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This blog represents part 4 of the 6-part series Getting comfortable using the Object-Oriented design model with ABAP.

Part 1 – Transforming a simple procedural model into its equivalent OO design, focusing on the OO principles of Encapsulation and Abstraction.


Part 2 – Exploring Abstraction further by refactoring the program to transform selected static classes into instantiable classes.


Part 3 – Refactoring the program further to take advantage of the OO principle of Inheritance.


Part 4 – Adhering to the Single Responsibility Principle by refining the program to restrict each class to do only what it is intended to do.


Part 5 – Removing classes that no longer serve a purpose.


Part 6 – Introducing the Singleton OO design pattern, resulting in elimination of all static classes.


To recap from the preceding blog, we took a program having duplication of code amongst three report classes and consolidated that duplicated code, making it available to the three classes through the use of Inheritance. Here is the source code as we left it in the previous blog:
report.
interface data_exchangeable.
types : row_counter type n length 02.
types : email_recipient
type adr6-smtp_addr.
endinterface.
class excel_spreadsheet_manager definition
final.
public section.
methods : copy_table_to_excel_worksheet
importing
source_stack
type standard table
source_description
type string
raising
zcx_excel
, send_excel_via_email
importing
recipient
type data_exchangeable=>email_recipient
.
private section.
data : excel type ref to zcl_excel.
endclass.
class excel_spreadsheet_manager implementation.
method copy_table_to_excel_worksheet.
constants : first_column type char1 value 'A'
.
data : worksheet type ref to zcl_excel_worksheet
, worksheet_title
type zexcel_sheet_title
, table_settings type zexcel_s_table_settings
.
table_settings-table_style = zcl_excel_table=>builtinstyle_medium2.
table_settings-show_row_stripes
= abap_true.
table_settings-nofilters = abap_true.
table_settings-top_left_column
= first_column.
table_settings-top_left_row = 01.
if excel is not bound.
create object excel.
worksheet = excel->get_active_worksheet( ).
else.
worksheet = excel->add_new_worksheet( ).
endif.
worksheet_title = source_description.
worksheet->set_title( worksheet_title ).
worksheet->bind_table(
ip_table = source_stack
is_table_settings = table_settings
).
endmethod.
method send_excel_via_email.
constants : excel_file_type
type string value '.xlsx'
, file_name_parameter
type string value '&SO_FILENAME='
.
data : excel_writer type ref to zif_excel_writer
, excel_as_xstring
type xstring
, excel_as_xstring_bytecount
type i
, excel_as_solix_stack
type solix_tab
, mail_send_request
type ref to cl_bcs
, mail_message type ref to cl_document_bcs
, any_bcs_exception
type ref to cx_bcs
, diagnostic type string
, mail_title type so_obj_des
, mail_text_stack
type soli_tab
, mail_text_entry
like line
of mail_text_stack
, mail_attachment_subject
type sood-objdes
, mail_attachment_bytecount
type sood-objlen
, mail_attachment_header_stack
type soli_tab
, mail_attachment_header_entry
like line of mail_attachment_header_stack
, internet_email_recipient
type ref to if_recipient_bcs
, successful_send
type abap_bool
, file_name type string
.
" Much of the code here was lifted from method send_mail of
" class lcl_ouput, defined in object ZDEMO_EXCEL_OUTPUTOPT_INCL:
concatenate sy-repid " this report name
sy-datum " current date
sy-uzeit " current time
excel_file_type " excel file extension
into file_name.
mail_title = file_name.
mail_attachment_subject = file_name.
mail_text_entry = 'See attachment'.
append mail_text_entry
to mail_text_stack.
concatenate file_name_parameter
file_name
into mail_attachment_header_entry.
append mail_attachment_header_entry
to mail_attachment_header_stack.
create object excel_writer type zcl_excel_writer_2007.
excel_as_xstring = excel_writer->write_file( excel ).
excel_as_solix_stack = cl_bcs_convert=>xstring_to_solix( iv_xstring = excel_as_xstring ).
excel_as_xstring_bytecount = xstrlen( excel_as_xstring ).
mail_attachment_bytecount = excel_as_xstring_bytecount.
try.
mail_message = cl_document_bcs=>create_document(
i_type = 'RAW' "#EC NOTEXT
i_text = mail_text_stack
i_subject = mail_title
).
mail_message->add_attachment(
i_attachment_type = 'XLS' "#EC NOTEXT
i_attachment_subject = mail_attachment_subject
i_attachment_size = mail_attachment_bytecount
i_att_content_hex = excel_as_solix_stack
