Wood J. Object-Oriented Programming with ABAP Objects

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Persistence Service Overview 11.2

media such as files. Irrespective of the underlying storage medium, you must use

an ABAP Dictionaiy object (i.e., a table, view, or structure) as the basis for your

mapping. The following list describes how various ABAP Dictionaiy objects can

be used to help you create your persistence maps:

• Single-table mapping

Most of

the

time, you will map the attributes of your persistent class to a single

ABAP Dictionary table. Here, you must map all of the fields from the table to

attributes in the persistent class. Of course, sometimes you may not want to

map all of the fields of

given table to your persistent class. For example, in a

large table with many fields, you might only be interested in a subset of fields

that have certain relevance to a particular usage scenario. In this case, you can

create a view that contains a subset of fields thatyou want to map and then use

the view to build your persistence mapping.

• Multiple-table mapping

It is also possible to map multiple tables onto a single persistent class. The only

requirement here is that each of the tables shares the exact same primaiy key.

At runtime, the Persistence Service is smart enough to connect the relevant

attributes used in the mapping with their associated tables so that the object

data is distributed across each of the tables correctly.

• Structure mappings

For more complex mappings, you can also use structure types. Structure types

are typically used to implement persistence mapping to files, and so on. How-

ever, they can also be used to map persistent classes that have a one-to-many

relationship to another persistent class type (e.g., a sales order and its line

items). Of course, because structure types do not refer to an actual database

table, the ORM tool will not be able to generate the code to persist the data.

Instead, you must implement your own logic for storing the persistent data in

persistent classes mapped from a structure.

11.2.3 Understanding the Class Agent API

After you finalize the persistence mapping for your class, the next step is to acti-

vate your changes in the Class Builder. Here, the Class Builder tool will use the

mapping details to construct the persistence class along with its associated agent

classes. The UML class diagram shown earlier in Figure 11.2 shows the relation-

ships between these classes. It also shows some of the more useful methods that

you can use to obtain and work with objects of your persistent class.

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11 | ABAP Object Services

For the most part, the names of the methods are pretty self-explanatoiy (e.g., you

use method CREATE_PERSISTENT to create a persistent object, etc.). However, the

generation of some of these methods varies depending upon the type of mapping

you chose to implement. For example, the base agent class CB_... will not have

methods GET_PERSISTENT and OELETE_PERSlSTENT if the persistent objects are not

managed by business keys. In this case, you must use methods implemented from

interfaces IF_0S_FACT0RY and 1F_0S_CA_PERSISTENCY instead.

You can find more information about these methods in the SAP online help doc-

umentation for ABAP Object Services

(http://help.sap.com).

You will also see some

concrete examples of these methods in Section 11.4, Working with Persistent

Objects.

11.3 Building Persistent Classes

At this point, you are probably eager to get started with some real-world exam-

ples. In the next several subsections, we will iteratively design a couple of persis-

tent classes to model a portion of

data model used to build an online course reg-

istration system. In particular, we will create two separate persistent classes called

ZCL_0S_PERS0N and ZCL_0S_ADDRESS, where instances of class ZCL_0S_PERS0N can

optionally have an instance of class ZCL_0S_ADDRESS associated with them. The

database tables upon which these persistent classes will be based are shown in

Figure 11.3 and Figure 11.4, respectively.

Transp Table ZCA_P£RS0N Active

Short Description £>r*ne Registration System Person

Attributes Delivery and Maintenance | Entry help/check CixrencyfOuanoty Fields

ximsFffl

Srch Help | Predefined T^pe

Field Key

in* Data element |OataTy Length Decim jShortDescrtplion

1AN0T

CLNT

©Client

6UIE

0 OS 60ID RAW 16

0Gioba»y Unique IdenMer

NAt1£ FIRST

•

AP NMEFIR

CHAR

©First name

IMC LAST

•

4C H*nELA$

CHAR

©Last name

CLASS

•

OS 6UID RAW 16

©Olobaty Unique IdenMer

ADDR REF

•

OS 6UID RAW 16

©Globafy Unique IdenMer

Figure 11.3 A8AP Dictionary Table Definition for Person Entity

286

Building Persistent Classes 11.3

Transp Table ZCA_AD©RESS Acftve

Short Description pnline Registration System Address

AtlnOuIes Delivery and Maintenance jMR

| Entry help/check

CurrencyOuantrty Fields

Tm m

SrchHelp | Predefined Type |

Field Key [Info Data element

DalaTy

Length lOecim jShortDescriplKin

KNOT

a 0

HAKQT

CIHT

©Client

jUIO

0 0

3S 6U1P

RAW

16) ©Globally unique identifier

5TREET1

• •

M> STREET CHAR

EO;

