enable-eoio-processing-96d61b2.md

Enable EOIO Processing

With the web services sequence protocol, you can enable exactly once in order (EOIO) processing for asynchronous web services.

Context

It can sometimes be important that service requests arrive at the provider side in the correct order. This is the case when database entries that depend on a previous write process are being written. If a database entry is changed that has not yet even been created, errors occur.

To ensure that calls are processed in the correct order, calls that belong together are given a sequence and then are evaluated by the provider.

If proxy object methods are called as part of a sequence, these calls are processed 'exactly once in order' (EOIO). If the proxy object methods are called without sequence, the methods are called 'exactly once' without a particular order.

To enable EOIO processing, proceed as follows.

Procedure

1. Create a consumer proxy by instantiating the generated class with a SOAP destination object. See Enable SOAP Communication in Your ABAP Code for more information.

2. Pass the proxy object to the factory method CL_WS_PROTOCOL_FACTORY=>GET_WS_SEQUENCE_PROTOCOL( ). The factory method returns a (proxy-specific) WS protocol object.

3. To enable EOIO processing, use methods WS_SEQUENCE_FACADE->BEGIN_EOIO_SEQUENCE( ) and WS_SEQUENCE_FACADE->END_EOIO_SEQUENCE( ). The proxy calls in between these two methods are processed EOIO.

4. Use COMMIT WORK to trigger web service calls in the EOIO sequence block.

   Sample Code:

   DATA(ws_sequence_facade) = cl_ws_protocol_factory=>get_sequence_protocol( proxy ).
   ws_sequence_facade->begin_eoio_sequence( ).
       <WS calls to be executed EOIO>
   ws_sequence_facade->end_eoio_sequence( ).

   Note:

   If there are multiple BEGIN/END_EOIO_SEQUENCE blocks, the corresponding sequences are executed independently of each other. All messages within a sequence are still executed exactly once in order.

Note:

First, you must get a SOAP destination object according to your SAP product as described in Enable SOAP Communication in Your ABAP Code.

Sample Code:

"get destination object
  TRY.
    DATA(proxy) = NEW zco_appointment_activity_reque(
                        destination = destination
                      ).
 
    DATA(ws_sequence_facade) = cl_ws_protocol_factory=>get_sequence_protocol( proxy ).
 
    ws_sequence_facade->begin_eoio_sequence( ).
    DATA(request1) = VALUE zco_appointment_activity_reque( ).
        proxy->check_operation(
          EXPORTING
            input = request1
        ).
    DATA(request2) = VALUE zco_appointment_activity_reque( ).
        proxy->check_operation(
          EXPORTING
            input = request2
        ).
    ws_sequence_facade->end_eoio_sequence( ).
 
    COMMIT WORK.   
 
      CATCH cx_ws_protocol_error
        "handle response
      CATCH cx_ai_system_fault.
        "handle error
      CATCH cx_srt_check_oper_fault.
        "handle error
  ENDTRY.