How to use com.google.auth.http

final HttpRequestInitializer delegate =
  scopedCredentials != null && scopedCredentials != NoCredentials.getInstance()
    ? new HttpCredentialsAdapter(scopedCredentials)
    : null;
HeaderProvider internalHeaderProvider =

/** Constructs an instance of this rpc client with provided {@link DnsOptions}. */
public HttpDnsRpc(DnsOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 this.dns =
   new Dns.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
 this.options = options;
}

 @Override
 public void initialize(HttpRequest httpRequest) throws IOException {
  credentialsAdapter.initialize(httpRequest);
  httpRequest.setConnectTimeout(connectTimeout);
  httpRequest.setReadTimeout(readTimeout);
 }
}

private HttpRequestInitializer chainHttpRequestInitializer(Credentials credential,
    HttpRequestInitializer httpRequestInitializer) {
  if (credential == null) {
    return httpRequestInitializer;
  } else {
    return new ChainingHttpRequestInitializer(new HttpCredentialsAdapter(credential), httpRequestInitializer);
  }
}

public HttpComputeRpc(ComputeOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 this.options = options;
 compute =
   new Compute.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
}

private static HttpRequestInitializer chainHttpRequestInitializer(
  Credentials credential, HttpRequestInitializer httpRequestInitializer) {
 if (credential == null) {
  return httpRequestInitializer;
 } else {
  return new ChainingHttpRequestInitializer(
    new HttpCredentialsAdapter(credential), httpRequestInitializer);
 }
}

public HttpTranslateRpc(TranslateOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 this.options = options;
 translate =
   new Translate.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
}

 private static HttpRequestInitializer chainHttpRequestInitializer(
   Credentials credential, HttpRequestInitializer httpRequestInitializer) {
  if (credential == null) {
   NullCredentialInitializer.throwNullCredentialException();
  }
  return new ChainingHttpRequestInitializer(
    new HttpCredentialsAdapter(credential), httpRequestInitializer);
 }
}

public HttpBigQueryRpc(BigQueryOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 this.options = options;
 bigquery =
   new Bigquery.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
}

private static HttpRequestInitializer chainHttpRequestInitializer(
  Credentials credential, HttpRequestInitializer httpRequestInitializer) {
 if (credential == null) {
  return new ChainingHttpRequestInitializer(
    new NullCredentialInitializer(), httpRequestInitializer);
 } else {
  return new ChainingHttpRequestInitializer(
    new HttpCredentialsAdapter(credential), httpRequestInitializer);
 }
}

public HttpResourceManagerRpc(ResourceManagerOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 resourceManager =
   new CloudResourceManager.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
 clock = options.getClock();
}

 private static HttpRequestInitializer chainHttpRequestInitializer(
   Credentials credential, HttpRequestInitializer httpRequestInitializer) {
  if (credential == null) {
   return new ChainingHttpRequestInitializer(
     new NullCredentialInitializer(), httpRequestInitializer);
  } else {
   return new ChainingHttpRequestInitializer(
     new HttpCredentialsAdapter(credential), httpRequestInitializer);
  }
 }
}

public HttpDatastoreRpc(DatastoreOptions options) {
 HttpTransportOptions httpTransportOptions =
   (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = httpTransportOptions.getHttpTransportFactory().create();
 com.google.datastore.v1.client.DatastoreOptions.Builder clientBuilder =
   new com.google.datastore.v1.client.DatastoreOptions.Builder()
     .projectId(options.getProjectId())
     .initializer(getHttpRequestInitializer(options, httpTransportOptions))
     .transport(transport);
 String normalizedHost = options.getHost() != null ? options.getHost().toLowerCase() : "";
 if (isLocalHost(normalizedHost)) {
  clientBuilder = clientBuilder.localHost(removeScheme(normalizedHost));
 } else if (!removeScheme(com.google.datastore.v1.client.DatastoreFactory.DEFAULT_HOST)
     .equals(removeScheme(normalizedHost))
   && !normalizedHost.isEmpty()) {
  String fullUrl = normalizedHost;
  if (fullUrl.charAt(fullUrl.length() - 1) != '/') {
   fullUrl = fullUrl + '/';
  }
  fullUrl =
    fullUrl
      + com.google.datastore.v1.client.DatastoreFactory.VERSION
      + "/projects/"
      + options.getProjectId();
  clientBuilder = clientBuilder.projectId(null).projectEndpoint(fullUrl);
 }
 client = com.google.datastore.v1.client.DatastoreFactory.get().create(clientBuilder.build());
}

