Design Patterns in Object-oriented ABAP

If a proven solution for a recurring problem already exists, why would you reinvent the wheel? This hands-on programming tutorial explains why and how you can use design patterns to help complete your ABAP tasks in less time with better code. Step-by-step, the author guides you through class and interface definitions, as well as the coding for all relevant methods. Plus, benefit immediately from extensively commented real-world code that shows how to implement MVC, Facade, Adapter, Decorator, and more in ABAP Objects. Implementation of Design Patterns Follow the implementation of Singleton, Adapter, Factory, MVC, Facade, Composite, and Decorator in ABAP. Hands-on Approach Written for practitioners, the book includes lots of code, detailed UML diagrams, and comprehensive explanations that guarantee quick success. Real-World Demo Application The code in this book is not just theory it's taken from a real-world application that implements all patterns shown in a production environment. Improving Code This book helps you improve the robustness and extendibility of your ABAP Objects code, while reducing maintenance efforts.New Coverage of Web Dynpro and the Factory Pattern This second edition has been thoroughly revised and expanded including a new chapter on the Factory pattern, and an extensive section on MVC implementation in multi-technology development for SAP GUI and Web Dynpro ABAP.

Table of Contents:
1 Introduction 11 1.1 What are Design Patterns? 12 1.2 Communication in Design Patterns 13 1.3 Design Patterns in Software Design 14 1.4 Success Story: The Project and Its By-Product 15 1.5 Formatting and Naming Conventions 17 1.6 Prerequisites 18 1.6.1 Basics of Object-Oriented Software Design 18 1.6.2 Experience in ABAP Programming 18 1.6.3 Web Dynpro ABAP 18 1.6.4 Reading Unified Modeling Language (UML) Diagrams 19 1.7 Structure of the Book 25 2 The Demo Application 29 2.1 Demo Application Server Version Compatibility 31 2.2 Object Orientation 32 2.3 Demo Application at Work 32 2.3.1 The Command Tree 33 2.3.2 Table Maintenance Functionalities 34 2.3.3 Single-record Maintenance Functionalities 36 2.3.4 Empty Containers 36 2.3.5 Special Function: Comments for Flight Schedules 37 2.4 Application Model 38 2.5 SAP GUI Application Controller 41 2.6 Web Dynpro Application Controller 42 2.7 Running the Application While Reading 44 2.8 Summary 45 3 The Singleton Pattern 47 3.1 Case-Study Problem: Running Main Program Only Once 48 3.2 Singleton in the Application Model 50 3.3 Summary 51 4 The Adapter Pattern 53 4.1 Case-Study Problem: Application with a Command Tree 53 4.2 The Adapter in the Demo Application 55 4.3 Interface ZIF_DPD_TREE_OBJECT 55 4.3.1 Types 56 4.3.2 Attributes 56 4.3.3 Constants 57 4.3.4 get_sub_objects Method 58 4.3.5 get_attribute Method 58 4.3.6 get_commands Method 59 4.3.7 user_command Method 61 4.4 Usage of the ZIF_DPD_TREE_OBJECT Interface 61 4.4.1 Active Objects Storage in the Application Model 61 4.4.2 Expanding Tree Nodes 62 4.4.3 Reacting to User's Node Selection 62 4.4.4 Creating Command Buttons 63 4.4.5 Responding to Command Buttons 63 4.5 Summary 64 5 The Factory Pattern 65 5.1 Real-Life Example 67 5.2 Case-Study Problem: Docking Containers Orderly Arranged 67 5.3 Class ZCL_DPD_DOCK_CONTAINER_FACTORY 69 5.3.1 Attributes 70 5.3.2 get_container Method 71 5.3.3 destroy_container Method 71 5.3.4 hide_all and unhide_all Methods 72 5.3.5 refresh_total_size Method 73 5.3.6 resize_containers Method 74 5.3.7 Usage of the Container Factory Class 76 5.4 Summary 77 6 The Model-View-Controller (MVC) Pattern 79 6.1 Two MVCs in the Demo Application 81 6.2 Case-Study Problem I: Single Application in Different UI Technologies 83 6.3 Case-Study Problem II: SAP GUI Displaying Table Data in Different Controls 84 6.4 The Application Model: Class ZCL_DPD_APP_MOD 86 6.4.1 Attributes 87 6.4.2 constructor Method 88 6.4.3 get_app_mod Method 89 6.4.4 get_tree_object Method 89 6.4.5 get_tree_objects Method 90 6.4.6 add_tree_objects Method 90 6.5 Class ZCL_DPD_MOD_DBT 91 6.5.1 Interfaces 91 6.5.2 Attributes 91 6.5.3 constructor Method 93 6.5.4 zif_dpd_tree_object~user_command Method 94 6.5.5 refresh Method 94 6.5.6 save Method 95 6.5.7 zif_dpd_tree_object~get_sub_objects