关于Yii::$app->user->identity不能获取用户数据问题 [ 2.0 版本 ]

表单的数据是保存在User模型里，能实现登陆与退出功能.
这是动作方法

public function actionLogin()
{
    $model=new User(['scenario'=>'login']);
    if($model->load(Yii::$app->request->post())&&$model->login())
    {
        return $this->render('entry-confirm',['model'=>$model]);
    }
    else
    {
        return $this->render('login',['model'=>$model]);
    }
}

然后在User实现login方法

public function login()
{
    if(!$this->validate())
    {
        return false;
    }
    $user=Yii::$app->db->createCommand("select * from user where username=:username",[':username'=>$this->username])->queryOne();
    if($user!==null)
    {
        if($this->checkPassword($user['password']))
        {
            return Yii::$app->user->login(User::findOne(['username'=>$this->username]),$this->rememberMe ? 3600*24*7:0);
        }
        return false;
    }
    return false;

}

这里还有个问题，如果这里用$user=User::fingOne(['username'=>$this->username])获取对象
然后$user->password为null，但是获取email其它的属性能获取到。
然后用Yii::$app->user->identity->username获取数据，显示为空,var_dump(ii::$app->user->identity):

app\models\User Object
(
    [username] => 
    [password] => 
    [rememberMe] => 
    [_attributes:yii\db\BaseActiveRecord:private] => Array
        (
            [id] => 6
            [username] => raohong
            [password] => $2y$13$4LMusps.IbhCfMBikgP6nuA.kmDmOyCqoKlbiOEv08lVhVZfiTbcy
            [authkey] => -l_yYwqmHQPrrkmXSNR097TVV3s4r_VV
            [accecctoken] => 
            [email] => 724736528@qq.com
        )

    [_oldAttributes:yii\db\BaseActiveRecord:private] => Array
        (
            [id] => 6
            [username] => raohong
            [password] => $2y$13$4LMusps.IbhCfMBikgP6nuA.kmDmOyCqoKlbiOEv08lVhVZfiTbcy
            [authkey] => -l_yYwqmHQPrrkmXSNR097TVV3s4r_VV
            [accecctoken] => 
            [email] => 724736528@qq.com
        )

    [_related:yii\db\BaseActiveRecord:private] => Array
        (
        )

    [_errors:yii\base\Model:private] => 
    [_validators:yii\base\Model:private] => 
    [_scenario:yii\base\Model:private] => default
    [_events:yii\base\Component:private] => Array
        (
        )

    [_behaviors:yii\base\Component:private] => Array
        (
        )

)

有点奇怪,求解