public String getExternalId() {
        return this.externalId;
    }
<p>
The external ID (if any) provided in the <a
href="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_CreateAssetModel.html"
>CreateAssetModel</a> or <a
href="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_UpdateAssetModel.html"
>UpdateAssetModel</a> operation. You can assign an external ID by specifying this value as part of a call to <a
href
="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_UpdateAssetModel.html">UpdateAssetModel</a>.
However, you can't change the external ID if one is already assigned. For more information, see <a
href="https://docs.aws.amazon.com/iot-sitewise/latest/userguide/object-ids.html#external-ids">Using external
IDs</a> in the <i>IoT SiteWise User Guide</i>.
</p>

@return The external ID (if any) provided in the <a
        href="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_CreateAssetModel.html"
        >CreateAssetModel</a> or <a
        href="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_UpdateAssetModel.html"
        >UpdateAssetModel</a> operation. You can assign an external ID by specifying this value as part of a call
        to <a href="https://docs.aws.amazon.com/iot-sitewise/latest/APIReference/API_UpdateAssetModel.html">
        UpdateAssetModel</a>. However, you can't change the external ID if one is already assigned. For more
        information, see <a
        href="https://docs.aws.amazon.com/iot-sitewise/latest/userguide/object-ids.html#external-ids">Using
        external IDs</a> in the <i>IoT SiteWise User Guide</i>.
aws-java-sdk-iotsitewise/src/main/java/com/amazonaws/services/iotsitewise/model/AssetModelProperty.java