Zend auth checking

 public function authAction()  
   {  
     $request   = $this->getRequest();  
     $registry   = Zend_Registry::getInstance();  
     $auth    = Zend_Auth::getInstance();  
     $DB = Zend_Db_Table::getDefaultAdapter();  
     $authAdapter = new Zend_Auth_Adapter_DbTable($DB);  
     $authAdapter->setTableName('user')  
           ->setIdentityColumn('user_name')  
           ->setCredentialColumn('password');    
     // Set the input credential values  
     $uname = $request->getParam('user_name');  
     $paswd = $request->getParam('password');  
     $authAdapter->setIdentity($uname);  
     $authAdapter->setCredential(md5($paswd));  
     // Perform the authentication query, saving the result  
     $result = $auth->authenticate($authAdapter);  
     if($result->isValid())  
     {  
       $data = $authAdapter->getResultRowObject(null,'password');  
       $auth->getStorage()->write($data);  
       $this->_redirect('user/index/listuser');  
     }  
     else  
     {  
       $this->_flashMessenger->addMessage($this->view->translator('user_invalid_login'));  
       $this->_redirect('user/index/login');  
     }  
   }