i_attachment_header = mail_attachment_header_stack
).
mail_send_request = cl_bcs=>create_persistent( ).
mail_send_request->set_document( mail_message ).
internet_email_recipient = cl_cam_address_bcs=>create_internet_address( recipient ).
mail_send_request->add_recipient( internet_email_recipient ).
successful_send = mail_send_request->send( ).
commit work.
if successful_send eq abap_false.
message i500(sbcoms) with recipient.
else.
message s022(so).
message 'Document ready to be sent - Check SOST' type 'I'.
endif.
catch cx_bcs into any_bcs_exception.
diagnostic = any_bcs_exception->if_message~get_text( ).
message diagnostic type 'I'.
endtry.
endmethod.
endclass.
class report definition
abstract.
public section.
methods : produce_report abstract
importing
row_count
type data_exchangeable=>row_counter
excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
raising
zcx_excel
.
protected section.
methods : present_report
changing
record_stack
type standard table
.
endclass.
class report implementation.
method present_report.
data : alv_report type ref to cl_salv_table
.
try.
call method cl_salv_table=>factory
importing
r_salv_table = alv_report
changing
t_table = record_stack.
catch cx_salv_msg.
return.
endtry.
alv_report->display( ).
endmethod.
endclass.
class flight_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class flight_report implementation.
method produce_report.
data : flight_stack type standard table of sflight
.
select *
into table flight_stack
from sflight
up to row_count rows.
call method me->present_report
changing
record_stack = flight_stack.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = flight_stack
source_description = 'Flights'.
endmethod.
endclass.
class carrier_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class carrier_report implementation.
method produce_report.
data : carrier_stack type standard table of scarr
.
select *
into table carrier_stack
from scarr
up to row_count rows.
call method me->present_report
changing
record_stack = carrier_stack.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = carrier_stack
source_description = 'Carriers'.
endmethod.
endclass.
class booking_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class booking_report implementation.
method produce_report.
data : booking_stack type standard table of sbook
.
select *
into table booking_stack
from sbook
up to row_count rows.
call method me->present_report
changing
record_stack = booking_stack.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = booking_stack
source_description = 'Bookings'.
endmethod.
endclass.
class process_driver definition
abstract
final.
public section.
class-methods: drive_process
importing
row_count
type data_exchangeable=>row_counter
recipient
type data_exchangeable=>email_recipient
.
endclass.
class process_driver implementation.
method drive_process.
data : flight_report type ref to flight_report
, carrier_report type ref to carrier_report
, booking_report type ref to booking_report
, excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
.
create object: flight_report
, carrier_report
, booking_report
, excel_spreadsheet_manager
.
try.
call method flight_report->produce_report exporting row_count = row_count
excel_spreadsheet_manager = excel_spreadsheet_manager.
call method carrier_report->produce_report exporting row_count = row_count
excel_spreadsheet_manager = excel_spreadsheet_manager.
call method booking_report->produce_report exporting row_count = row_count
excel_spreadsheet_manager = excel_spreadsheet_manager.
catch zcx_excel ##NO_HANDLER.
endtry.
call method excel_spreadsheet_manager->send_excel_via_email exporting recipient = recipient.
endmethod.
endclass.
class email_address_resolver definition
abstract
final.
public section.
class-methods: resolve_email_address
importing
userid
type syuname
exporting
email_address
type data_exchangeable=>email_recipient
.
endclass.
class email_address_resolver implementation.
method resolve_email_address.
select single smtp_addr
into email_address
from adr6 ##WARN_OK
inner join
usr21 on usr21~persnumber eq adr6~persnumber
where usr21~bname eq userid.
endmethod.
endclass.
parameters : rowcount type data_exchangeable=>row_counter.
parameters : recipien type data_exchangeable=>email_recipient.
initialization.
call method email_address_resolver=>resolve_email_address
exporting
userid = sy-uname
importing
email_address = recipien.
start-of-selection.
call method process_driver=>drive_process
exporting
row_count = rowcount
recipient = recipien.

