小白求助，安装adminlte后把layout和site复制到后台目录出现错误 [ 新手入门 ]

exception 'yii\base\InvalidConfigException' with message 'User::identityClass must be set.' in D:\WWW\yii2\vendor\yiisoft\yii2\web\User.php:163 Stack trace: #0 D:\WWW\yii2\vendor\yiisoft\yii2\base\Object.php(107): yii\web\User->init() #1 [internal function]: yii\base\Object->__construct(Array) #2 D:\WWW\yii2\vendor\yiisoft\yii2\di\Container.php(373): ReflectionClass->newInstanceArgs(Array) #3 D:\WWW\yii2\vendor\yiisoft\yii2\di\Container.php(154): yii\di\Container->build('yii\\web\\User', Array, Array) #4 D:\WWW\yii2\vendor\yiisoft\yii2\BaseYii.php(344): yii\di\Container->get('yii\\web\\User', Array, Array) #5 D:\WWW\yii2\vendor\yiisoft\yii2\di\ServiceLocator.php(133): yii\BaseYii::createObject(Array) #6 D:\WWW\yii2\vendor\yiisoft\yii2\di\Instance.php(155): yii\di\ServiceLocator->get('user') #7 D:\WWW\yii2\vendor\yiisoft\yii2\di\Instance.php(131): yii\di\Instance->get(NULL) #8 D:\WWW\yii2\vendor\yiisoft\yii2\filters\AccessControl.php(98): yii\di\Instance::ensure('user', 'yii\\web\\User') #9 D:\WWW\yii2\vendor\yiisoft\yii2\base\Object.php(107): yii\filters\AccessControl->init() #10 [internal function]: yii\base\Object->__construct(Array) #11 D:\WWW\yii2\vendor\yiisoft\yii2\di\Container.php(379): ReflectionClass->newInstanceArgs(Array) #12 D:\WWW\yii2\vendor\yiisoft\yii2\di\Container.php(154): yii\di\Container->build('yii\\filters\\Acc...', Array, Array) #13 D:\WWW\yii2\vendor\yiisoft\yii2\BaseYii.php(344): yii\di\Container->get('yii\\filters\\Acc...', Array, Array) #14 D:\WWW\yii2\vendor\yiisoft\yii2\base\Component.php(662): yii\BaseYii::createObject(Array) #15 D:\WWW\yii2\vendor\yiisoft\yii2\base\Component.php(646): yii\base\Component->attachBehaviorInternal('access', Array) #16 D:\WWW\yii2\vendor\yiisoft\yii2\base\Component.php(528): yii\base\Component->ensureBehaviors() #17 D:\WWW\yii2\vendor\yiisoft\yii2\base\Controller.php(269): yii\base\Component->trigger('beforeAction', Object(yii\base\ActionEvent)) #18 D:\WWW\yii2\vendor\yiisoft\yii2\web\Controller.php(108): yii\base\Controller->beforeAction(Object(yii\base\InlineAction)) #19 D:\WWW\yii2\vendor\yiisoft\yii2\base\Controller.php(152): yii\web\Controller->beforeAction(Object(yii\base\InlineAction)) #20 D:\WWW\yii2\vendor\yiisoft\yii2\base\Module.php(454): yii\base\Controller->runAction('', Array) #21 D:\WWW\yii2\vendor\yiisoft\yii2\web\Application.php(100): yii\base\Module->runAction('', Array) #22 D:\WWW\yii2\vendor\yiisoft\yii2\base\Application.php(375): yii\web\Application->handleRequest(Object(yii\web\Request)) #23 D:\WWW\yii2\backend\web\index.php(17): yii\base\Application->run() #24 {main} 报错的log,贴出来求大神看看， User::identityClass must be set. 报这个错，我把配置里user屏蔽也一样报错