catch语句中函数的错误处理

Question

This is a piece of code that I was wondering if it should be refactored to make it more complied with the Clean Code practices.

This is a class which is responsible for refunding some orders made by customers.

class RefundServiceInvoker {

    private $_orders;

    public function refundOrder() {   
        $this->getOrdersFromDB(); //This function gets all orders from DB and sets $_orders
        foreach ($this->_orders as $order) { 
            try {
                $order->refund(); //Some lines may throw an exception when refunded due to some business logic (ex. the order was already shipped)
                $this->updateOrderStatus('refunded')            
            } catch (Exception $e) {                   
                $this->logError($e);
                $this->sendMailToAdmin();
            }
        }
    }
}

of course this code is highly simplified than my original code.

My main problem is if $order->refund(); throws an exception it will be caught and logged to DB then a mail is sent. However what if $this->logError($e); itself throws an exception? or what if the mail server was down and an exception was thrown?

Better what if the DB was down itself and $this->getOrdersFromDB(); throws an exception?

My first solution was to wrap everything in one big try{}catch{}:

public function refundOrder() {   
            try {              
            $this->getOrdersFromDB(); //This function gets all orders from DB and sets $_orders
            foreach ($this->_orders as $order) { 

                    $order->refund(); //Some lines may throw an exception when refunded due to some business logic (ex. the order was already shipped)
                    $this->updateOrderStatus('refunded')            
                } catch (Exception $e) {                   
                    $this->logError($e);
                    $this->sendMailToAdmin();
                }
            }
        }

But that would mean if one order fails then all fails!! Should I put 2 try{}catch{} one for the whole function and the other for each order? But in this case too the functions in the catch might throw an exception that won't be caught.

Note:

The application is built using Zend framework 1.11.11.

Thanks in advance.

Answer 1

If you need to log and mail every exception, then you need something like this:

class RefundServiceInvoker {

   private $_orders;

   public function refundOrder() {
      try {
         $this->getOrdersFromDB();
         foreach ($this->_orders as $order) {
            try {
               $order->refund();
            } catch (MyBusinessException $e) {
               # deals with the problematic $order without stopping the loop
               $this->logError($e);
               $this->sendMailToAdmin();
            }
            $this->updateOrderStatus('refunded');
         }
      } catch(Exception $e) {
         # deals with unexpected bugs
         $this->logError($e);
         $this->sendMailToAdmin();
      }
   }
}

But you have to put a try/catch inside log and mail methods to prevent them to throw any exception when servers are offline, for example. If you don’t, the $orders loop will be stopped when log/mail fails.

If you need to log/mail only your business exception in refund() method, then you need something like this:

class RefundServiceInvoker {

   private $_orders;

   public function refundOrder() {
      $this->getOrdersFromDB();
      foreach ($this->_orders as $order) {
         try {
            $order->refund();
         } catch (MyBusinessException $e) {
            # deals with the problematic $order without stopping the loop
            $this->logError($e);
            $this->sendMailToAdmin();
         }
         $this->updateOrderStatus('refunded');
      }
   }
}

Any other exception will lead to an http 500 – internal server error page, which is usually what you want, because it’s an unexpected bug.

There’re other ways to handle this, but as you see, it depends on your needs.