Open your favorite ABAP editor, make a copy of this ABAP program and follow along as we apply changes to classes having multiple responsibilities and transform them into classes that adhere to the Single Responsibility Principle. For those who do not have ABAP2XLSX available at their site, replace class excel_spreadsheet_manager with the following source code:
class excel_spreadsheet_manager        definition
final.
public section.
methods : copy_table_to_excel_worksheet
importing
source_stack
type standard table
source_description
type string
raising
zcx_excel
, send_excel_via_email
importing
recipient
type data_exchangeable=>email_recipient
.
private section.
data : excel type string.
endclass.
class excel_spreadsheet_manager implementation.
method copy_table_to_excel_worksheet.
data : source_stack_lines type string.
describe table source_stack lines source_stack_lines.
concatenate excel
source_stack_lines
source_description
into excel separated by space.
endmethod.
method send_excel_via_email.
data : message type string.
concatenate excel
'would be sent to'
recipient
into message separated by space.
message message type 'I'.
endmethod.
endclass.

and include the following local exception class definition after the report statement:
class zcx_excel                        definition
inheriting from cx_static_check.
endclass.

Motivation

It’s one thing to understand the object-oriented design principles Encapsulation, Abstraction and Inheritance, and to use them effectively in our programming efforts as we’ve done so far with our example program. It is quite another to learn the lessons of software maintenance that have been discovered by pioneers of object-oriented programming. One of these pioneers is Robert C. Martin (https://en.wikipedia.org/wiki/Robert_C._Martin), whose experience with software maintenance led him to define the SOLID principles (https://en.wikipedia.org/wiki/SOLID), which are:

  • Single Responsibility Principle

  • Open-Closed Principle

  • Liskov Substitution Principle

  • Interface Segregation Principle

  • Dependency Inversion Principle


Known affectionately in the software industry as Uncle Bob, he defined the SOLID principles in his 2000 paper titled Design Principles and Design Patterns (http://www.cvc.uab.es/shared/teach/a21291/temes/object_oriented_design/materials_adicionals/principl...). These are known as the SOLID principles due to the first letter of each principle building the acronym SOLID. The SOLID principles have been embraced by many scholars of object-oriented design as good advice for keeping object-oriented software flexible and maintainable. For now, we are going to focus on the first of these principles: the Single Responsibility Principle.

Single Responsibility Principle

According to the Principles of Object-Oriented Design (http://www.butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod), the Single Responsibility Principle states:

  • A class should have one, and only one, reason to change.


Currently our flight_report, carrier_report and booking_report classes all perform similar processing:

  • Get from its respective persistence repository the number of records indicated by the user

  • Display these records in an ALV report

  • Arrange for these records to be captured in a worksheet of an Excel spreadsheet


As you can see, these report classes do more than just report – each class has the responsibility for each of the three bullet points noted above, only the second of which involves anything related to reporting. Accordingly, these classes run afoul of the Single Responsibility Principle – each one is doing more than its class name suggests it should have the responsibility to do.

Eliminating multiple responsibilities – step 1

Let’s change the program so that these classes have only a single responsibility. The first thing we’ll do is to remove from these classes the responsibility to retrieve records to be presented in the report. Define a new static class called flight_records_retriever using the skeleton class shown below, placing this new class immediately after the endinterface statement.
class flight_records_retriever         definition
abstract
final.
public section.
types : record_list type standard table of sflight.
class-methods: retrieve_records
importing
row_count
type data_exchangeable=>row_counter
exporting
record_stack
type flight_records_retriever=>record_list
.
endclass.
class flight_records_retriever implementation.
method retrieve_records.
endmethod.
endclass.