Method 95 6.5.8 zif_dpd_tree_object~get_attribute Method 96 6.5.9 zif_dpd_tree_object~get_commands Method 96 6.6 Class lcl_mod_dbt_carriers 97 6.6.1 Definition 97 6.6.2 constructor Method 98 6.6.3 zif_dpd_tree_object~get_sub_objects method 99 6.7 Other lcl_mod_* classes 100 6.8 Controller 1: The Program ZDPD_APP_CON_GUI 100 6.9 Class lcl_main_program 102 6.9.1 Definition 102 6.9.2 Attributes 103 6.9.3 run_main_program Method 103 6.9.4 constructor Method 104 6.9.5 on_double_click Method 106 6.9.6 on_expand_no_children Method 109 6.9.7 on_menu_request Method 110 6.9.8 on_menu_select Method 110 6.10 Class lcl_con_alv 111 6.10.1 Definition 111 6.10.2 alv Attribute 112 6.10.3 container Attribute 112 6.10.4 mo_model Attribute 113 6.10.5 Other Attributes 113 6.10.6 constructor Method 113 6.10.7 on_toolbar Method 116 6.10.8 on_user_command Method 117 6.10.9 free Method 118 6.10.10 get_fcat Method 118 6.10.11 flight_schedule_st_text_edit Method 119 6.11 Class lcl_con_dd 121 6.11.1 Definition 121 6.11.2 mo_dd Attribute 122 6.11.3 Other attributes 122 6.11.4 constructor Method 122 6.11.5 on_clicked Method 123 6.11.6 refresh_display Method 124 6.11.7 free Method 128 6.12 Dynpro Screen: An Alien in All-Objects Program 129 6.12.1 Global Program Variables 129 6.12.2 Main Screen 0100 129 6.12.3 Two GUI Statuses 131 6.12.4 MODULE s0100_start 132 6.12.5 Subscreen 0200 an Empty Default Subscreen 132 6.12.6 Subscreen 0201 Carrier Details 133 6.13 Class lcl_con_dynpro_screen 135 6.13.1 Definition 136 6.13.2 mt_scr_contr Attribute 137 6.13.3 m_title, mo_model and mdt_outtab Attributes 137 6.13.4 m_dynnr_main and m_gui_status_main Attributes 137 6.13.5 create_controller Method 138 6.13.6 constructor Method 138 6.13.7 class_pai Method 139 6.13.8 class_pbo Method 140 6.13.9 pai Method 140 6.13.10 pbo Method 141 6.14 The Controller 2: Web Dynpro Component ZDPD_APP_CON_WEBDYNPRO 142 6.14.1 The ZDPD_APP_CON_WEBDYNPRO's COMPONENTCONTROLLER 143 6.14.2 Window MAIN_WINDOW 148 6.14.3 View MAIN_VIEW 149 6.14.4 View ALV_GRID_VIEW 154 6.15 Summary 165 6.16 Appendix: Process Open Object Close Object 166 7 The Facade Pattern 171 7.1 Case-Study Problem: Editing Comments on Each Flight Schedule 174 7.1.1 Specific Aspects of the Standard Text Editor 178 7.1.2 Starting point: ZIF_DPD_TREE_object~GET_COMMANDS Method 178 7.2 Class ZCL_DPD_ST_TEXT_EDITOR 179 7.2.1 Attributes 180 7.2.2 Methods 180 7.2.3 show Method 181 7.2.4 on_toolbar_func_sel Method 186 7.2.5 save Method 186 7.2.6 free Method 188 7.3 Facade in Web Dynpro 188 7.4 Summary 188 8 The Composite Pattern 191 8.1 Case-Study Problem: Organizing Flights by Date 194 8.2 Class lcl_mod_dbt_flights 196 8.2.1 Definition 197 8.2.2 Attributes 198 8.2.3 constructor Method 199 8.2.4 zif_dpd_tree_object~get_sub_objects Method 205 8.3 Summary 209 9 The Decorator Pattern 211 9.1 Case-Study Problem: Lookup Data for Internal Tables 213 9.2 Class ZCL_DPD_ITAB_DEC 218 9.2.1 Attributes 218 9.2.2 Public Class' Types 221 9.2.3 constructor Method 222 9.2.4 refresh_data Method 223 9.2.5 get_fields Method 223 9.3 Class ZCL_DPD_ITAB_DEC_AIRPORTS 224 9.3.1 Attribute 225 9.3.2 refresh_data Method 225 9.3.3 get_fields Method 228 9.4 Class lcl_itab_dec_fl_sched_comment 231 9.4.1 Definition 232 9.4.2 Attributes 232 9.4.3 get_fields Method 232 9.5 Other Decorators in the Application 234 9.6 Implementation of the Decorator Pattern in the Application 235 9.7 Summary 236 10 Summary 237 10.1 Examples of Extension 237 10.1.1 New Table-Maintaining Object at the Tree Airplanes 238 10.1.2 New Dynpro Screen: Airplane Details 239 10.1.3 Authorization Checks 243 10.1.4 Toggle Display/Edit 244 10.1.5 Locking Mechanism for Multiuser Applications 245 10.2 Benefits of Combining Objects with DPs 245 10.3 Closing Word by the Author 247 The Author 249 Index 251

About the Author :
Igor Barbaric is a software-development specialist with seven years of experience in development for SAP solutions (ABAP) and Microsoft products (Access, Excel), in system integration (SAP-MS products and SAP-Java), and in SAP system administration. He worked as a team member on several international projects. He was a speaker at the SDN Meets Labs (Walldorf/Rot, 2005) and SAP TechEd (Vienna, 2005), with a session titled Design Patterns in Object-Oriented ABAP.