Why Use ABAP Object by Horst Keller

Why use ABAP Objects Horst Keller, Stefan Bresch ABAP Language, SAP AG

Learning Objectives



Explain the benefits of object oriented programming in general



Explain the benefits of ABAP Objects compared to classical ABAP



Understand why Unicode enabled ABAP Objects is the best language for business applications up to now

 SAP AG2003, TechED_Basel / ABAP256, ABAP256, Horst Horst Keller, Stefan Bresch Bresch / 2

Agenda Background Principal Features of ABAP Objects 

Encapsulation



Instantiation



Reuse via Inheritance



Interfacing



Events

Benefits of ABAP Objects 

Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion

ABAP256, Horst Horst Keller, Stefan Bresch Bresch / 3  SAP AG2003, TechED_Basel / ABAP256,

Next Topic Background Principal Features of ABAP Objects 

Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Agenda Background Principal Features of ABAP Objects 

Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Backgr Backgroun ound d – History History









ABAP Objects was introduced with SAP Basis, Basis, Release 4.5. 4.5. 

Classes



Interfaces



Events

ABAP Objects was completed with SAP Basis Release 4.6. 4.6. 

Inheritance



Compound interfaces



Dynamic Invoke

Some enhancements were added with SAP Web Application Server , Releases 6.10, 6.20, ... 

Friends



Object Services



Shared Objects

Preceding Tec TechEd hEd Work Worksho shops ps (available from [email protected] [email protected]))


Background Background – ABAP and and ABAP Objects Objects at the WAS WAS

User Interface (SAP GUI, Web, ...)

ABAP Web Application Server

... SELECT * FROM ... ...

ABAP Objects Persistent Data (Database, Files, ...)  SAP AG2003, TechED_Basel / ABAP256, ABAP256, Horst Horst Keller, Stefan Bresch Bresch / 6

Background Background – Object Orientation Orientation in ABAP ABAP

Pure Object Oriented ABAP World ?

ABAP

Non-ABAP

Technically possible! ABAP256, Horst Horst Keller, Stefan Bresch Bresch / 7  SAP AG2003, TechED_Basel / ABAP256,

Background Background – Object Orientation Orientation in ABAP ABAP

Objects with Application Logic

ABAP


Background – Object Orientation in ABAP

Persistence and Transaction Services provided by ABAP Object Services, as of Release 6.10  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 9


GUI Control Framework, Office Integration, Business Server Pages, etc.

ABAP

 SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 10


For example JavaScript (as of Release 6.10)

ABAP

Non-ABAP



Application Coding is here!


System Classes from Libraries


Inside Objects?

METHOD... DATA ... TYPE ... ... LOOP AT itab REFERENCE INTO ... ... ENDMETHOD.

Purified ABAP



Reality ...

CALL SCREEN ... CALL FUNCTION DESTINATION ... SELECT ...

ABAP

Non-ABAP

ABAP + ABAP Objects  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 14


Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Encapsulation – ABAP/4 (1) Encapsulation of global data

Event Driven Modularization Processes

* Global Declarations... DATA ...

No local data PROCESS ON ... MODULE ... ...

MODULE ... ... ENDMODULE.

START-OF-SELECTION ...

No local data

Runtime Environment

Dynpro


ABAP Program

Encapsulation – ABAP/4 (2)

Procedural Programming Model * Global Declarations ... DATA ... MODULE ... ... CALL FUNCTION ... PERFORM ... ... ENDMODULE.

FORM ... DATA ... ... ENDFORM.

Local data

ABAP Program

Encapsulation can be circumvented!

* Global Declarations ... DATA ... FUNCTION ... DATA ... ... PERFORM ... ... ENDFUNCTION. FORM ... DATA ... ... SELECT * FROM ... ... ENDFORM.

Encapsulation of global data Local data

Local data

Function Group


Encapsulation – Example ABAP/4 (1)

FUNCTION-POOL account.

Encapsulation of an account

DATA current_amount TYPE accounts-amount.

FUNCTION deposit. current_amount = current_amount + amount. ENDFUNCTION.