At this point a syntax check should pass. Now make the following changes:

  • Move the select statement from method produce_report of class flight_report into the new retrieve records statement, replacing actual parameter flight_stack with record_stack.

  • Replace the removed lines from method produce_report with a call to this new method, as in:


    call method flight_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = flight_stack.

At this point a syntax check should pass. This change does not completely resolve the problem of the flight_report still being responsible for retrieving the records it presents in its report, but this is the first step in reaching that goal.

Next, make the same relative changes to classes carrier_report and booking_report as were made for class flight_report, including the creation of two new respective classes called carrier_records_retriever and booking_records_retriever, placing each new class ahead of class excel_spreadsheet_manager.

At this point a syntax check should pass. Executing the program at this point should prove that it still works as before.

Eliminating multiple responsibilities – step 2

Next, change the signature of method produce_report of class report so that:

  • It no longer accepts importing parameter row_count.

  • It now accepts a changing parameter named record_stack, defined as type standard table.


After applying these changes the definition of the method should look like this:
    methods      : produce_report abstract
importing
excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
changing
record_stack
type standard table
raising
zcx_excel
.

A syntax check will fail now in method produce_report of class flight_report due to the reference to parameter row_count, which no longer is defined in the signature of this method. Change this method in the following ways:

  • Move the data statement to precede the create object statement in method drive_process of class process_driver, changing its type to indicate not standard table of sflight but instead type flight_records_retriever=>record_list.

  • Move the call to method retrieve_records of class flight_records_retriever to follow the create object statement in method drive_process of class process_driver.

  • For the formal parameter record_stack used with the call to method present_report, change the actual parameter from flight_stack to record_stack.

  • For the formal parameter source_stack used with the call to method copy_table_to_excel_worksheet of class excel_spreadsheet_manager, change the actual parameter from flight_stack to record_stack.


Afterward, the code in method produce_report of class flight_report should look like this:
  method produce_report.
call method me->present_report
changing
record_stack = record_stack.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = record_stack
source_description = 'Flights'.
endmethod.

Next, make the same relative changes to classes carrier_report and booking_report as were made for class flight_report.

Then in method drive_process of class process_driver, change the three call method statements following the try statement so that each one:

  • no longer has an exporting parameter for row_count

  • has a changing parameter for formal parameter record_stack whose actual parameter is flight_stack, carrier_stack and booking_stack, respectively


When completed, method drive_process should look like this:
  method drive_process.
data : flight_report type ref to flight_report
, carrier_report type ref to carrier_report
, booking_report type ref to booking_report
, excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
, flight_stack type flight_records_retriever=>record_list
, carrier_stack type carrier_records_retriever=>record_list
, booking_stack type booking_records_retriever=>record_list
.
create object: flight_report
, carrier_report
, booking_report
, excel_spreadsheet_manager
.
call method flight_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = flight_stack.
call method carrier_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = carrier_stack.
call method booking_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = booking_stack.
try.
call method flight_report->produce_report exporting excel_spreadsheet_manager = excel_spreadsheet_manager
changing record_stack = flight_stack.
call method carrier_report->produce_report exporting excel_spreadsheet_manager = excel_spreadsheet_manager
changing record_stack = carrier_stack.
call method booking_report->produce_report exporting excel_spreadsheet_manager = excel_spreadsheet_manager
changing record_stack = booking_stack.
catch zcx_excel ##NO_HANDLER.
endtry.
call method excel_spreadsheet_manager->send_excel_via_email exporting recipient = recipient.
endmethod.

At this point a syntax check will pass. Now none of the produce_report methods of classes flight_report, carrier_report and booking_report remain responsible for retrieving the records each one presents in its corresponding ALV report. Instead, method drive_process of class process_driver now assumes the responsibility for retrieving these records and passing them to the produce_report methods.

Executing the program at this point should prove that it still works as before.

