BAPIs or SAP standard functions for USR are pretty handy in managing SAP user data in most cases but how about if an external system needs a USER GUID instead of BNAME to search SAP user ? What if a case of that you need to manage SAP user data only by GUID (Identity)?
Class CL_IDENTITY_FACTORY is providing very useful functions for user & for user Identity such as searching, deleting, creating, checking, and more. Even the use of CL_IDENTITY_FACTORY is not complicated as it has only static & public methods which giving you direct access without instantiating an object .
If you want to check SAP user existence in SAP system, Checking USR table might be the simplest way. However, here is an other way to do that
DATA : LV_BNAME TYPE XUBNAME,
LS_MESSAGE TYPE SYMSG,
LS_BNAME_EXIST TYPE SUID_ST_IDENTITY.
* Check User existance
LV_BNAME = CV_USERNAME.
IV_BNAME = LV_BNAME
ES_IDENTITY = LS_BNAME_EXIST ).
* IF LS_BNAME_EXIST IS INITIAL.
* RAISE EXCEPTION
IS_BNAME_EXIST = LS_BNAME_EXIST.
You can also send a query for user data or deal with multiple users or get info of BPs assigned to the users. To get further & deeper handling, check out class CL_IDENTITY .