アクセストークンの生成

POST /api/data HTTP/1.1
Host: example.com
Authorization: Bearer eyJhbGciOiJIUzI1...

import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class AccessTokenService {
    private static final Logger logger = LoggerFactory.getLogger(AccessTokenService.class);

    public String getAccessToken() {
        ClassLoader classLoader = AccessTokenService.class.getClassLoader();

        try (InputStream inputStream = classLoader.getResourceAsStream("credentials/server_credentials.json")) {
            if (inputStream == null) {
                logger.error("File not found: credentials/server_credentials.json");
                throw new IllegalArgumentException("Missing credentials file");
            }

            try (InputStreamReader reader = new InputStreamReader(inputStream, StandardCharsets.UTF_8);
                 CloseableHttpClient httpClient = HttpClients.createDefault()) {

                JsonObject jsonObject = JsonParser.parseReader(reader).getAsJsonObject();
                String clientId = jsonObject.get("clientId").getAsString();
                String clientSecret = jsonObject.get("clientSecret").getAsString();
                String adobeIMSV3TokenEndpointURL = jsonObject.get("adobeIMSV3TokenEndpointURL").getAsString();
                String scopes = jsonObject.get("scopes").getAsString();

                HttpPost request = new HttpPost(adobeIMSV3TokenEndpointURL);
                request.setHeader("Content-Type", "application/x-www-form-urlencoded");

                String requestBody = "grant_type=client_credentials&client_id=" + clientId +
                        "&client_secret=" + clientSecret +
                        "&scope=" + scopes;

                request.setEntity(new StringEntity(requestBody, ContentType.APPLICATION_FORM_URLENCODED));

                logger.info("Requesting access token from {}", adobeIMSV3TokenEndpointURL);

                try (CloseableHttpResponse response = httpClient.execute(request)) {
                    String responseString = EntityUtils.toString(response.getEntity());
                    JsonObject jsonResponse = JsonParser.parseString(responseString).getAsJsonObject();

                    if (!jsonResponse.has("access_token")) {
                        logger.error("Access token not found in response: {}", responseString);
                        return null;
                    }

                    String accessToken = jsonResponse.get("access_token").getAsString();
                    logger.info("Successfully obtained access token.");
                    return accessToken;
                }
            }
        } catch (Exception e) {
            logger.error("Error fetching access token", e);
        }
        return null;
    }
}