Templates in ABAP

Question

Hi,
I want a brief introduction to templates in ABAP.
I need to write a template which shall generate dynamic code. I am very new to this template concept in ABAP. Could some one please provide me good documents on how to write a template in ABAP or/and provide a simple sample program?
Regards,
Ravi

Answer 1

following is a template for example:
@--Template for generating CDS_READ_SERVICE--
*@ DATA: LT_SEGM         TYPE SMMW_CDS_SEGM_TTYP.
*@ DATA: LT_MAPP         TYPE SMMW_CDS_MAPP_TTYP.
*@ DATA: WA_SEGM         TYPE SMMW_CDS_SEGM.
*@ DATA: WA_MAPP         TYPE SMMW_CDS_MAPP.
*@ DATA: LS_HDR          TYPE MSB_HEADER.
*@ DATA: LS_MBOINFO      TYPE SMMW_CDS_MBO_INFO.
*@ DATA: META_OBJ        TYPE SMMW_GUID.
*@ DATA: msg_strname(40) TYPE C.
*@ DATA: memodblbin(40)  TYPE C,
*@       memodbltxt(40)  TYPE C.
*@ META_OBJ = I_META_OBJECT(32).
@ get MBO structure,version and sw component name
*@  CALL FUNCTION 'MSB_GET_MBO_HEADER_INFO'
*@    EXPORTING
*@      IM_MBO_VERSION_ID        = META_OBJ
*@    IMPORTING
*@      EX_MBO_HEADER            = LS_HDR
*@    EXCEPTIONS
*@      MISSING_IMPORT_PARAMETER = 1
*@      NO_SUCH_MBO              = 2
*@      MORE_THAN_ONE_MBO        = 3
*@      OTHERS                   = 4
*@  IF SY-SUBRC <> 0.
*@    MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*@         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
*@  ENDIF.
@ get MBO information by calling API SMMW_CDS_GET_MBODATA
*@  CALL FUNCTION 'MMW_CDS_GET_MBODATA'
*@    EXPORTING
*@      I_MBO_TRANS                = META_OBJ
*@    IMPORTING
*@      SEGM_TAB                   = LT_SEGM
*@      MAPP_TAB                   = LT_MAPP
*@      MBO_INFO                   = LS_MBOINFO
*@    EXCEPTIONS
*@      MBO_ID_IS_INITIAL          = 1
*@      PARENT_SEGMENT_NOT_FOUND   = 2
*@      OTHERS                     = 3
*@  IF SY-SUBRC <> 0.
*@    MESSAGE ID SY-MSGID TYPE SY-MSGTY NUMBER SY-MSGNO
*@         WITH SY-MSGV1 SY-MSGV2 SY-MSGV3 SY-MSGV4.
*@  ENDIF.
*@  msg_strname = LS_MBOINFO-MESGSTR_NAME.
*@  memodblbin  = LS_MBOINFO-BMEMTABLE_NAME.
*@  memodbltxt  = LS_MBOINFO-TMEMTABLE_NAME.
                   CDS READ SERVICE
   This method has been generated
   Never change it manually, please!!
   Transaction:  \LS_HDR-NAME\
   Template   :  \I_TEMPLATE\
   GenKey     : CDS_READ_SERVICE
   Generated on \SY-DATUM\ \SY-UZEIT\
             by \SY-UNAME\
CONSTANTS: LC_INSERT VALUE 'I',
            LC_UPDATE VALUE 'U',
            LC_DELETE VALUE 'D'.
DATA: LT_OBJ_LIST          TYPE  EXTRACTKEY_TT.
DATA: WA_OBJ_LIST          TYPE  SMMW_EXTRACTKEY.
DATA: LV_COUNT             TYPE  INT4.
DATA: RECORDS_NOT_FOUND    TYPE  BOOL VALUE ' '.
CONSTANTS: lv_sendbits(32) TYPE x VALUE
'FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF'.
*@  IF LS_HDR IS NOT INITIAL.
  DATA: MBO_STR TYPE \msg_strname\.
*@   IF LT_SEGM IS NOT INITIAL.
*@    LOOP AT LT_SEGM INTO WA_SEGM.
declaring tables and workareas for segment : \WA_SEGM-SEGM_NAME\
  DATA: LT_T\WA_SEGM-TABLENAME\  TYPE TABLE OF \WA_SEGM-TABLENAME\.
