A list is a medium used for the structured and formatted output of data. The following lists are available in ABAP:
- Classical lists, which are written to a list buffer using ABAP statements and displayed on a special list dynpro.
- Output of the SAP List Viewer (ALV), which is displayed in GUI controls during the processing of classical dynpros. ALV lists are accessed using classes, such as CL_SALV_TABLE (non-hierarchically tabular lists), CL_SALV_HIERSEQ_TABLE (hierarchically sequential lists), or CL_SALV_TREE (hierarchically tabular lists).
Classical lists are the only option to send ABAP data from ABAP programs directly to the SAP spool system as print lists. If SAP List Viewer is used, the lists that are displayed in the viewer are automatically converted to classical print lists during printing.
Use SAP List Viewer
Do not use classical lists. If dynpro-based, classical UI technologies are still used, SAP List Viewer (ALV) or other GUI control-based technologies should be used instead of classical lists in production programs.
Using classical lists is no longer recommended for the following reasons:
- The processing of lists is based on global data and events of the ABAP runtime environment.
- The list buffer that is used for classical lists is bound to an executable program or a dynpro sequence and not to classes and objects.
- It is almost impossible to separate presentation logic and application logic when writing to lists.
- The UI of a classical list is not standardized and thus usually not accessible.
The concept of classical lists is therefore mostly incompatible with the ABAP Objects concept, and classical lists cannot be encapsulated in function groups as easily as classical dynpros and selection screens.
While the application developer must ensure accessibility in classical lists with a great deal of effort, the ALV lists automatically comply with the accessibility requirements because the ALV already provides the required services, such as user-specific settings.
Small helper programs that are not intended for live use in application systems can continue to use
classical lists for system-related console output. The
WRITE list statement
here assumes the same role as System.out.println(...) in Java or printf in C.
In cases in which an ALV output seems to be overdimensioned, other methods are possible, such as Textedit Control or Browser Control (or its wrapping in dynamic documents) for the formatted output of non-tabular content. As before, accessibility must be guaranteed here.
For simple console output, XML-based output streams can also be used. An example of this is shown by the class CL_DEMO_OUTPUT_STREAM. The class CL_DEMO_OUTPUT demonstrates possible applications of this class. It is used in programs in the ABA Example Library.
Executing the program DEMO_CLASSICAL_REPORTING produces a classical list output. However, according to the above rule, using classical lists in application programs is no longer recommended.
Executing the program DEMO_ALV_REPORTING produces ALV lists with the same content and the same functions as the classical lists in the previous example. ALV lists replace classical lists in those cases in which classical dynpros are still used.