@java.lang.Override
    public java.lang.String getCredentialsSecret() {
      java.lang.Object ref = credentialsSecret_;
      if (ref instanceof java.lang.String) {
        return (java.lang.String) ref;
      } else {
        com.google.protobuf.ByteString bs = (com.google.protobuf.ByteString) ref;
        java.lang.String s = bs.toStringUtf8();
        credentialsSecret_ = s;
        return s;
      }
    }
<pre>
Optional. The Resource name of a secret in Secret Manager.

AWS credentials must be stored in Secret Manager in JSON format:

{
 "access_key_id": "ACCESS_KEY_ID",
 "secret_access_key": "SECRET_ACCESS_KEY"
}

[GoogleServiceAccount][google.storagetransfer.v1.GoogleServiceAccount] must
be granted `roles/secretmanager.secretAccessor` for the resource.

See [Configure access to a source: Amazon S3]
(https://cloud.google.com/storage-transfer/docs/source-amazon-s3#secret_manager)
for more information.

If `credentials_secret` is specified, do not specify
[role_arn][google.storagetransfer.v1.AwsS3Data.role_arn] or
[aws_access_key][google.storagetransfer.v1.AwsS3Data.aws_access_key].

Format: `projects/{project_number}/secrets/{secret_name}`
</pre>

<code>string credentials_secret = 7 [(.google.api.field_behavior) = OPTIONAL];</code>

@return The credentialsSecret.
java-storage-transfer/proto-google-cloud-storage-transfer-v1/src/main/java/com/google/storagetransfer/v1/proto/TransferTypes.java