Sales order confirmation in batch - adding extended logic

The out of the box Sales order confirmation functionality allows us to either confirm Sales order using a click of a button (on Sales order form/list page) or we can schedule the confirmation of Sales order using a batch job (it also supports late selection query). This all works fine. However, if you want to perform additional tasks on each Sales order once it is confirmed, you will need to write some code. The class structure is something like that

FormLetterService
SalesFormLetter
SalesFormLetter_Confirmation

Any developer familiar to inheritance would go and override the run method of SalesFormLetter_Confirmation class to perform the additional updates after the super call and it will work perfect when a Sales order is confirmed using a button. However, it will NOT work as expected when runs under a batch. It is because, batch creates multi threaded tasks and leaves them to execute later. The code written in run method of SalesFormLetter_Confirmation class would run before the Sales order is actually confirmed (under different thread) and you will not achieve your desired results as code would not be execute for SOs being confirmed under a batch.

To overcome this issue, the code must be executed when the thread actually confirms the Sales order. After performing some debugging using Visual Studio and analysing the threads I found few ways to achieve the desired results and execute the custom code for each and every Sales order under the batch right after it gets Confirmed.

1. There is a class called "FormLetterServiceBatchTaskManager". It has run method - write your code there after the base class' run gets executed. Better check the this.ParmDocumentStatus to execute your code only for the document type you are working on. (if this.ParmDocumentStatus() == DocumentStatus::Confirmation)
2. Write your code in FormLetterService.run() method after journal gets created (Again, check the document status and execute your code only for your desired document type). 

There are some other classes which actually creates journal and they could also be considered for performing similar tasks based on your requirements.

1. FormLetterJournalCreate (Parent class - following are few of its child classes)
2. SalesConfirmJournalCreate
3. SalesPickingListJournalCreate etc.