FUNCTION withdraw. IF current_amount > amount. current_amount = current_amount - amount. ELSE. RAISE EXCEPTION TYPE cx_negative_amount. ENDIF. ENDFUNCTION.

Function Group  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 18

Function modules work with one account

No possibility to interact with other accounts

Encapsulation – Example ABAP/4 (2)

FUNCTION-POOL account. DATA account_tab TYPE SORTED TABLE OF accounts WITH UNIQUE KEY id . LOAD-OF-PROGRAM. SELECT * FROM accounts INTO TABLE account_tab.

FUNCTION deposit. DATA account_wa TYPE accounts. READ TABLE account_tab INTO account_wa WITH TABLE KEY id = id . account_wa-amount = account_wa-amount + amount. MODIFY TABLE account_tab FROM account_wa. ENDFUNCTION.

All data in one table

Function modules work on shared data


Encapsulation – Example ABAP/4 (3) FUNCTION withdraw. DATA account_wa TYPE accounts. READ TABLE account_tab INTO account_wa WITH TABLE KEY id = id . IF account_wa-amount > amount. account_wa-amount = account_wa-amount - amount. MODIFY TABLE account_tab FROM account_wa. ELSE. RAISE EXCEPTION TYPE cx_negative_amount. ENDIF. ENDFUNCTION. FUNCTION transfer. CALL FUNCTION 'WITHDRAW' EXPORTING id = id_from amount = amount. CALL FUNCTION 'DEPOSIT' EXPORTING id = id_to amount = amount. ENDFUNCTION.


Data identified by input parameters

Encapsulation – ABAP Objects

Classes CLASS ... DEFINITION. PUBLIC SECTION. METHODS ... PRIVATE SECTION. DATA ... Encapsulation ... of Attributes ENDMETHOD. ENDCLASS.

CLASS ... DEFINITION. PUBLIC SECTION. METHODS ... PRIVATE SECTION. DATA ... Encapsulation ... of Attributes ENDMETHOD. ENDCLASS.

CLASS ... IMPLEMENTATION. METHOD... Local data DATA ... ... CALL METHOD ... ... ENDMETHOD. ENDCLASS.

CLASS ... IMPLEMENTATION. METHOD... Local data DATA ... ... SELECT * FROM ... ... ENDMETHOD. ENDCLASS.

ABAP Program

Class Pool


Encapsulation – Example ABAP Objects (1) A class unites functionality with data

CLASS account DEFINITION. PUBLIC SECTION. METHODS: constructor IMPORTING id TYPE accounts-id, deposit IMPORTING amount TYPE accounts-amount, withdraw IMPORTING amount TYPE accounts-amount RAISING cx_negative_amount, transfer IMPORTING amount TYPE accounts-amount target TYPE REF TO account RAISING cx_negative_amount. PRIVATE SECTION. DATA amount TYPE accounts-amount. Only data ENDCLASS. relevant for one

object is needed

Class Pool  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 22

Encapsulation – Example ABAP Objects (2) CLASS account IMPLEMENTATION. METHOD constructor. SELECT SINGLE amount FROM accounts INTO (amount) WHERE id = id. ENDMETHOD. METHOD deposit. me->amount = me->amount + amount. ENDMETHOD. METHOD withdraw. IF me->amount > amount. me->amount = me->amount - amount. ELSE. RAISE EXCEPTION TYPE cx_negative_amount. ENDIF. ENDMETHOD. METHOD transfer. me->withdraw( amount ). target->deposit( amount ). ENDMETHOD. ENDCLASS.



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Each object is initialized individually

An object works on its own data, no business key needed

An object can address other objects

Instantiation – ABAP/4

External Procedure Calls

Instances of programs with global data

... ...

Only one instance of each program

Function group 2

Function group 1

CALL FUNCTION ...

ABAP program

No explicite instantiation, no control of lifetime

Internal session of an ABAP program External session


Instantiation – Example ABAP/4

DATA: id1(8) TYPE n, id2(8) TYPE n, amnt TYPE p DECIMALS 2, exc_ref TYPE REF TO cx_negative_amount, text TYPE string.

