Chapter 5: Document Posting Engine
In the previous chapter, we saw how our financial data is carefully organized and validated inside the itab1 internal table. The data is clean, the debits and credits balance, and all our initial checks have passed. Now, we've reached the final, most critical step: sending this data to SAP to create an official financial document.
This is where the Document Posting Engine takes over.
The Final Handshake with SAP
Imagine you're at a bank trying to make a large, important wire transfer. You wouldn't just slide a pile of cash and a sticky note under the window. Instead, the bank teller follows a strict, secure procedure. They first verify your identity and account details, check that the funds are available, and get your final confirmation. Only then do they execute the transfer, making it official and irreversible.
The Document Posting Engine is that trusted bank teller for your data. It handles the final, secure "handshake" with SAP's core financial system. Its job is to ensure that your data is posted safely, correctly, and according to SAP's own rules, preventing any last-minute surprises.
A Two-Step Safety Protocol: Check, then Post
Directly posting data into a live financial system can be risky. What if a fiscal period was just closed by an administrator? What if a system-level configuration prevents this type of posting? These are errors that our Frontend Data Validation can't catch.
To prevent this, the engine uses a smart, two-step protocol that mirrors a "dress rehearsal" before the "live show."
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The Dress Rehearsal (Dry Run): The engine first sends the document to SAP in a special "simulation" mode. SAP runs through all its final checks as if it were posting the document but does not create anything. This catches any deep system-level errors and gives us a green light that the real post will succeed.
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The Live Show (Final Post): Once the dry run passes without any errors, the engine sends the exact same data again, but this time for real. Because we've already done a full simulation, we can be highly confident that this final step will work perfectly.
This two-step process is the key to the MassUpload tool's reliability.
How It Works: The BAPI Connection
The engine communicates with SAP using standard, SAP-approved interfaces called BAPIs (Business Application Programming Interfaces). Think of BAPIs as official "phone numbers" that SAP provides for external programs to call. They are safe, stable, and guarantee that data follows the rules.
The engine uses two specific BAPIs for its two-step process:
BAPI_ACC_DOCUMENT_CHECK: The "dress rehearsal" BAPI.BAPI_ACC_DOCUMENT_POST: The "live show" BAPI.
Here’s how the flow looks when you click the buttons on the workbench:
Under the Hood: From itab1 to a BAPI Call
When you click the Check Document or Upload button, a routine is triggered. Let's look at the bapi_check_docs routine as an example.
1. Preparing the Data
The BAPI needs the data in a very specific format. The first step is to take the data from our friendly Financial Document Line Item (itab1) and map it into the structures the BAPI expects.
The program loops through the relevant lines in itab1 and populates BAPI structures like docheader, accountgl, and currencyamount.
* Inside FORM bapi_check_docs
* 1. Prepare the document header (one per document)
docheader-comp_code = itab1-company_code.
docheader-doc_date = doc_date.
docheader-pstng_date = post_date.
docheader-ref_doc_no = itab1-reference.
" ... other header fields ...
* 2. Prepare the G/L account line items (one per line)
accountgl-itemno_acc = itm_count. " Line item number (1, 2, 3...)
accountgl-gl_account = itab1-account.
accountgl-item_text = itab1-text.
APPEND accountgl.
* 3. Prepare the currency/amount line items (one per line)
currencyamount-itemno_acc = itm_count.
currencyamount-currency = itab1-currency.
currencyamount-amt_doccur = itab1-amount.
APPEND currencyamount.
This code acts as a translator, converting our internal format into the official language the BAPI understands.
2. The Dry Run: Calling BAPI_ACC_DOCUMENT_CHECK
With the data prepared, the engine makes the first call. This is the "dress rehearsal."
* Still inside FORM bapi_check_docs
CALL FUNCTION 'BAPI_ACC_DOCUMENT_CHECK'
EXPORTING
documentheader = docheader
TABLES
accountgl = accountgl
currencyamount = currencyamount
return = return.
All the prepared data is passed to the BAPI. The BAPI's response—a list of success or error messages—is collected in the return table.
3. The Live Post: Calling BAPI_ACC_DOCUMENT_POST
If the dry run was successful, the user can click Upload. This triggers the create_document routine, which does the exact same data preparation but calls the "live show" BAPI instead.
* Inside FORM create_document
CALL FUNCTION 'BAPI_ACC_DOCUMENT_POST'
EXPORTING
documentheader = docheader
TABLES
accountgl = accountgl
currencyamount = currencyamount
return = return.
Notice how similar the calls are. This consistency is what makes the process so reliable.
4. Making It Permanent: BAPI_TRANSACTION_COMMIT
If the BAPI_ACC_DOCUMENT_POST call returns a success message, there's one final command: COMMIT.
IF return-type = 'S'. " If the BAPI returned a Success message
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'.
" Update the screen with the new document number
itab_doc-message_err = 'Posted Successfully'.
itab_doc-doc_number = return-message_v2. " The BAPI gives us the number!
MODIFY itab_doc.
ENDIF.
The COMMIT call is like pressing the "Save" button in SAP. It finalizes the transaction and makes the newly created financial document a permanent part of the system's records. The program then proudly displays the new document number on the screen.
Conclusion
The Document Posting Engine is the final and most powerful component in our workflow. It acts as a safe, reliable bridge to SAP's core financial system. By using a two-step "check then post" protocol with standard SAP BAPIs, it protects the integrity of the financial system while providing clear, actionable feedback to you. This transforms a high-risk operation into a confident, controlled, and successful final step.
Now that we've seen the whole process from start to finish, you might be wondering how the initial validations can check thousands of lines so quickly. The secret lies in a clever optimization technique.