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Managing Persistent Objects With Object Services |
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Written by Dany Charbonneau
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Sunday, 27 May 2007 |
Managing persistent objects with object services.
Note: This only works for WAS 6.10 and over.
There is a way to avoid building a fully object-oriented program while still working with non-object-oriented relational database. The object services layer now provides a persistence framework that closes the object-relational gap. You no longer need to write SQL code as objects are transparently loaded from the database when needed. You must create a persistent class.
Choose transaction SE24 and create a persistent class; this class must be protected.
In the class builder, a new button is added in the main toolbar, press it : 
in the next screen, you just have to map which fields you need in your persistent class
After having saved the previous screen, you will notice that the system creates a set/get method for each field that you selected.
Activate the whole class. Now that we have a persistent object to access the database table SFLIGHT, we must access it in a program. Here is a small example to read/write data into SFLIGHT using persistent objects.
Code: REPORT zdany_sflight_persistent.
DATA : l_flight TYPE REF TO zcl_dany_sflight,
l_flight_agent TYPE REF TO zca_dany_sflight,
l_seatsfree TYPE i,
l_seatsocc TYPE i.
* Reference to the class agent, ALWAYS required for any operation
l_flight_agent = zca_dany_sflight=>agent.
TRY.
*We read a record from SFLIGHT using a unique key
l_flight = l_flight_agent->get_persistent(
i_carrid = 'LH'
i_connid = '0400'
i_fldate = '20031030' ).
*We read a specific field
l_seatsfree = l_flight->get_seatsmax( ) - l_flight->get_seatsocc( ).
IF l_seatsfree > 0.
l_seatsocc = l_flight->get_seatsocc( ) + 1.
* We write back a specific field into the DB
l_flight->set_seatsocc( l_seatsocc ).
ENDIF.
ENDTRY.
COMMIT WORK. There are lots of other methods and techniques that you can use in persistent classes.
A demonstration of this can be found in program DEMO_CREATE_PERSISTENT.
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