First call instantiates function group

TRY. id1 = ... id2 = ... amnt = ... CALL FUNCTION 'TRANSFER' EXPORTING id_from = id1 id_to = id2 amount = amnt. CATCH cx_negative_amount INTO exc_ref. text = exc_ref->get_text( ). MESSAGE text TYPE 'I'. ENDTRY.

ABAP Program  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 26

Business keys identify data No static type check

Instantiation – ABAP Objects

Creation of Objects

Many instances of one class

Instances of classes with attributes and an identity

Explicit instantiation, control of lifetime

CREATE OBJECT oref TYPE class.

ABAP program

oref2

oref1

Internal session of an ABAP program External session


Instantiation – Example ABAP Objects

DATA: account1 account2 amnt exc_ref text

TYPE TYPE TYPE TYPE TYPE

REF TO account, REF TO account, p DECIMALS 2, REF TO cx_negative_amount, string.

CREATE OBJECT: account1 EXPORTING id = ..., account2 EXPORTING id = ... TRY. amnt = ... account1->transfer( EXPORTING amount = amnt target = account2 ). CATCH cx_negative_amount INTO exc_ref. text = exc_ref->get_text( ). MESSAGE text TYPE 'I'. ENDTRY.


Object reference variables as explicit handles Independent objects based on the same class

Static type check

Natural working with instances


Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Reuse – ABAP/4



Reuse of generalized procedures



No support for specialization



Typical results: 

Large function groups



Extensive parameter interfaces



Subdividing tasks via CASE


Reuse – Example ABAP/4 (1)

FUNCTION withdraw. *"-------------------------------------------------------------*" IMPORTING *" REFERENCE(ID) TYPE ACCOUNTS-ID Steering *" REFERENCE(KIND) TYPE C DEFAULT 'C‚ parameters *" REFERENCE(AMOUNT) TYPE ACCOUNTS-AMOUNT *" RAISING *" CX_NEGATIVE_AMOUNT Additional *" CX_UNKNOWN_ACCOUNT_TYPE *"-------------------------------------------------------------- exception CASE kind. WHEN 'C'. „Checking account PERFORM withdraw_from_checking_account USING id amount. WHEN 'S'. "Savings account PERFORM withdraw_from_saving_account USING id amount. WHEN OTHERS. RAISE EXCEPTION TYPE cx_unknown_account_type. ENDCASE. ENDFUNCTION.

Procedure calls with parameter passing


Reuse – Example ABAP/4 (2) FORM withdraw_from_checking_account USING l_id TYPE accounts-id l_amount TYPE accounts-amount. DATA account_wa TYPE accounts. READ TABLE account_tab INTO account_wa WITH TABLE KEY id = l_id. account_wa-amount = account_wa-amount - l_amount. MODIFY TABLE account_tab FROM account_wa. IF account_wa-amount < 0. ... " handle debit balance ENDIF. ENDFORM. Specialized FORM withdraw_from_savings_account procedures, USING l_id TYPE accounts-id no code l_amount TYPE accounts-amount reuse RAISING cx_negative_amount. DATA account_wa TYPE accounts. READ TABLE account_tab INTO account_wa WITH TABLE KEY id = l_id. IF account_wa-amount > l_amount. account_wa-amount = account_wa-amount - l_amount. MODIFY TABLE account_tab FROM account_wa. ELSE. RAISE EXCEPTION TYPE cx_negative_amount. ENDIF. ENDFORM.


Reuse – ABAP Objects



Reuse of general classes



Specialization via inheritance



Benefits 

Small classes



Minimal parameter interfaces



Polymorphism (CASE-less programming)



enhanced Modeling capabilities


Reuse – Example ABAP Objects (1)

General superclass CLASS account DEFINITION. PUBLIC SECTION. ... PROTECTED SECTION. DATA amount TYPE accounts-amount. ENDCLASS.

CLASS account IMPLEMENTATION. ... METHOD withdraw. me->amount = me->amount - amount. ENDMETHOD. ... ENDCLASS.


