Error Handling in ASP, Part 2 - 4GuysFromRolla.com

Error Handling in ASP, Part 2

- continued -

The question now is how to we "trap" errors? Well, after any ADO call that accesses the database, we will want to put the following lines:


If Err.number <> 0 then
  TrapError Err.description
End If

You will want to put this after all ADO calls that communicate directly with the database. This includes ConnectionObject.Open, ConnectionObject.Execute, and RecordsetObject.Open. Now, you may be wondering where the sub TrapError is defined: we're about to do that. Create a file called ErrorHandler.asp and put it in your /include or /scripts directory. In ErrorHandler.asp, we will have the following subs:

TrapError ProcessErrors

Let's look at the code for ErrorHandler.asp:


<%
Dim strErrorMessage
Dim bolErrors

'Initialize variables
strErrorMessage = ""	'The error messages for tech. support
bolErrors = False	'Have we found any errors yet?

'Now our two subs
sub TrapError(strError)
  bolErrors = True	'Egad, we've found an error!

  strErrorMessage = strErrorMessage & strError & ", "
end sub



'If there are any errors, this function will email tech. support
sub ProcessErrors()
  if bolErrors then
    'Send the email
    Dim objCDO
    Set objCDO = Server.CreateObject("CDONTS.NewMail")

    objCDO.To = "techsupport@mysite.com"
    objCDO.From = "techsupport@mysite.com"
    objCDO.Subject = "AN ADO ERROR OCCURRED"
    objCDO.Body = "At " & Now & " the following errors occurred on " & _
		  "the page " & Request.ServerVariables("SCRIPT_NAME") & _
		  ": " & _
                  chr(10) & chr(10) & strErrorMessage

    objCDO.Send

    Set objCDO = Nothing

    'Now, we've got to print out something for the user
    Response.Write "There has been a database error.  Technical Support " & _
                   "has already been notified.  You will be informed when " & _
                   "this issue is resolved.  Thank you for your patience!"
  end if
end sub

That's all there is to it! Of course, you need to have the SMTP piece installed on your webserver. (See this article for more information on sending email using CDO.). Now, at the top of all your pages that you want to use the error handling routines, you'll need to include ErrorHandler.asp like so:

(See this article for more information on using includes.) You also need to make a call to the ProcessErrors sub at the end of all your ASP scripts which use this Error Trapping. So, the last line in the ASP file would be <% ProcessErrors %>. It is also imperative that you have On Error Resume Next at the top of all these pages as well!

Well, hopefully that wasn't too difficult to follow! Error handling allows you to cope with error messages in a more pleasant way for the end user. Furthermore, it helps with debugging. User's accounts of errors are usually quite different than the actual error messages! With this approach, however, you're technical support department will receive the actual error messages! Neat, eh? (Oh yeah, one other benefit. I had implemented a system like this at my first internship. Folks would usually email me after an error occurred, but due to this email notification, I'd be to their office before they finished writing the email to me.)

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