How to Read Error Message in a Class-Based Workflow

In a class-based Workflow when an error occurs with the RAISING statement, the error message data can be sent to the Workflow.

Examples

MESSAGE ID sy–msgid TYPE sy–msgty NUMBER sy–msgno WITH sy–msgv1 sy–msgv2 sy–msgv3 sy–msgv4 RAISING error_occurred.

RAISE EXCEPTION TYPE ZCX_BO_ERROR_WITH_MESSAGE EXPORTING textid = ls_message.

In the Workflow, this error message is not directly available – however, usually, it is a good idea to show the error message to the user.

From the workflow task, we will need the workitem ID.
We need to define in the container a workitem ID to hold this data:
WorkitemID with type SWW_WIID
We need to bind the workitem ID in the Workflow task:
From &_WORKITEM.WORKITEMID&
To &WORKITEMID&
Then we have to write a method in the Workflow class to call FM SWL_WI_HEADER_READ:
CALL FUNCTION ‘SWL_WI_HEADER_READ’
   EXPORTING
     wi_id                         = WorkitemID
    ACT_LANGU                     = SY-LANGU
    I_ONLY_HEAD_STATUS_TYPE       = ‘ ‘
   changing
     workitem                      = ls_workitem
EXCEPTIONS
    WORKITEM_NOT_FOUND            = 1
    OTHERS                        = 2