Data sharing with subclasses

General method implementation


Special subclass CLASS checking_account DEFINITION INHERITING FROM account. PUBLIC SECTION. METHODS withdraw REDEFINITION. ENDCLASS.

CLASS checking_account IMPLEMENTATION. METHOD withdraw. super->withdraw( amount ). IF me->amount < 0. ... " handle debit balance ENDIF. ENDMETHOD. ENDCLASS.

Method redefinition

Call of general implementation

Special method implementation



Special subclass CLASS savings_account DEFINITION INHERITING FROM account. PUBLIC SECTION. METHODS withdraw REDEFINITION. ENDCLASS.

CLASS savings_account IMPLEMENTATION. METHOD withdraw. IF me->amount > amount. super->withdraw( amount ). ELSE. RAISE EXCEPTION TYPE cx_negative_amount. ENDIF. ENDMETHOD. ENDCLASS.


Method redefinition

Special method implementation Call of general implementation


DATA: account1 account2 amnt exc_ref text

TYPE TYPE TYPE TYPE TYPE

REF TO account, REF TO account, p DECIMALS 2, REF TO cx_negative_amount, string.

CREATE OBJECT: account1 TYPE checking_account EXPORTING id = ..., account2 TYPE savings_account EXPORTING id = ... TRY. amnt = ... account1->transfer( EXPORTING amount = amnt target = account2 ). CATCH cx_negative_amount INTO exc_ref. text = exc_ref->get_text( ). MESSAGE text TYPE 'I'. ENDTRY.

Polymorphism



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Same object reference variables as before General handles for specialized objects

Same usage of objects as before!

Interfaces – ABAP/4



Limited support for interfaces: 

Global data as interfaces between programs



Selection screens as interfaces for executable programs



Parameter interfaces for procedures



No standalone interfaces


Interfaces – ABAP Objects (1)



The interface of a class to the outside is defined by its public section



The interface of a class allows access to data and functionality



The interface of a class is inherited from its superclasses



Interfaces can be defined standalone



Standalone Interfaces INTERFACE if1. METHODS: m1 ... ... ENDINTERFACE.

CLASS cl_.... INTERFACES: if1, if2. ... ENDINTERFACE.

oref1

oref2

INTERFACE if2. METHODS: m2 ... ... ENDINTERFACE.

METHOD if1~ m1. ... METHOD if2~ m2. ...

DATA: oref1 TYPE REF TO if1, oref2 TYPE REF TO if2.  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 41




Benefits of standalone interfaces: 

Can be defined by client



Independency from implementation



Polymorphism



Separation of independent characteristics


Interfaces – Example (1)

CLASS account DEFINITION. PUBLIC SECTION. INTERFACES if_serializable_object. ... ENDCLASS.

Class Pool One interface in different classes CLASS customer DEFINITION. PUBLIC SECTION. INTERFACES if_serializable_object. ... ENDCLASS.

Class Pool


Interfaces – Example (2)

DATA: account TYPE REF TO account, customer TYPE REF TO customer, serializable_objects TYPE TABLE OF REF TO if_serializable_object, serializable_object TYPE REF TO if_serializable_object, xmlstr TYPE string. CREATE OBJECT: account EXPORTING id = ..., customer. APPEND: account TO serializable_objects, customer TO serializable_objects. ... LOOP AT serializable_objects INTO serializable_object. CALL TRANSFORMATION id SOURCE obj = serializable_object RESULT XML xmlstr. ENDLOOP.

Interface reference variables

Instantiation of classes Collection of references to objects of different classes Polymorphism



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Events – ABAP/4



Classical Runtime Events: 

PAI, PBO



Selection Screen Events



Reporting Events



List Events



No program defined events



No triggering of events in program


Events – ABAP Objects (1)

Events are components of classes

METHOD... ... RAISE EVENT evt ... ENDMETHOD.