  DATA: WA_T\WA_SEGM-TABLENAME\  TYPE          \WA_SEGM-TABLENAME\.
  DATA: WA_S\WA_SEGM-GEN_NUM\  TYPE          \WA_SEGM-SEGM_STR\.
*@    ENDLOOP.
copy the extract key table to a local internal table.
  LT_OBJ_LIST[] = OBJ_LIST[].
  IF LT_OBJ_LIST IS INITIAL.
*...handle log here........
    EXIT.
  ELSE.
sort the table to delete adjacent duplicate entries
    SORT LT_OBJ_LIST BY EXTRACTKEY.
delete the duplicate entries from the table before processing
    DELETE ADJACENT DUPLICATES
      FROM LT_OBJ_LIST
      COMPARING EXTRACTKEY.
    DESCRIBE TABLE LT_OBJ_LIST LINES LV_COUNT.
    IF task EQ LC_DELETE OR task EQ LC_UPDATE.
      IF LV_COUNT GT 1.
*.....bulk message is only for task 'I' not for task 'U' or 'D'.
*.....Hadle log here.....
        OBJ_MISS[] = LT_OBJ_LIST[].
        EXIT.
      ENDIF.
    ENDIF.
    IF TASK EQ LC_DELETE.
prepare MBO message for the Extract keys whose task is DELETE
*@    LOOP AT LT_SEGM INTO WA_SEGM WHERE HIERARCHY EQ 1.
@   if the segment is root segment only.
      LOOP AT LT_OBJ_LIST INTO WA_OBJ_LIST.
         WA_S\WA_SEGM-GEN_NUM\-TASK = TASK.
         WA_S\WA_SEGM-GEN_NUM\-\WA_SEGM-KEYFIELD\ =
           WA_OBJ_LIST-EXTRACTKEY.
         WA_S\WA_SEGM-GEN_NUM\-EXTRACTKEY =
           WA_OBJ_LIST-EXTRACTKEY.
         APPEND WA_S\WA_SEGM-GEN_NUM\ TO MBO_STR-\WA_SEGM-SEGM_NAME\.
      ENDLOOP.
*@    ENDLOOP.
task is not 'D'.
    ELSE.
*@    SORT LT_SEGM BY HIERARCHY.
*@    LOOP AT LT_SEGM INTO WA_SEGM.
select statement to fill segment: \WA_SEGM-SEGM_NAME\
*@     IF WA_SEGM-HIERARCHY NE 1.
     IF RECORDS_NOT_FOUND IS INITIAL.
*@     ELSE.
       DESCRIBE TABLE LT_OBJ_LIST LINES LV_COUNT.
*@     ENDIF.
       SELECT * INTO TABLE LT_T\WA_SEGM-TABLENAME\
       FROM \WA_SEGM-TABLENAME\
       FOR ALL ENTRIES IN LT_OBJ_LIST
@    For root segment compare extractkey with synckey
*@     IF WA_SEGM-HIERARCHY = 1.
       WHERE \WA_SEGM-KEYFIELD\ = LT_OBJ_LIST-EXTRACTKEY.
@    For other than root segments compare extractkey with
@    extractkey only.
*@     ELSE.
       WHERE EXTRACTKEY = LT_OBJ_LIST-EXTRACTKEY.
*@     ENDIF.
*@     IF WA_SEGM-HIERARCHY = 1.
       IF SY-SUBRC <> 0.
   all the extractkeys are invalid hence send all to OBJ_MISS.
         OBJ_MISS[] = LT_OBJ_LIST[].
         RECORDS_NOT_FOUND = 'X'.
       ELSEIF LV_COUNT NE SY-DBCNT.
   Not all the keys are invalid.atleast one key is invalid.
*@     LOOP AT LT_MAPP INTO WA_MAPP
*@       WHERE SEGM_NAME = WA_SEGM-SEGM_NAME AND IS_SYNCKEY EQ 'X'.
          LOOP AT LT_OBJ_LIST INTO WA_OBJ_LIST.
           READ TABLE LT_T\WA_SEGM-TABLENAME\
           WITH KEY \WA_MAPP-SFLD_NAME\ = WA_OBJ_LIST-EXTRACTKEY
           TRANSPORTING NO FIELDS.
*@     ENDLOOP.
           IF SY-SUBRC <> 0.
            APPEND WA_OBJ_LIST TO OBJ_MISS.
           ENDIF.
         ENDLOOP.
       ENDIF.
*@     ENDIF.
   process all the records to set the value for task field.
