Design question - how atomic should a business layer method be?

Question

This issue is technology agnostic, but I am working with C# and ASP.NET and will use this for the pseudo code. Which is the better approach, and why?

Encapsulate logging, transaction and exception handling:

protected void Page_Load(object sender, EventArgs e) {
 SomeBusinessClass.SomeBusinessMethod();
}


public class SomeBusinessClass {
  public void SomeBusinessMethod() {
    using (TransactionScope ts = new TransactionScope()) {
                doStuff();
                ts.Complete();
            }
            catch (Exception ex) {
                LogError("An error occured while saving the order", ex);
            }
        }
    }
}

Delegate logging, transaction and exception handling to the caller:

protected void Page_Load(object sender, EventArgs e) {
    using (TransactionScope ts = new TransactionScope()) {
          try {
                SomeBusinessClass.SomeBusinessMethod();
                ts.Complete();
          }
          catch (Exception ex) {
                LogError("An error occured while saving the order", ex);
          }
     }
}


public class SomeBusinessClass {
  public void SomeBusinessMethod() {
      doStuff();
    }
}

I am concerned that by introducing dependencies on logging, transactions, etc in my business logic code, I make it less generic. On the other hand, the UI code looks so much cleaner. I can't make the call. Let me know what other factors I should consider.

I prefer Number 1. My reason is if the code has to be wrapped in a Transaction then the client who is going to call my code may or may not wrap it in a transaction. Also, the UI part looks much cleaner. I do have some way of letting the user know if something failed by not returning void. — iJK, Nov 19 '09 at 18:04

score 5 · Accepted Answer · edited May 23 '17 at 12:01

Transactions: a central concern of your business layer, so it should absolutely handle this (though you might centralize transaction handling via a unit of work implementation).

Update: I don't agree with this part any more. Often, the controller, presenter, or or another top-level caller is the best place to handle transactions (a la the the onion architecture) - in many cases, that's where the logical unit of work is defined.

Exception Handling: use as needed in every layer - but only use it in the business layer when you can actually do something about it (not just log it). Use a global handler in the UI layer if your infrastructure supports one.

Logging: use trace or informational logging in whatever layers need it, only log exceptions in the top layer.

score 2 · Answer 2 · answered Nov 19 '09 at 18:23

Use Inversion of Control:

protected void Page_Load(object sender, EventArgs e) {
 new SomeBusinessClass(_logger, _dbcontext, _exceptionhandler).SomeBusinessMethod();
}

A better one would be

protected void Page_Load(object sender, EventArgs e) {
  _mybusinessclass.SomeBusinessMethod();
}

where _mybusiness class is passed to your page via IoC container, along with populated _logger, _dbcontext, and _exceptionhandler. If you need to create _exceptionhandler manually, for example "new RedirectExceptionHandler(this)", then

protected void Page_Load(object sender, EventArgs e) {
  _mybusinessclass.SomeBusinessMethod(new RedirectExceptionHandler(this));
}

Now it really boils down to your specific design decisions. Don't know how to do IoC in ASP.NET, though, since I use MVC.

Another option is to use Aspect Oriented Programming to catch exceptions and do logging. Yet another option (available in www.sharparchitecture.net) is to handle transactions declaratively using [Transaction] attributes on method.

score 1 · Answer 3 · answered Nov 19 '09 at 17:58

1

Anything that makes the UI thinner will make your life easier.

answered Nov 19 '09 at 17:58

Robert Harvey

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Yup, yup. As long as it's in one place instead of living in every place it's called; the rest is academic. – Sonny Boy Nov 19 '09 at 18:02

Design question - how atomic should a business layer method be?

3 Answers3