METHODS handler FOR EVENT evt ... METHOD handler ... ENDMETHOD.

oref2 oref1 METHOD... ... SET HANDLER oref1->handler FOR oref2. ... ENDMETHOD.  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 47

Events – ABAP Objects (2)



Benefits of events in ABAP Objects: 

indirect method call



decoupling of caller and handler



two stages of publish and subscribe



explicit exporting parameters


Events – Example (1)

CLASS checking_account DEFINITION INHERITING FROM account. PUBLIC SECTION. Allows the class to METHODS deposit REDEFINITION. publish an event ... EVENTS consulting_required EXPORTING value(amount) TYPE accounts-amount. PRIVATE SECTION. DATA limit TYPE accounts-amount VALUE '5000.00'. ENDCLASS.

CLASS checking_account IMPLEMENTATION. ... METHOD deposit. super->deposit( amount ). IF me->amount > limit. RAISE EVENT consulting_required EXPORTING amount = me->amount. ENDIF. ENDMETHOD. ENDCLASS.

Announces a state change that requires an action


Events – Example (2)

CLASS consultant DEFINITION. PUBLIC SECTION. Static subscription, METHODS constructor. ... allows the class to PRIVATE SECTION. handle an event ... METHODS receive_notification FOR EVENT consulting_required OF checking_account. ENDCLASS.

CLASS consultant IMPLEMENTATION. Dynamic METHOD constructor. ... subscription IF ... SET HANDLER me->receive_notification FOR ALL INSTANCES. ENDIF ... ENDMETHOD. ... METHOD receive_notification. " do something Event handling ENDMETHOD. ENDCLASS.



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Simplicity – ABAP/4 (1)

ABAP/4 coding might be simple, but ... REPORT simple_report. NODES spfli. GET spfli. WRITE: / spfli-carrid, spfli-connid ...

ABAP Program

... who knows really what’s happening here?


Simplicity – ABAP/4 (2)

This is what happens after SUBMIT: Program is loaded, start values are set LOAD-OF-PROGRAM

Selection screen values are set INITIALIZATION

Call of selection screen

In parallel, subroutines of a logical database are implicitly called!

AT SELECTION-SCREEN ... START-OF-SELECTION GET spfli END-OF-SELECTION

Still simplified scheme! The exact program flow depends on different settings

Call of list processing for basic list AT LINE-SELECTION, ...


Simplicity – ABAP Objects

ABAP Objects is simple because: 



There are only a few orthogonal basic concepts 

Classes contain attributes and methods



Objects are instances of classes



Objects are adressed via references



Accessibility is clearly defined by the object’s interface

Programming with objects is more natural than handling data via procedures



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Explicitness

ABAP/4 has many implicit features, e.g.: 



Implicit interfaces via global data 

Dynpros



Logical Databases

Programs are controlled by runtime environment 

Programs are driven from Dynpros



Program execution via SUBMIT

ABAP Objects is explicit 

no hidden concepts



no “black magic”


Explicitness – Example (1)

Classes instead of logical data bases

Simple example for a class that works like a logical database with a single node

CLASS ldb DEFINITION. PUBLIC SECTION. METHODS read_spfli. EVENTS spfli_ready EXPORTING value(values) TYPE spfli. PRIVATE SECTION. DATA spfli_wa TYPE spfli. ENDCLASS. Explicit

Interface

CLASS ldb IMPLEMENTATION. METHOD read_spfli. SELECT * FROM spfli INTO spfli_wa. RAISE EVENT spfli_ready EXPORTING values = spfli_wa. ENDSELECT. ENDMETHOD. ENDCLASS.

Events with parameters


Explicitness – Example (2)

Class instead of report program Simple example for a class that works like a report

Start via an OO Transaction

CLASS report DEFINITION. PUBLIC SECTION. METHODS start. PRIVATE SECTION. DATA spfli_tab TYPE TABLE OF spfli. METHODS: get_spfli FOR EVENT spfli_ready OF ldb IMPORTING values, display_spfli. ENDCLASS.