0 Street

STREETS

• •

M §TR$PP1 CHAR

Street 2

;IIY

n n

»D CITY1

CHAR

40"

0City

3E6IOH

• •

=TE610 CHAR

i 0 Region (State. Province. County)

:&UWTRY

• •

TAHPI CHAR

0 Country Key

WW COPE

n n

CPI

CHAR

0 City postal code

WNE NLFLBER

•

-O-

Iff TLHFLBR

;HAS>

©Telephone no dialling code^number

Figure 11.4 ABAP Dictionary Table Definition for Address Entity

For the purposes of this contrived example, we will minimize the overall number

of Fields used to represent a particular entity. For instance, the Table ZCA_PERSON

only contains a GUID-based key. fields to represent the first and last name of the

person, and two reference fields used to associate a person with an address. Sim-

ilarly, Table ZCA_ADORESS only contains a GUID-based key and some basic address

fields.

11.3.1 Creating a Persistent Class in the Class Builder

For the most part, you create persistent classes in the exact same way thatyou cre-

ate other global classes in the Class Builder. The only difference is in the class type

thatyou choose.

1. Select PERSISTENT CLASS as the CLASS TYPE (see Figure 11.5).

2. Click SAVE. The Class Builder takes you to the Class Editor screen where you can

begin editing the persistent class.

Figure 11.6 shows class ZCL_0S_A0DRESS after it is initially created. Here,

because you have not yet mapped the persistent fields for this class, the class

only contains implementations for the methods defined in interface

IF_OS_STATE.

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ABAP Object Services

IE-Create Class •

Class fCL.OS.AC-DRESS

Description Addiess Persistent Obiett

mstanfctton Protected a

Class Type/

0 Usual ABAP Class

O Exception Class

r Wift Message Class

|@Pers«4ient class )

0 Test Class (ASAP Unn>

0 Final

• Or.* Modeled

• 8_a*e] X

Figure 11.5 Creating Persistent Class ZCl_OS_ADDRESS

Local Types & implementation g Macros Persistence • Constructor 0 Class constructor Cla

Class interface ZCL_

DS_ADt>RESS

Implemented/Actrne

Properties interfaces Friends Attnoutes ^ISiSSH Events Types AJiases

0 Parameters 0} Exceptions |

-i H

IQ|<*r

3J&KJGI si oaka «

• F«er

[Method Level Vtsi |M

Description

HANDLE.EXCEPTION InstancPubll

Handles

Exception AJter

Reading State

[ 6ET InstancPubH

Obiect Services Prnrate. Copy Slate Obiect

INIT Instanc

PU.11 initializes Transient Part of Object State

SET Instant Publl

Obiect Services Prn-ate Replace State Objecl

INVALIDATE

Instanc

Publl invalidate Object State

Figure 11.6 Editing a Persistent Class

11.3.2 Defining Persistent Attributes with the Mapping Assistant

After you have created a persistent class, you can define its persistence represen-

tation:

1. Click on the PERSISTENCE button in the toolbar of the Class Editor screen (see

Figure 11.6). This takes you to the Mapping Assistant tool shown in Figure

11.7.

2. Initially, you are prompted to enter a table, view, or structure that will be used

as the basis for the persistence representation. For example, in Figure 11.7, we

288

Building Persistent Classes

11.3

are defining the persistence representation for class 2CL_OS_ADORESS using

Table 7CA_ADDRFSS (whose fields were shown earlier in Figure 11.4).

AAA

Type

9 ZCL_OS_ADORESf

IE-CU44 ZCL_OS_AOOR6SS Add Ubla/ttrucbjro

Table

Table's*

lure

2CA_A00ft£SS|

JB00QC 100

3 FALSE 3 C

IFTjteT

[Ofricnpton

Figure 11.7 Defining Persistence with the Mapping Assistant

3. After you have selected the relevant ABAP Dictionary object, begin editing the

persistent attributes of the class by double-clicking on any of the fields in the

TABLES/FIELDS display in the bottom panel of the Mapping Assistant screen.

4. This loads the field into the editing area in the middle of the screen (see Figure

11.8). Edit the attribute name (which doesn't have to be the same as the table/

structure field), description, visibility, accessibility, and assignment type.