Eliminating multiple responsibilities – step 3

Whereas our produce_report methods no longer retrieve the records they present in the ALV report they produce, these methods still retain the responsibility for sending those records to be converted to a worksheet of an Excel spreadsheet, so let’s also make these corrections.

First, change the signature of method produce_report in class report so that it no longer imports an instance of an excel_spreadsheet_manager and no longer indicates that it can raise exception zcx_excel.

At this point the syntax check fails in method produce_report of class flight_report on the call to method copy_table_to_excel_worksheet. Move this call method statement from method produce_report of class flight_report into method drive_process of class process_driver, placing it immediately before the catch clause of the try-endtry block and changing its actual parameter from record_stack to flight_stack.

Next, make the same relative changes to classes carrier_report and booking_report as were made for class flight_report.

Finally, in method drive_process of class process_driver, remove the exporting parameters from the three calls to the produce_report methods.

At this point a syntax check passes, but the three calls to method produce_report within the try-entry block of method driver_process no longer can raise the exception zcx_excel, so these statements should be moved ahead of the corresponding try statement. When completed, method drive_process should look like this:
  method drive_process.
data : flight_report type ref to flight_report
, carrier_report type ref to carrier_report
, booking_report type ref to booking_report
, excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
, flight_stack type flight_records_retriever=>record_list
, carrier_stack type carrier_records_retriever=>record_list
, booking_stack type booking_records_retriever=>record_list
.
create object: flight_report
, carrier_report
, booking_report
, excel_spreadsheet_manager
.
call method flight_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = flight_stack.
call method carrier_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = carrier_stack.
call method booking_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = booking_stack.
call method flight_report->produce_report changing record_stack = flight_stack.
call method carrier_report->produce_report changing record_stack = carrier_stack.
call method booking_report->produce_report changing record_stack = booking_stack.
try.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = flight_stack
source_description = 'Flights'.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = carrier_stack
source_description = 'Carriers'.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = booking_stack
source_description = 'Bookings'.
catch zcx_excel ##NO_HANDLER.
endtry.
call method excel_spreadsheet_manager->send_excel_via_email exporting recipient = recipient.
endmethod.

Now none of the produce_report methods of classes flight_report, carrier_report and booking_report remain responsible for insuring that the records it uses to create the ALV report also are copied to an Excel worksheet. Instead, method drive_process of class process_driver now assumes this responsibility.

Executing the program at this point should prove that it still works as before.

