如何在yii2中保存json格式的模型？

use yii\db\ActiveRecord;
use yii\helpers\Json;

class MyModel extends ActiveRecord
{
    /**
     * @var string JSON数据
     */
    public $jsonData;

    public function rules()
    {
        return [
            ['jsonData', 'string'],
            ['jsonData', 'validateJson'],
        ];
    }

    public function validateJson($attribute, $params)
    {
        if (!Json::decode($this->$attribute)) {
            $this->addError($attribute, 'Invalid JSON format.');
        }
    }

    public function beforeSave($insert)
    {
        if (parent::beforeSave($insert)) {
            $this->jsonData = Json::encode($this->jsonData);
            return true;
        }
        return false;
    }
}

$model = new MyModel();
$model->jsonData = '{"name": "John", "age": 30}';

if ($model->save()) {
    echo 'JSON data saved successfully.';
} else {
    echo 'Failed to save JSON data.';
}