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

Yii::$app->user->identity->username获取数据，显示为空,var_dump(ii::$app->user->identity)

common\models\register\LoginUser Object
(

[username] => 
[password] => 
[rememberMe] => 1
[_user:common\models\register\LoginUser:private] => 
[_attributes:yii\db\BaseActiveRecord:private] => Array
    (
        [id] => 1
        [username] => xiaoqiang
        [password] => 
        [phone] => 18094570201
        [ip] => 
        [status] => 10
        [password_hash] => $2y$13$MPXhbqGADeuHLI6L.ld0vOy6KNoP0MDMty/8qUZf5kY.oh0X0Rqk2
        [auth_key] => 
        [created] => 0000-00-00 00:00:00
    )

[_oldAttributes:yii\db\BaseActiveRecord:private] => Array
    (
        [id] => 1
        [username] => xiaoqiang
        [password] => 
        [phone] => 18094570201
        [ip] => 
        [status] => 10
        [password_hash] => $2y$13$MPXhbqGADeuHLI6L.ld0vOy6KNoP0MDMty/8qUZf5kY.oh0X0Rqk2
        [auth_key] => 
        [created] => 0000-00-00 00:00:00
    )

[_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
    (
    )

)