public DockerImageName dockerImageName()

in tools/container-spec-helper/src/main/java/org/apache/polaris/containerspec/ContainerSpecHelper.java [96:157]
54 lines of code
14 McCabe index (conditional complexity)

  public DockerImageName dockerImageName(String explicitImageName) {
    if (explicitImageName != null) {
      return DockerImageName.parse(explicitImageName);
    }

    String dockerfile = format("Dockerfile-%s-version", name());
    URL resource = containerClass().getResource(dockerfile);
    Objects.requireNonNull(resource, dockerfile + " not found");

    String systemPropPrefix1 = "it.polaris.container." + name() + ".";
    String systemPropPrefix2 = "polaris.testing." + name() + ".";
    String envPrefix = name().toUpperCase(Locale.ROOT).replaceAll("-", "_") + "_DOCKER_";

    String explicitImage = System.getProperty(systemPropPrefix1 + "image");
    if (explicitImage == null) {
      explicitImage = System.getProperty(systemPropPrefix2 + "image");
    }
    if (explicitImage == null) {
      explicitImage = System.getenv(envPrefix + "IMAGE");
    }
    String explicitTag = System.getProperty(systemPropPrefix1 + "tag");
    if (explicitTag == null) {
      explicitTag = System.getProperty(systemPropPrefix2 + "tag");
    }
    if (explicitTag == null) {
      explicitTag = System.getenv(envPrefix + "TAG");
    }

    if (explicitImage != null && explicitTag != null) {
      return DockerImageName.parse(explicitImage + ':' + explicitTag);
    }

    try (InputStream in = resource.openConnection().getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(in, UTF_8))) {
      String fullImageName = null;
      String ln;
      while ((ln = reader.readLine()) != null) {
        ln = ln.trim();
        if (ln.startsWith("FROM ")) {
          fullImageName = ln.substring(5).trim();
          break;
        }
      }

      if (fullImageName == null) {
        throw new IllegalStateException(
            "Dockerfile " + dockerfile + " does not contain a line starting with 'FROM '");
      }

      if (explicitImage != null || explicitTag != null) {
        throw new IllegalArgumentException(
            "Must specify either BOTH, image name AND tag via system properties or environment  or omit and leave it to the default "
                + fullImageName
                + " from "
                + dockerfile);
      }

      return DockerImageName.parse(fullImageName);
    } catch (Exception e) {
      throw new RuntimeException("Failed to extract tag from " + resource, e);
    }
  }