Summary

We’ve made enough changes for now and the final image of the code looks like this:
report.
interface data_exchangeable.
types : row_counter type n length 02.
types : email_recipient
type adr6-smtp_addr.
endinterface.
class flight_records_retriever definition
abstract
final.
public section.
types : record_list type standard table of sflight.
class-methods: retrieve_records
importing
row_count
type data_exchangeable=>row_counter
exporting
record_stack
type flight_records_retriever=>record_list
.
endclass.
class flight_records_retriever implementation.
method retrieve_records.
select *
into table record_stack
from sflight
up to row_count rows.
endmethod.
endclass.
class carrier_records_retriever definition
abstract
final.
public section.
types : record_list type standard table of scarr.
class-methods: retrieve_records
importing
row_count
type data_exchangeable=>row_counter
exporting
record_stack
type carrier_records_retriever=>record_list
.
endclass.
class carrier_records_retriever implementation.
method retrieve_records.
select *
into table record_stack
from scarr
up to row_count rows.
endmethod.
endclass.
class booking_records_retriever definition
abstract
final.
public section.
types : record_list type standard table of sbook.
class-methods: retrieve_records
importing
row_count
type data_exchangeable=>row_counter
exporting
record_stack
type booking_records_retriever=>record_list
.
endclass.
class booking_records_retriever implementation.
method retrieve_records.
select *
into table record_stack
from sbook
up to row_count rows.
endmethod.
endclass.
class excel_spreadsheet_manager definition
final.
public section.
methods : copy_table_to_excel_worksheet
importing
source_stack
type standard table
source_description
type string
raising
zcx_excel
, send_excel_via_email
importing
recipient
type data_exchangeable=>email_recipient
.
private section.
data : excel type ref to zcl_excel.
endclass.
class excel_spreadsheet_manager implementation.
method copy_table_to_excel_worksheet.
constants : first_column type char1 value 'A'
.
data : worksheet type ref to zcl_excel_worksheet
, worksheet_title
type zexcel_sheet_title
, table_settings type zexcel_s_table_settings
.
table_settings-table_style = zcl_excel_table=>builtinstyle_medium2.
table_settings-show_row_stripes
= abap_true.
table_settings-nofilters = abap_true.
table_settings-top_left_column
= first_column.
table_settings-top_left_row = 01.
if excel is not bound.
create object excel.
worksheet = excel->get_active_worksheet( ).
else.
worksheet = excel->add_new_worksheet( ).
endif.
worksheet_title = source_description.
worksheet->set_title( worksheet_title ).
worksheet->bind_table(
ip_table = source_stack
is_table_settings = table_settings
).
endmethod.
method send_excel_via_email.
constants : excel_file_type
type string value '.xlsx'
, file_name_parameter
type string value '&SO_FILENAME='
.
data : excel_writer type ref to zif_excel_writer
, excel_as_xstring
type xstring
, excel_as_xstring_bytecount
type i
, excel_as_solix_stack
type solix_tab
, mail_send_request
type ref to cl_bcs
, mail_message type ref to cl_document_bcs
, any_bcs_exception
type ref to cx_bcs
, diagnostic type string
, mail_title type so_obj_des
, mail_text_stack
type soli_tab
, mail_text_entry
like line
of mail_text_stack
, mail_attachment_subject
type sood-objdes
, mail_attachment_bytecount
type sood-objlen
, mail_attachment_header_stack
type soli_tab
, mail_attachment_header_entry
like line of mail_attachment_header_stack
, internet_email_recipient
type ref to if_recipient_bcs
, successful_send
type abap_bool
, file_name type string
.
" Much of the code here was lifted from method send_mail of
" class lcl_ouput, defined in object ZDEMO_EXCEL_OUTPUTOPT_INCL:
concatenate sy-repid " this report name
sy-datum " current date
sy-uzeit " current time
excel_file_type " excel file extension
into file_name.
mail_title = file_name.
mail_attachment_subject = file_name.
mail_text_entry = 'See attachment'.
append mail_text_entry
to mail_text_stack.
concatenate file_name_parameter
file_name
into mail_attachment_header_entry.
append mail_attachment_header_entry
to mail_attachment_header_stack.
create object excel_writer type zcl_excel_writer_2007.
excel_as_xstring = excel_writer->write_file( excel ).
excel_as_solix_stack = cl_bcs_convert=>xstring_to_solix( iv_xstring = excel_as_xstring ).
excel_as_xstring_bytecount = xstrlen( excel_as_xstring ).
mail_attachment_bytecount = excel_as_xstring_bytecount.
try.
mail_message = cl_document_bcs=>create_document(
i_type = 'RAW' "#EC NOTEXT
i_text = mail_text_stack
i_subject = mail_title
).
mail_message->add_attachment(
i_attachment_type = 'XLS' "#EC NOTEXT
i_attachment_subject = mail_attachment_subject
i_attachment_size = mail_attachment_bytecount
i_att_content_hex = excel_as_solix_stack
i_attachment_header = mail_attachment_header_stack
).
mail_send_request = cl_bcs=>create_persistent( ).
mail_send_request->set_document( mail_message ).
internet_email_recipient = cl_cam_address_bcs=>create_internet_address( recipient ).
mail_send_request->add_recipient( internet_email_recipient ).
successful_send = mail_send_request->send( ).
commit work.
if successful_send eq abap_false.
message i500(sbcoms) with recipient.
else.
