场景：

第三方调用SAP接口，创建单据，如果对方因为某种原因在极短的时间内，使用重复数据连续调用了sap接口，怎样防止重复创建单据。

之前群里聊过这个问题，我把问题抛出来，大家随便聊聊而已。

场景其实挺简单，也很常见，至于怎么实现，无非是什么加锁，加日志之类的。

我也是做了一个简单测试。

场景是推送数据到sap，创建PO。

先创建了个log表：

然后建了个锁

然后写了俩函数，分别是用锁和用log表。

第一个函数

FUNCTION ZLM_CREATE_PO.*"----------------------------------------------------------------------*"*"本地接口：*"  IMPORTING*"     VALUE(IS_DATA) TYPE  ZLMT_PO_LOG OPTIONAL*"  EXPORTING*"     VALUE(ES_DATA) TYPE  ZLMT_PO_LOG*"----------------------------------------------------------------------
  DATA:LT_LOG TYPE TABLE OF ZLMT_PO_LOG.  DATA:LS_LOG TYPE ZLMT_PO_LOG.
  DATA:    LT_RETURN  LIKE TABLE OF BAPIRET2,    LT_POITEM  LIKE TABLE OF BAPIMEPOITEM,    LT_POITEMX LIKE TABLE OF BAPIMEPOITEMX,    LT_POCOND  LIKE TABLE OF BAPIMEPOCOND,    LT_POCONDX LIKE TABLE OF BAPIMEPOCONDX,    LS_POCOND  LIKE    BAPIMEPOCOND,    LS_POCONDX LIKE   BAPIMEPOCONDX.  DATA:    LS_POHEADER  LIKE BAPIMEPOHEADER,    LS_POHEADERX LIKE BAPIMEPOHEADERX,    LS_RETURN    LIKE BAPIRET2,    LS_POITEM    LIKE BAPIMEPOITEM,    LS_POITEMX   LIKE BAPIMEPOITEMX.  DATA:LV_PO_NUMBER LIKE  BAPIMEPOHEADER-PO_NUMBER.
*--------------------------------------------------------------------** 参数赋值*--------------------------------------------------------------------*
  IF IS_DATA IS NOT INITIAL.    MOVE-CORRESPONDING IS_DATA TO LS_LOG.  ELSE.
    CALL FUNCTION '/SAPSLL/GUID_CREATE'      IMPORTING        EV_GUID_32 = LS_LOG-GUID.
    LS_LOG-WEB_ORDER         = 'LM00001'  ."外部单据号    LS_LOG-BUKRS         = '1710'  ."公司代码    LS_LOG-BSART         = 'NB'  ."订单类型（采购）    LS_LOG-LIFNR         = 'USSU-VSF04'  ."供应商或债权人的帐号    LS_LOG-EKORG         = '1710'  ."采购组织    LS_LOG-EKGRP         = '002'  ."采购组    LS_LOG-MATNR         = 'MZ-RM-R300-01'  ."物料编号    LS_LOG-WERKS         = '1710'  ."工厂    LS_LOG-LGORT         = '171C'  ."库存地点    LS_LOG-KSCHA         = 'PMP0'  ."条件类型    LS_LOG-AMOUNT        = '1'  ."条件金额    LS_LOG-WAERS         = 'USD'  ."货币码
    LS_LOG-UNAME = SY-UNAME.    LS_LOG-DATUM = SY-DATUM.    LS_LOG-UZEIT = SY-UZEIT.
  ENDIF.
*--------------------------------------------------------------------** 枷锁*--------------------------------------------------------------------*
  CALL FUNCTION 'ENQUEUE_EZLMT_PO_LOG'    EXPORTING      MODE_ZLMT_PO_LOG = 'X'      MANDT            = SY-MANDT      WEB_ORDER        = LS_LOG-WEB_ORDER      _SCOPE           = '3'    EXCEPTIONS      FOREIGN_LOCK     = 1      SYSTEM_FAILURE   = 2      OTHERS           = 3.  IF SY-SUBRC <> 0.    LS_LOG-TYPE = 'E'.    LS_LOG-MESSAGE = '被锁'.
    INSERT ZLMT_PO_LOG FROM LS_LOG.    COMMIT WORK AND WAIT.
    ES_DATA = LS_LOG.    RETURN.  ENDIF.
*--------------------------------------------------------------------** 检查库表内该 web order是否已经成功创建 po*--------------------------------------------------------------------*  SELECT SINGLE * FROM ZLMT_PO_LOG INTO @DATA(LS_TMP)    WHERE  WEB_ORDER = @LS_LOG-WEB_ORDER.
  IF SY-SUBRC = 0.    LS_LOG-TYPE = 'E'.    LS_LOG-MESSAGE = '重复创建'.    INSERT ZLMT_PO_LOG FROM LS_LOG.    COMMIT WORK AND WAIT.
    ES_DATA = LS_LOG.    RETURN.  ENDIF.*--------------------------------------------------------------------** 赋值 call bapi*--------------------------------------------------------------------*  CLEAR LS_POHEADER.  CLEAR LS_POHEADERX.  LS_POHEADER-COMP_CODE      = LS_LOG-BUKRS.  LS_POHEADER-CURRENCY       = LS_LOG-WAERS.  LS_POHEADER-DOC_DATE       = SY-DATUM.  LS_POHEADER-DOC_TYPE       = LS_LOG-BSART.  LS_POHEADER-VENDOR         = LS_LOG-LIFNR.  LS_POHEADER-PURCH_ORG      = LS_LOG-EKORG.  LS_POHEADER-PUR_GROUP      = LS_LOG-EKGRP.  LS_POHEADERX-COMP_CODE     = 'X'.  LS_POHEADERX-DOC_TYPE      = 'X'.  LS_POHEADERX-VENDOR        = 'X'.  LS_POHEADERX-PURCH_ORG     = 'X'.  LS_POHEADERX-PUR_GROUP     = 'X'.  LS_POHEADERX-CURRENCY      = 'X'.  LS_POHEADERX-DOC_DATE      = 'X'.    CLEAR: LS_POITEM,LS_POITEMX.  CLEAR: LT_POITEM[],LT_POITEMX[].
  LS_POITEM-PO_ITEM         =  '10'.                   "采购凭证的项目编号  LS_POITEM-MATERIAL        = LS_LOG-MATNR.          "商品代码  LS_POITEM-QUANTITY        = 1."           "采购订单数量  LS_POITEM-PO_UNIT         = 'EA' .                   "采购订单的计量单位  LS_POITEM-PLANT           = LS_LOG-WERKS.          "工厂  LS_POITEM-STGE_LOC        = LS_LOG-LGORT.          "库存地点
  APPEND LS_POITEM TO LT_POITEM.

