ABAP Help Document(14):7.Program程序流控制

7. Program Flow

7.1Logical Expresssions

参考1.2表达式中逻辑表达式。

7.2 Control Structures

分支语法：if,case;

示例：

"Branch
"分支语法
"if语法：
*IF log_exp1. 
*  [statement_block1] 
*[ELSEIF log_exp2. 
*  [statement_block2]] 
*... 
*[ELSE. 
*  [statement_blockn]] 
*ENDIF.
"case语法：
*CASE operand. 
*  [WHEN operand1 [OR operand2 [OR operand3 [...]]]. 
*    [statement_block1]] 
*  ... 
*  [WHEN OTHERS. 
*    [statement_blockn]] 
*ENDCASE. 
FORM f_branch.
  "if语句
  IF 1 > 0.
    ...
  ELSEIF 1 < 0.
    ...
  ELSE.
    ...
  ENDIF.
  "case语句
  DATA:lv_char TYPE C LENGTH 1.
  CASE lv_char.
    WHEN '1' OR '3'.
    WHEN '2'.
    WHEN OTHERS.
  ENDCASE.
ENDFORM.

循环语法：do,while,loop,provide,select

示例：

"循环语法
"do语法：
*DO [n TIMES]. 
*  [statement_block] 
*ENDDO. 
"while语法：
*WHILE log_exp 
*  [statement_block] 
*ENDWHILE.

程序中断

示例：

"程序中断
"语法
*WAIT UP TO sec SECONDS.

7.3 Exception Handling

异常分为可处理异常，不可处理异常。

可处理异常被ABAP运行时环境抛出，通过Program Raise Exception抛出，通过Try catch entry捕捉异常。

所有异常类父类，CX_ROOT。

异常种类：

CX_STATIC_CHECK

CX_DYNAMIC_CHECK

CX_NO_CHECK

SE24,Class Builder创建异常全局类或Program里创建本地异常类。以CX_, YCX_, ZCX_开头。

示例：

"Exception
"抛出异常
*RAISE [RESUMABLE] EXCEPTION
*  { {TYPE cx_class [EXPORTING p1 = a1 p2 = a2 ...]}
*  | oref }.
"try 捕获异常
*TRY.
*    [try_block]
*  [CATCH [BEFORE UNWIND] cx_class1 cx_class2 ... [INTO oref].
*    [catch_block]]
*    ...
*  [CLEANUP [INTO oref].
*    [cleanup_block]]
*ENDTRY.
CLASS zcx_exeception DEFINITION INHERITING FROM CX_STATIC_CHECK.
  PUBLIC SECTION.
    DATA: message TYPE string.
    METHODS:constructor IMPORTING iv_msg TYPE string.
ENDCLASS.
CLASS zcx_exeception IMPLEMENTATION.
  METHOD constructor.
    super->constructor( ).
    me->message = iv_msg.
  ENDMETHOD.
ENDCLASS.

CLASS zcl_test_exception DEFINITION.
  PUBLIC SECTION.
    METHODS:meth1 RAISING zcx_exeception.
    METHODS:meth2 RAISING RESUMABLE(zcx_exeception).
ENDCLASS.
CLASS zcl_test_exception IMPLEMENTATION.
  METHOD meth1.
    DATA:lo_exec TYPE REF TO zcx_exeception.
    TRY.
      RAISE EXCEPTION TYPE zcx_exeception EXPORTING iv_msg = 'no resumable exception'.
    CATCH BEFORE UNWIND zcx_exeception INTO lo_exec.
      WRITE:/ lo_exec->message.
    ENDTRY.
  ENDMETHOD.
  METHOD meth2.
    DATA:lo_exec TYPE REF TO zcx_exeception.
    TRY.
      RAISE RESUMABLE EXCEPTION TYPE zcx_exeception EXPORTING iv_msg = 'resumable exception'.
    CATCH zcx_exeception INTO lo_exec.
      WRITE:/ lo_exec->message.
    ENDTRY.
  ENDMETHOD.
ENDCLASS.

"抛出exception
FORM f_raise_exception.
  DATA:lo_exc TYPE REF TO zcx_exeception.
  TRY.
    "抛出异常
    RAISE EXCEPTION TYPE zcx_exeception EXPORTING iv_msg = 'test'.
  CATCH zcx_exeception INTO lo_exc.
    WRITE:/ lo_exc->message.
  ENDTRY.

  DATA:lo_test_exception TYPE REF TO zcl_test_exception.
  CREATE OBJECT lo_test_exception.
  TRY .
    lo_test_exception->meth1( ).
    lo_test_exception->meth2( ).
  CATCH zcx_exeception INTO lo_exc.
    WRITE:/ lo_exc->message.
  ENDTRY.
ENDFORM.

ABAP Exception异常树：