message s022(so).
message 'Document ready to be sent - Check SOST' type 'I'.
endif.
catch cx_bcs into any_bcs_exception.
diagnostic = any_bcs_exception->if_message~get_text( ).
message diagnostic type 'I'.
endtry.
endmethod.
endclass.
class report definition
abstract.
public section.
methods : produce_report abstract
changing
record_stack
type standard table
.
protected section.
methods : present_report
changing
record_stack
type standard table
.
endclass.
class report implementation.
method present_report.
data : alv_report type ref to cl_salv_table
.
try.
call method cl_salv_table=>factory
importing
r_salv_table = alv_report
changing
t_table = record_stack.
catch cx_salv_msg.
return.
endtry.
alv_report->display( ).
endmethod.
endclass.
class flight_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class flight_report implementation.
method produce_report.
call method me->present_report
changing
record_stack = record_stack.
endmethod.
endclass.
class carrier_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class carrier_report implementation.
method produce_report.
call method me->present_report
changing
record_stack = record_stack.
endmethod.
endclass.
class booking_report definition
final
inheriting from report.
public section.
methods : produce_report redefinition
.
endclass.
class booking_report implementation.
method produce_report.
call method me->present_report
changing
record_stack = record_stack.
endmethod.
endclass.
class process_driver definition
abstract
final.
public section.
class-methods: drive_process
importing
row_count
type data_exchangeable=>row_counter
recipient
type data_exchangeable=>email_recipient
.
endclass.
class process_driver implementation.
method drive_process.
data : flight_report type ref to flight_report
, carrier_report type ref to carrier_report
, booking_report type ref to booking_report
, excel_spreadsheet_manager
type ref to excel_spreadsheet_manager
, flight_stack type flight_records_retriever=>record_list
, carrier_stack type carrier_records_retriever=>record_list
, booking_stack type booking_records_retriever=>record_list
.
create object: flight_report
, carrier_report
, booking_report
, excel_spreadsheet_manager
.
call method flight_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = flight_stack.
call method carrier_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = carrier_stack.
call method booking_records_retriever=>retrieve_records
exporting
row_count = row_count
importing
record_stack = booking_stack.
call method flight_report->produce_report changing record_stack = flight_stack.
call method carrier_report->produce_report changing record_stack = carrier_stack.
call method booking_report->produce_report changing record_stack = booking_stack.
try.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = flight_stack
source_description = 'Flights'.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = carrier_stack
source_description = 'Carriers'.
call method excel_spreadsheet_manager->copy_table_to_excel_worksheet
exporting
source_stack = booking_stack
source_description = 'Bookings'.
catch zcx_excel ##NO_HANDLER.
endtry.
call method excel_spreadsheet_manager->send_excel_via_email exporting recipient = recipient.
endmethod.
endclass.
class email_address_resolver definition
abstract
final.
public section.
class-methods: resolve_email_address
importing
userid
type syuname
exporting
email_address
type data_exchangeable=>email_recipient
.
endclass.
class email_address_resolver implementation.
method resolve_email_address.
select single smtp_addr
into email_address
from adr6 ##WARN_OK
inner join
usr21 on usr21~persnumber eq adr6~persnumber
where usr21~bname eq userid.
endmethod.
endclass.
parameters : rowcount type data_exchangeable=>row_counter.
parameters : recipien type data_exchangeable=>email_recipient.
initialization.
call method email_address_resolver=>resolve_email_address
exporting
userid = sy-uname
importing
email_address = recipien.
start-of-selection.
call method process_driver=>drive_process
exporting
row_count = rowcount
recipient = recipien.

We’ve changed the program so that none of the produce_report methods of classes flight_report, carrier_report and booking_report remain responsible for retrieving the records it uses to create the ALV report and none of these classes remain responsible for insuring that the records it uses to create the ALV report also are copied to an Excel worksheet. In short, the three classes flight_report, carrier_report and booking_report no longer have any responsibilities beyond producing a report, all three now complying with the Single Responsibility Principle.

What’s next?

There remain other concepts of object-oriented programming for us to explore using this simple example program. After removing the multiple responsibilities from the classes flight_report, carrier_report and booking_report, we now notice that all of these classes are identical to each other with the exception of their names. The next step is to refactor the program further to remove these duplicative classes. This will be covered in the blog representing part 5 of this 6-part series Getting comfortable using the Object-Oriented design model with ABAP.
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