);
    attendreTermine(client, cle, id, Duration.ofSeconds(2), Duration.ofMinutes(5));
    Path fichier = Path.of("screenshot.png");
    telechargerVignette(client, cle, id, fichier);
    System.out.println("Fichier écrit : " + fichier.toAbsolutePath());
  }

  private static String enc(Map<String, String> p) {
    StringJoiner j = new StringJoiner("&");
    for (var e : p.entrySet()) {
      j.add(
          URLEncoder.encode(e.getKey(), StandardCharsets.UTF_8)
              + "="
              + URLEncoder.encode(e.getValue(), StandardCharsets.UTF_8));
    }
    return j.toString();
  }

  private static JsonObject getJson(HttpClient c, String url) throws Exception {
    var req = HttpRequest.newBuilder(URI.create(url)).GET().timeout(Duration.ofMinutes(2)).build();
    HttpResponse<String> resp = c.send(req, HttpResponse.BodyHandlers.ofString());
    if (resp.statusCode() != 200) {
      throw new IOException("HTTP " + resp.statusCode() + " : " + resp.body());
    }
    JsonObject racine = GSON.fromJson(resp.body(), JsonObject.class);
    if (!racine.get("success").getAsBoolean()) {
      throw new IOException("Erreur API : " + resp.body());
    }
    return racine.getAsJsonObject("data");
  }

  private static long creer(HttpClient c, String cle, String page) throws Exception {
    String q = enc(Map.of("key", cle, "url", page, "country", "us"));
    return getJson(c, BASE + "/screenshot/create?" + q).get("id").getAsLong();
  }

  private static JsonObject info(HttpClient c, String cle, long id) throws Exception {
    return getJson(c, BASE + "/screenshot/info?" + enc(Map.of("key", cle, "id", Long.toString(id))));
  }

  private static void attendreTermine(HttpClient c, String cle, long id, Duration poll, Duration max)
      throws Exception {
    long limite = System.nanoTime() + max.toNanos();
    while (System.nanoTime() < limite) {
      String st = info(c, cle, id).get("status").getAsString();
      if ("finished".equals(st)) {
        return;
      }
      if ("error".equals(st)) {
        throw new IOException("La capture a échoué côté API");
      }
      Thread.sleep(poll.toMillis());
    }
    throw new IOException("Délai dépassé pour la capture " + id);
  }

  private static void telechargerVignette(HttpClient c, String cle, long id, Path dest) throws Exception {
    String q = enc(Map.of("key", cle, "id", Long.toString(id)));
    var req =
        HttpRequest.newBuilder(URI.create(BASE + "/screenshot/thumbnail?" + q))
            .GET()
            .timeout(Duration.ofMinutes(2))
            .build();
    HttpResponse<byte[]> resp = c.send(req, HttpResponse.BodyHandlers.ofByteArray());
    if (resp.statusCode() != 200) {
      throw new IOException("Téléchargement HTTP " + resp.statusCode());
    }
    Files.write(dest, resp.body());
  }
}

Maven

<dependency>
  <groupId>com.google.code.gson</groupId>
  <artifactId>gson</artifactId>
  <version>2.11.0</version>
</dependency>