Program | control | data | Database in programming, often need to use transactions. A business is a series of operations that must be successful, and all other steps must be undone as long as one operation fails. For example, using ASP to develop a network hard disk system, the user registration part of the things to do are:
To record user information into a database
Open a folder for users to store
Initialize User action Log
These three steps must use transactions, or in the event of a disk operation failure, but did not undo the database operation, it will cause only landing and can not operate the "dead user" phenomenon.
Because of the special development History of database system, small to access, large to DB2, all with transaction support. The above steps can therefore be expressed as follows:
On Error Resume Next
First step:
To record user information into a database in a transactional environment
If ERR Then
Close connection
Exit
Else
Step Two: Create a folder
If ERR Then
Roll back the first step database operation, exit
Else
Step three: Manipulate the log database in a transactional environment
If ERR Then
Roll back the first step and delete the folder created in the second step
Exit
End If
End If
End If
Commit transactions for the first step of the database operation
Commit transactions to the second step of the database operation
End
Each step needs to be judged, if it fails, you need to manually rollback the previous multi-step operation, so that the program becomes complex and difficult to understand. If you update your program in the future and add additional steps, you will need to nest more layers of If ... Else ... End If, making the program process more complex.
The correct solution is to use the ASP's transaction control capabilities. By contacting the MTS Service, IIS can control multiple systems that support transactions, and when the program issues a "failed" signal, all supporting transactions are automatically rolled back, even if the operation is formally completed, and a convenient manual rollback is provided for operations that do not support transactions. The example above is rewritten using the ASP transaction control function as follows:
<%@ TRANSACTION = Required%>
On Error Resume Next
Set conn=server.createobject ("ADODB. Connection ")
Conn.Open .....
Conn.execute "INSERT ...."
Conn.close
Set conn=nothing
Set conn2=server.createobject ("ADODB. Connection ")
Conn2.open .....
Conn2.execute "INSERT ...."
Conn2.close
Set conn2=nothing
Set fso=server.createobject ("Scripting.FileSystemObject")
Fso. CreateFolder "..."
If ERR Then
ObjectContext.SetAbort ' notifies all supporting transaction components to roll back and runs manual rollback code
Else
ObjectContext.SetComplete
End If
Set fso=nothing
Sub OnTransactionAbort
Response.Write "Error"
Fso. DeleteFile Server.MapPath ("a.txt") ' FSO manual rollback--delete folder
End Sub
Sub OnTransactionCommit
Response.Write "Complete the mission successfully."
End Sub
%>
The first line of <%@ TRANSACTION = Required%> indicates that this page of ASP files requires MTS transaction support. Each of the operations in the middle is written in a normal order, regardless of the rollback issue. At the end of the program to determine whether there are errors. If there is, call the ObjectContext SetAbort method, IIS notifies all supporting transaction components to rollback (primarily the database) through the MTS service, and runs sub OnTransactionAbort to manually rollback the operations that do not support transactions If no error occurs, the ObjectContext SetComplete method is invoked, and sub OnTransactionCommit is run to display the successful message.
The entire ASP program does not need to judge errors and rollback operations to write redundant code, only to be judged at the end, even if the future increase in multi-step operations, but only in the Sub OnTransactionAbort control can be very convenient, programmers can focus on process writing rather than writing error-correcting code.
In fact, ASP also provides a number of more useful features, waiting for us to use, do not think that ASP use scripting language, the function is necessarily weak.
