class SaveButton implements MagentoFrameworkViewElementUiComponentControlButtonProviderInterface {

public function __construct(
    MagentoBackendBlockWidgetContext $context,
    MagentoFrameworkUrlInterface $urlInterface,
    MagentoFrameworkAppRequestInterface $request
) {
    $this->urlBuilder = $context->getUrlBuilder();
    $this->urlInterface = $urlInterface;
    $this->request = $request;
}

public function getButtonData()
{

    $productId = $this->request->getParam('id');

    return [
        'label' => __('Save'),
        'class' => 'save primary',
         'data_attribute' => [
             'mage-init' => ['button' => ['event' => 'save']],
             'form-role' => 'save',
         ],
        'onclick' => $this->urlBuilder->getUrl( '{moduleName}/{controllerName}/save','product_id' => $productId ] ),
        'sort_order' => 90,
    ];
}