  LS_POITEMX-PO_ITEM         =  '10'.          "采购凭证的项目编号  LS_POITEMX-MATERIAL        = 'X'.            "商品代码  LS_POITEMX-QUANTITY        = 'X'.            "采购订单数量  LS_POITEMX-PO_UNIT         = 'X' .           "采购订单的计量单位  LS_POITEMX-PLANT           = 'X'.            "工厂  LS_POITEMX-STGE_LOC        = 'X'.            "库存地点

  APPEND LS_POITEMX TO LT_POITEMX.
  CLEAR LT_POCOND[].  CLEAR LT_POCONDX[].  CLEAR LS_POCOND.
  LS_POCOND-ITM_NUMBER = '10'.  LS_POCOND-COND_TYPE  = LS_LOG-KSCHA.  "定价条件  LS_POCOND-COND_VALUE = LS_LOG-AMOUNT.  LS_POCOND-CURRENCY   =  LS_LOG-WAERS.  "币别  LS_POCOND-CHANGE_ID   = 'I'.  "修改类型 I U  D
  APPEND LS_POCOND TO LT_POCOND.
  CLEAR LS_POCONDX.
  LS_POCONDX-ITM_NUMBER = '10'.  LS_POCONDX-COND_TYPE  = LS_LOG-AMOUNT.  "定价条件  LS_POCONDX-COND_VALUE = 'X'.  "价格  LS_POCONDX-CHANGE_ID = 'X'.  "修改类型

  IF LS_POCOND-CURRENCY IS NOT INITIAL.    LS_POCONDX-CURRENCY   = 'X'.  "币别  ENDIF.
  APPEND LS_POCONDX TO LT_POCONDX.
*& call bapi
  CALL FUNCTION 'BAPI_PO_CREATE1'    EXPORTING      POHEADER         = LS_POHEADER      POHEADERX        = LS_POHEADERX    IMPORTING      EXPPURCHASEORDER = LV_PO_NUMBER    TABLES      RETURN           = LT_RETURN      POITEM           = LT_POITEM      POITEMX          = LT_POITEMX      POCOND           = LT_POCOND      POCONDX          = LT_POCONDX.

*--------------------------------------------------------------------**  save log*--------------------------------------------------------------------*  LS_LOG-EBELN = LV_PO_NUMBER.  LS_LOG-TYPE = 'S'.  LS_LOG-MESSAGE = '创建成功'.
  LS_LOG-UNAME = SY-UNAME.  LS_LOG-DATUM = SY-DATUM.  LS_LOG-UZEIT = SY-UZEIT.
  ES_DATA = LS_LOG.
  INSERT ZLMT_PO_LOG FROM LS_LOG.
  CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'    EXPORTING      WAIT = 'X'.
*--------------------------------------------------------------------** 解锁*--------------------------------------------------------------------*  CALL FUNCTION 'DEQUEUE_EZLMT_PO_LOG'    EXPORTING      MANDT     = SY-MANDT      WEB_ORDER = LS_LOG-WEB_ORDER    .ENDFUNCTION.

仅仅是测试代码而已。

第二个函数，只是没用锁，自己把 加锁 解锁 注释掉就行了，

（LS_LOG-WEB_ORDER         = 'LM00002'）。

第一个函数没有重复数据。

第二个函数出现了问题：

大概就是这个意思了。

仅仅是简单测试了下，如果有什么不对的地方欢迎批评指正。谢谢！~

这个其实还有一个极端情况的问题，就是第一条锁释放后，到第一条数据落表的这个时间差里，进来的数据。

这个场景我没模拟出来。