ABAP Program


Explicit event handling

Decoupling of data display from data handling

Explicitness – Example (3) CLASS report IMPLEMENTATION. METHOD start. DATA ldb TYPE REF TO ldb. CREATE OBJECT ldb. SET HANDLER me->get_spfli FOR ldb. ldb->read_spfli( ). display_spfli( ). ENDMETHOD. METHOD get_spfli. APPEND values TO spfli_tab. ENDMETHOD.

Simplicity does not necessarily mean less coding

METHOD display_spfli. DATA alv_list TYPE REF TO cl_gui_alv_grid. CREATE OBJECT alv_list EXPORTING i_parent = cl_gui_container=>screen0. alv_list->set_table_for_first_display( EXPORTING i_structure_name = 'SPFLI‚ CHANGING it_outtab = spfli_tab ). CALL SCREEN 100. ENDMETHOD. ENDCLASS.



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Maintainability

Programs using ABAP Objects are 



easier to maintain 

program structure better readable



better navigation

more reliable 

encapsulation



secure typing



surprise free


Maintainability – Program Structure

No declaration of procedures FUNCTION f1. PERFORM s1 ... ENDFUNCTION. FORM s1 ... ... PERFORM f2 ... ... ENDFORM. FORM s2 ... ... PERFORM s3 ... ENDFORM.

Mixture of different procedures

FORM s3 ... ... ENDFORM.


CLASS ... DEFINITION. PUBLIC SECTION. METHODS: m1 ... PRIVATE SECTION. METHODS: m2 ... m3 ... ENDCLASS.

Declaration mandatory

CLASS ... IMPLEMENTATION. METHOD m1. ... Navigation m2( ... ). ... ENDMETHOD. METHOD m2. ... m3( ... ). ... ENDMETHOD. METHOD m3. ... ENDMETHOD. ENDCLASS.

Class Pool

Only methods


Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Purified ABAP - Syntax (1)

ABAP/4 has developed over a long period of time 

large number of obsolete statements



overlapping concepts



highly specialized concepts



surprising implicit behavior



difficult to learn


Purified ABAP - Syntax (2)

ABAP Objects reduces the complexity of ABAP 

many obsolete statements and additions are forbidden



many implicit syntax completions must be done explicit



wrong handling of data is restricted


Purified ABAP – Syntax Examples (1)

Clean-Up in ABAP Objects 

No implicit work areas 

No internal tables with header lines specification of work areas

explicit



No TABLES work areas no data sharing between programs, explicit specification of work areas in Open SQL , ... Obsolete declaration!

Two data objects with one name!

DATA BEGIN OF itab OCCURS 10. ... CLEAR itab.

DATA itab TYPE TABLE OF ... ... CLEAR itab.

TABLES dbtab. SELECT * FROM dbtab.

DATA wa TYPE dbtab. SELECT * FROM dbtab INTO wa.

ABAP/4

Inappropriate short forms


ABAP Objects



No implicit typing of field-symbols and formal parameters Unexpected behavior!

FIELD-SYMBOLS .

FIELD-SYMBOLS TYPE ANY.

IF IS ASSIGNED. ... ENDIF.

IF IS ASSIGNED. ... ENDIF.

ABAP/4

ABAP Objects Expected behavior!




No wrong data handling

DATA number TYPE i VALUE ... TRANSLATE number TO UPPER CASE.

ABAP/4

TRANSLATE number TO UPPER CASE.

ABAP Objects Undefined behavior!


DATA number TYPE i VALUE ...

Syntax error

Purified ABAP - Semantics

Unicode-enabled ABAP 

Static type checks specified more precisely



Byte and character strings processed separately



Structures handled appropriately for their type using structural equivalence rules



Uncontrolled memory manipulation no longer permitted


Purified Semantics – Example (1)


Structures are assigned fragment by fragment DATA: BEGIN OF struc1, col1(2) TYPE c VALUE 'AB', col2(2) TYPE c VALUE 'CD', END OF struc1.

