Persistent Objects: A Quick reference

Objective

To store references to the persistent object persistently in the database.

Step: 1 -> Create a database table

This table should contain 2 fields of type OS_GUID in addition to the GUID object attribute. The first field is used to store the instance GUID while the other is used to store the class GUID.

Step: 2 ->Create a Persistent Class

In the next screen select the class type as Persistent Class and then hit Save Button.

Step: 3 -> Persistent Mapping or Mapping

Goto->Persistence Representation

Give the table name. For e.g. ZSTUDENT03 and hit the enter button

Table fields appear in the lower half of the tool screen. Double Click the table field and press the button. Add the remaining fields.

While adding the field INST_GUID choose the assignment type as Object reference and for the attribute type specify the class name for e.g. ZCL_PERSIST_03

To assign a class indicator, select the corresponding table field of type OS_GUID by double-clicking. Enter the name of the reference attribute for the attribute name.

Screen looks like below. Press Save.

Activate the Class. Press the Yes Button to activate the class actor as well.

Write a Program to create the persistent object.

Source Code excerpt:

DATA: AGENT TYPE REF TO ZCA_PERSIST_03,
     STUDENT TYPE REF TO ZCL_PERSIST_03,
     REF1 TYPE REF TO OBJECT.

DATA: SNO LIKE ZSTUDENT04-SNO VALUE '1000',
     SNAME LIKE ZSTUDENT04-SNAME VALUE 'HAKIM',
     MARK1 LIKE ZSTUDENT04-MARK1 VALUE '100',
     MARK2 LIKE ZSTUDENT04-MARK2 VALUE '100'.

AGENT = ZCA_PERSIST_03=>AGENT.

TRY.
CALL METHOD AGENT->CREATE_PERSISTENT
 EXPORTING
*    I_INST_GUID =
   I_MARK1     = MARK1
   I_MARK2     = MARK2
   I_SNAME     = SNAME
   I_SNO       = SNO
*  RECEIVING
*    RESULT      =
   .

 COMMIT WORK.
CATCH CX_OS_OBJECT_EXISTING .
ENDTRY.

Go to SE16 and check the entries.

Store the Persistent Object Reference in the database.

Source Code excerpt.

TRY.
CALL METHOD AGENT->IF_OS_CA_PERSISTENCY~GET_PERSISTENT_BY_OID
 EXPORTING
   I_OID  = '30EA9E25999F0843BE6F7B86063F2916'
 RECEIVING
   RESULT = REF1
   .
CATCH CX_OS_OBJECT_NOT_FOUND .
CATCH CX_OS_CLASS_NOT_FOUND .
ENDTRY.

STUDENT ?= REF1.
STUDENT->SET_INST_GUID( STUDENT ).
COMMIT WORK.

Go to SE16 and check the entries.