       IF LT_T\WA_SEGM-TABLENAME\ IS NOT INITIAL.
         IF task EQ LC_UPDATE.
           WA_S\WA_SEGM-GEN_NUM\-SENDBITS = lv_sendbits.
         ENDIF.
         WA_S\WA_SEGM-GEN_NUM\-TASK = TASK.
         LOOP AT LT_T\WA_SEGM-TABLENAME\ INTO WA_T\WA_SEGM-TABLENAME\.
          move-corresponding WA_T\WA_SEGM-TABLENAME\
             to WA_S\WA_SEGM-GEN_NUM\.
*@       LOOP AT LT_MAPP INTO WA_MAPP
*@         WHERE SEGM_NAME = WA_SEGM-SEGM_NAME AND IS_MEMO NE SPACE.
          IF wa_t\wa_segm-tablename\-\wa_mapp-sfld_name\ IS NOT INITIAL.
*@        IF WA_MAPP-IS_MEMO EQ 'T'.
    select the text memo content from the db table
            SELECT SINGLE CONTENT
            FROM \memodbltxt\
            INTO WA_S\WA_SEGM-GEN_NUM\-\WA_MAPP-SFLD_NAME\
            WHERE tablename = '\WA_SEGM-TABLENAME\' AND
               tablekey = WA_T\WA_SEGM-TABLENAME\-\WA_SEGM-KEYFIELD\ AND
               tablefield = '\WA_MAPP-SFLD_NAME\'.
*@        ELSEIF WA_MAPP-IS_MEMO EQ 'B'.
    select the binary memo content from the db table
            SELECT SINGLE CONTENT
            FROM \memodblbin\
            INTO WA_S\WA_SEGM-GEN_NUM\-\WA_MAPP-SFLD_NAME\
            WHERE tablename = '\WA_SEGM-TABLENAME\' AND
               tablekey = WA_T\WA_SEGM-TABLENAME\-\WA_SEGM-KEYFIELD\ AND
               tablefield = '\WA_MAPP-SFLD_NAME\'.
*@        ENDIF.
          ENDIF.
*@       ENDLOOP.
          APPEND WA_S\WA_SEGM-GEN_NUM\ TO MBO_STR-\WA_SEGM-SEGM_NAME\.
         ENDLOOP.
       ENDIF.   " table LT_T\WA_SEGM-TABLENAME\ not initial.
*@     IF WA_SEGM-HIERARCHY NE 1.
      ENDIF.
*@     ENDIF.
*@    ENDLOOP.
    ENDIF.
  ENDIF.   " Object list not initial.
*@    LOOP AT LT_SEGM INTO WA_SEGM WHERE HIERARCHY EQ 1.
  IF MBO_STR-\WA_SEGM-SEGM_NAME\ IS NOT INITIAL.
    MBO_MESSAGE = MBO_STR.
  Filling Header of the MBO message if it is not empty.
    DESCRIBE TABLE MBO_STR-\WA_SEGM-SEGM_NAME\ LINES LV_COUNT.
*@    ENDLOOP.
    CALL FUNCTION 'SYSTEM_UUID_C_CREATE'
         IMPORTING
           uuid = MBO_COMM_HEADER-MESSAGE_ID.
    MBO_COMM_HEADER-SWCV_NAME    = '\LS_HDR-SWCV_NAME\'.
    MBO_COMM_HEADER-VERSION      = '\LS_HDR-VERSION\'.
    MBO_COMM_HEADER-MBO_NAME     = '\LS_HDR-NAME\'.
   GET TIME STAMP FIELD MBO_COMM_HEADER-SEND_TSTMP.
  This vale SEND_TSTMP filling involves some problem...
    MBO_COMM_HEADER-SEND_USR     = SY-UNAME.
    IF LV_COUNT EQ 1.
      MBO_COMM_HEADER-MESSAGE_TYPE = 'I'.
      READ TABLE OBJ_LIST INDEX 1 INTO WA_OBJ_LIST.
      IF SY-SUBRC = 0.
       MBO_COMM_HEADER-EXTRACT_KEY = WA_OBJ_LIST-EXTRACTKEY.
      ENDIF.
    ELSE.
      MBO_COMM_HEADER-MESSAGE_TYPE = 'B'.
    ENDIF.
  ENDIF.
*@   ENDIF.
*@  ENDIF.
I dont understand the notation *@ here...
Why is it used??
Regards,
Ravi