Code page dependent representation of blanks

DATA: BEGIN OF struc2, col1(4) TYPE c, col2 TYPE i, END OF struc2. struc2 = struc1.

struc2 in non-Unicode-enabled ABAP:

ABCD

####

struc2 in Unicode-enabled ABAP:

ABCD

0

Type specific


Purified Semantics – Example (2)


No access to memory outside a data object DATA: text1(10) TYPE c, text2(10) TYPE c VALUE 'ABCDEFGHIJ', off TYPE i. FIELD-SYMBOLS TYPE c. DO 15 TIMES. off = sy-index - 1. ASSIGN text1+off(1) TO . IF IS ASSIGNED. = 'X'. ENDIF. ENDDO.

Memory overwriting, even for references!

text2 in non-Unicode-enabled ABAP:

XXXXXFGHIJ

text2 in Unicode-enabled ABAP:

ABCDEFGHIJ

Memory protection  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 71

Purified Syntax + Purified Semantics

Unicode-enabled ABAP Objects! 

Unicode-enabled ABAP Objects is the best ABAP available up to now!



If you use Unicode-enabled ABAP Objects, you program automatically according to the rules of purified syntax and semantics



Even if you do not exploit the real “object oriented” features, programs written in Unicode-enabled ABAP Objects are 

more robust



less error prone



better to maintain



Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Future Orientation 

(Unicode enabled) ABAP Objects is part of an ongoing evolution

Don‘t get lost!

Migration

R/2 ABAP

ABAP/4


ABAP Objects

Unicode enabled

Possible future developments


Encapsulation



Instantiation






Interfacing



Events


Simplicity



Explicitness



Maintainability



Purified ABAP



Future Orientation

Conclusion


Conclusion - Summary

ABAP Objects offers 

better encapsulation



better interfaces



better techniques for reuse



more static type security



support for multiple instantiation



better support for dynamic programming


Conclusion - Recommendation



Everybody programming in ABAP should use ABAP Objects for new and ongoing projects  take

advantage of object oriented features

 use

methods as far as possible, even if you stay within the procedural programming model

 do

not use subroutines any more

 use

function modules only when technically necessary (RFC, encapsulation of screens etc.)

 disentangle

classical ABAP from ABAP Objects


Appendix

Stricter syntax in ABAP Objects Stricter syntax in Unicode programs Example for encapsulation of screens


Appendix A – Stricter Syntax in ABAP Objects (1/2) Notation: No special characters in names, no length specifications <= zero, no multi-line literals  Declarations: LIKE references to data objects only; no implicit lengths or decimal places in TYPES; no length specifications for data types i, f, d , or t; no operational statements in structure definitions; FIELDS , RANGES, INFOTYPES , TABLES , NODES, COMMON PART , OCCURS , NONLOCAL not permitted  Forbidden operations: CLEAR … WITH NULL , PACK, MOVE ... PERCENTAGE , ADD-CORRESPONDING, DIVIDE-CORRESPONDING , SUBTRACTCORRESPONDING , MULTIPLY-CORRESPONDING , ADD THEN ... UNTIL ... , ADD FROM ... TO ... , CONVERT {DATE|INVERTED DATE} 

String processing: Not permitted on numeric data objects  Field symbols: No implicit types; FIELD-SYMBOLS … STRUCTURE , ASSIGN ... TYPE, ASSIGN LOCAL COPY OF , ASSIGN TABLE FIELD not permitted  Logic expressions: ><, =<, => not permitted, table used with IN must be a selection table  Control structures: No operational statements between CASE and WHEN, ON-ENDON not permitted 


Appendix A – Stricter Syntax in ABAP Objects (2/2) 

Internal tables: No headers, no implicit work areas, no redundant key specifications, compatible work areas where necessary, obsolete READ variants and COLLECT ... SORTED BY , WRITE TO itab , PROVIDE (short form) not permitted



Procedures (methods): No implicit type assignment, compatible initial values only, passing sy-subrc not permitted, raising undefined exceptions not permitted