 private static HttpRequestInitializer chainHttpRequestInitializer(
   Credentials credential, HttpRequestInitializer httpRequestInitializer) {
  if (credential == null) {
   return new ChainingHttpRequestInitializer(
     new NullCredentialInitializer(), httpRequestInitializer);
  } else {
   return new ChainingHttpRequestInitializer(
     new HttpCredentialsAdapter(credential), httpRequestInitializer);
  }
 }
}

public HttpStorageRpc(StorageOptions options) {
 HttpTransportOptions transportOptions = (HttpTransportOptions) options.getTransportOptions();
 HttpTransport transport = transportOptions.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = transportOptions.getHttpRequestInitializer(options);
 this.options = options;
 // Open Census initialization
 censusHttpModule = new CensusHttpModule(tracer, true);
 initializer = censusHttpModule.getHttpRequestInitializer(initializer);
 batchRequestInitializer = censusHttpModule.getHttpRequestInitializer(null);
 HttpStorageRpcSpans.registerAllSpanNamesForCollection();
 storage =
   new Storage.Builder(transport, new JacksonFactory(), initializer)
     .setRootUrl(options.getHost())
     .setApplicationName(options.getApplicationName())
     .build();
}

 private static HttpRequestInitializer chainHttpRequestInitializer(
   Credentials credential, HttpRequestInitializer httpRequestInitializer) {
  if (credential == null) {
   return new ChainingHttpRequestInitializer(
     new NullCredentialInitializer(), httpRequestInitializer);
  } else {
   return new ChainingHttpRequestInitializer(
     new HttpCredentialsAdapter(credential), httpRequestInitializer);
  }
 }
}

public DefaultComputeRpc(ComputeOptions options) {
 HttpTransport transport = options.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = options.getHttpRequestInitializer();
 this.options = options;
 compute = new Compute.Builder(transport, new JacksonFactory(), initializer)
   .setRootUrl(options.getHost())
   .setApplicationName(options.getApplicationName())
   .build();
}

private static HttpRequestInitializer chainHttpRequestInitializer(
  Credentials credential, HttpRequestInitializer httpRequestInitializer) {
 if (credential == null) {
  return new ChainingHttpRequestInitializer(
    new NullCredentialInitializer(), httpRequestInitializer);
 } else {
  return new ChainingHttpRequestInitializer(
    new HttpCredentialsAdapter(credential), httpRequestInitializer);
 }
}

/**
 * Constructs an instance of this rpc client with provided {@link DnsOptions}.
 */
public DefaultDnsRpc(DnsOptions options) {
 HttpTransport transport = options.getHttpTransportFactory().create();
 HttpRequestInitializer initializer = options.getHttpRequestInitializer();
 this.dns = new Dns.Builder(transport, new JacksonFactory(), initializer)
   .setRootUrl(options.getHost())
   .setApplicationName(options.getApplicationName())
   .build();
 this.options = options;
}

public FirebaseRequestInitializer(FirebaseApp app) {
 GoogleCredentials credentials = ImplFirebaseTrampolines.getCredentials(app);
 this.credentialsAdapter = new HttpCredentialsAdapter(credentials);
 this.connectTimeout = app.getOptions().getConnectTimeout();
 this.readTimeout = app.getOptions().getReadTimeout();
}