VBScript -- Using error handling
VbscriptError HandlingVbscript Problem Overview
I want to use VBScript to catch errors and log them (ie on error "log something") then resume the next line of the script.
For example,
On Error Resume Next 'Do Step 1 'Do Step 2 'Do Step 3
When an error occurs on step 1, I want it to log that error (or perform other custom functions with it) then resume at step 2. Is this possible? and how can I implement it?
EDIT: Can I do something like this?
On Error Resume myErrCatch 'Do step 1 'Do step 2 'Do step 3myErrCatch: 'log error Resume Next
Vbscript Solutions
Solution 1 - Vbscript
VBScript has no notion of throwing or catching exceptions, but the runtime provides a global Err object that contains the results of the last operation performed. You have to explicitly check whether the Err.Number property is non-zero after each operation.
On Error Resume Next
DoStep1
If Err.Number <> 0 Then
WScript.Echo "Error in DoStep1: " & Err.Description
Err.Clear
End If
DoStep2
If Err.Number <> 0 Then
WScript.Echo "Error in DoStop2:" & Err.Description
Err.Clear
End If
'If you no longer want to continue following an error after that block's completed,
'call this.
On Error Goto 0
The "On Error Goto [label]" syntax is supported by Visual Basic and Visual Basic for Applications (VBA), but VBScript doesn't support this language feature so you have to use On Error Resume Next as described above.
Solution 2 - Vbscript
Note that On Error Resume Next
is not set globally. You can put your unsafe part of code eg into a function, which will interrupted immediately if error occurs, and call this function from sub containing precedent OERN
statement.
ErrCatch()
Sub ErrCatch()
Dim Res, CurrentStep
On Error Resume Next
Res = UnSafeCode(20, CurrentStep)
MsgBox "ErrStep " & CurrentStep & vbCrLf & Err.Description
End Sub
Function UnSafeCode(Arg, ErrStep)
ErrStep = 1
UnSafeCode = 1 / (Arg - 10)
ErrStep = 2
UnSafeCode = 1 / (Arg - 20)
ErrStep = 3
UnSafeCode = 1 / (Arg - 30)
ErrStep = 0
End Function
Solution 3 - Vbscript
You can regroup your steps functions calls in a facade function :
sub facade()
call step1()
call step2()
call step3()
call step4()
call step5()
end sub
Then, let your error handling be in an upper function that calls the facade :
sub main()
On error resume next
call facade()
If Err.Number <> 0 Then
' MsgBox or whatever. You may want to display or log your error there
msgbox Err.Description
Err.Clear
End If
On Error Goto 0
end sub
Now, let's suppose step3()
raises an error. Since facade()
doesn't handle errors (there is no On error resume next
in facade()
), the error will be returned to main()
and step4()
and step5()
won't be executed.
Your error handling is now refactored in 1 code block
Solution 4 - Vbscript
I'm exceptionally new to VBScript, so this may not be considered best practice or there may be a reason it shouldn't be done this that way I'm not yet aware of, but this is the solution I came up with to trim down the amount of error logging code in my main code block.
Dim oConn, connStr
Set oConn = Server.CreateObject("ADODB.Connection")
connStr = "Provider=SQLOLEDB;Server=XX;UID=XX;PWD=XX;Databse=XX"
ON ERROR RESUME NEXT
oConn.Open connStr
If err.Number <> 0 Then : showError() : End If
Sub ShowError()
'You could write the error details to the console...
errDetail = "<script>" & _
"console.log('Description: " & err.Description & "');" & _
"console.log('Error number: " & err.Number & "');" & _
"console.log('Error source: " & err.Source & "');" & _
"</script>"
Response.Write(errDetail)
'...you could display the error info directly in the page...
Response.Write("Error Description: " & err.Description)
Response.Write("Error Source: " & err.Source)
Response.Write("Error Number: " & err.Number)
'...or you could execute additional code when an error is thrown...
'Insert error handling code here
err.clear
End Sub