Program calls: No joint use of USING and SKIP FIRST SCREEN when calling transactions, passing formal parameters implicitly in CALL DIALOG not permitted Database accesses: No implicit work areas, no *-work areas, READ, LOOP, REFRESH FROM on database tables not permitted, VERSION addition to DELETE and MODIFY not permitted, no PERFORMING addition in Native SQL Data cluster : No implicit identifiers, passing parameters explicitly not permitted, no implicit work areas, MAJOR-ID and MINOR-ID not permitted Lists: DETAIL, SUMMARY , INPUT , MAXIMUM , MINIMUM , SUMMING , MARK , NEW SECTION and obsolete print parameters not permitted








Appendix B – Stricter Syntax in Unicode Programs 

Offset/length accesses: Only performed on character-type or byte-type ranges, and only on flat character-type initial parts of structures



Memory accesses: No access to memory outside a data object



Separation of byte string and character string processing: Explicit specification with IN BYTE MODE or IN CHARACTER MODE ; appropriate types expected – for character strings this means only c, d , n, t, string, and flat structures with purely character-type components



Structures: When assigning and comparing you must take the Unicode fragment view into consideration



File interface: Implicitly opening files not permitted; access, storage, and coding type must be specified explicitly; no write access to read-only files



Conversions: TRANSLATE ... CODE PAGE ... , TRANSLATE ... NUMBER FORMAT ... not permitted



OPEN SQL: Stricter conditions for work areas



Type assignment using STRUCTURE: Stricter checks on assignments to field symbols and formal parameters typed using STRUCTURE



Function module calls: A specified formal parameter of a function module must be available


Appendix C – Encapsulation of Screens (1)

Encapsulation of screens in function groups FUNCTION-POOL flight_screens. SELECTION-SCREEN BEGIN OF SCREEN 100 AS WINDOW. PARAMETERS: p_carrid TYPE sflight-carrid, p_connid TYPE sflight-connid, p_fldate TYPE sflight-fldate. SELECTION-SCREEN END OF SCREEN 100. TABLES sflight. FUNCTION get_flight_parameters. CALL SELECTION-SCREEN 100 STARTING AT 10 10. ... " checks carrid = p_carrid. connid = p_connid. fldate = p_fldate. ENDFUNCTION. FUNCTION get_plane_type. sflight-planetype = plane_type. ... " preparation CALL SCREEN 200 STARTING AT 10 10. ... " checks plane_type = sflight-planetype. ENDFUNCTION.


Selection Screen Interface data for dynpro

Screen handling in function modules

Further step: Local classes in function group as screen handlers

Appendix C – Encapsulation of Screens (2)

Object driven usage of screens CLASS flights DEFINITION. PUBLIC SECTION. METHODS: constructor, change_plane_type. PRIVATE SECTION. DATA flight TYPE sflight. ENDCLASS.

Call of functions with parameters

Class Pool

CLASS flights IMPLEMENTATION. METHOD constructor. DATA: carrid TYPE sflight-carrid, connid TYPE sflight-connid, fldate TYPE sflight-fldate. CALL FUNCTION 'GET_FLIGHT_PARAMETERS' IMPORTING carrid = carrid connid = connid fldate = fldate. SELECT SINGLE * FROM sflight INTO flight WHERE carrid = carrid AND connid = connid AND fldate = fldate. ENDMETHOD. METHOD change_plane_type. CALL FUNCTION 'GET_PLANE_TYPE' CHANGING plane_type = flight-planetype. ENDMETHOD. ENDCLASS.


Always the first source of information

http://www.intelligenterp.com/feature/archive/heymann.shtml http://www.intelligenterp.com/feature/archive/keller.shtml http://www.sappublications.com/insider/article.htm?key=20248

ABAP Objects, Introduction: ISBN 0-201-75080-5 (English) ISBN 3-89842-147-3 (German) ABAP Objects, Reference: ISBN 1-59229-011-6 (English) ISBN 3-934358-61-6 (German)  SAP AG2003, TechED_Basel / ABAP256, Horst Keller, Stefan Bresch / 84

Questions?


Feedback

Please complete your session evaluation and drop it in the box on your way out.

The SAP TechEd ’03 Basel Team


Why Use ABAP Object by Horst Keller

Recommend Documents