<>2CC_OS_ADORESS"

BESEEM EB23

ramc

a os.6uio

PiwatB *

Read

0O OUID

Global* unique Meno tier

TdbteS/FlfcWS

| ZCA_ADORESS

> OUID

o STREET1

o STREETJ

o cny

o REGION

o COUNTRY

o POSTAL.COOE

o PHONE NUMBER

Jtf OS.OUID

AO.STREET

AO_STRSPPI

AO_CITY1

REOIO

LANOI

AO.PSTCOI

oiobaiv

unique

Wertrte'

Sore«

Street!

Citr

Region (Slate. Province. Count/)

Country Key

Crtr postal code

A0_TLNM8R Telephone no dialling cod8»numb«r

Figure 11.8 Mapping Persistent Class Attributes

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ABAP Object Services

5. In most cases, the default properties defined for a given field by the Mapping

Assistant will be correct. Of course, you may decide to restrict access to a par-

ticular field by customizing the visibility and accessibility properties. More-

over, you may need to modify the assignment type for certain fields. Table 11.2

provides a description of the assignment types that you can configure for a

given attribute.

Assignment Type Meaning

Business Key Derived by the Mapping Assistant for primary key fields of an

ABAP Dictionary table that has a semantic primary key. You can-

not change this particular assignment type.

GUID Derived by the Mapping Assistant for the primary key field of an

ABAP Dictionary table that has a GUID-based primary key. You

cannot change this particular assignment type.

Value Attribute Used to define nonkey attributes of a given ABAP Dictionary

object.

Class Identifier Used in conjunction with another table/structure field to uniquely

identify an object reference. The table/structure field must be of

type OS.GUIO.

Object Reference Used in conjunction with another table/structure field to uniquely

identify an object reference. The table/structure field must be of

type 0S_GUID.

Table 11.2 Persistent Attribute Assignment Types

6. Figure 11.9 shows the completed persistence representation for class

ZCL_OS_ADDRESS. After you have finished mapping the attributes, save your

changcs. and return to the Class Editor screen to activate the changcs to your

persistence class.

ClMtOttOit*

II UII»IHIW |ciM»K>r»n

I'**

lD»l<np»c«

**CL.OVC©R£SS . .

(OOS.GUID

M GUC ZCA>C©RE8S GtcO»»Uf>")ut Wc'ttWf

3TREET1

O AO.STRf tT

a STREET! ICA.AC0RE8S

T> STREET?

• AO.STRSPR1 B 8TREET2

JCA_AIORESS

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• «>.cnvi W CITY ZCAJCORESS C %

REWN

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ZCA/CORESS

R«gon auto.

Pro«n<».

C«jr«

COUNTRY

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CootriKn

t> POSTAL.COOC 0 o.r* STCCM

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PHOf£_NUMKR

• AO.T1.NW8R

a PVONE.WJMB

ZCAJCORESS

Ttkphyit

dm '.j tosc-romc.

Figure 11.9 Persistent Attribute Details for Class ZCL_OS_ADDRESS

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Building Persistent Classes

7. If this is the first time you have activated your changes, you are asked whether

or not you want to also activate the class actor (see Figure 11.10). Select the YF.S

button to generate the class actors for class ZCL_OS_ADDRESS (i.e., classes

ZCA_OS_ADDRESS and ZCB_OS_AODRESS).

[B-At State Persistent Classes B X

Shot*! the Class Aclor Also Be

Q Actuated?

Figure 11.10 Activating the Class Actor for a Persistent Class

Figure 11.11 shows the generated getter and setter methods for class

ZCL_OS_ADDRESS after it has been activated.

Class interface ZCL_OS_AOORESS implemented

Actwe

Properties interfaces Friend* Attributes ^'11 .f.f.lM Events Types Mases

0 Parameters 0} Exceptions i E

31®

^SIAFFIL A SASS L

• Filter

Method Level VTSI

Description

KrrfKjsr*TE>

HANOLE.EXCEPTION

Instarx

Publ

Handles

Exception

After Reading State

6ET

Instarx

Publ

Obiect Services Private Copy State Object

INIT

Instarx Publ

nitialnes Transient Pari of Object State

SET

Instarx Publ

Obiect Services Private Replace Slate Obiect

INVALIDATE

Instarx

Publ

rrvalidate Object State

S€T_STREET2

Instarx Publ

Sets Attribute STREET2

SET_STREET1

InstarxPubl •U

Sets Attribute STREET1

S€T_RE6I0N

Instarx

Publ >U

Sets Attribule REGION

S€T_P0STAL_C0[>E Instarx Publ

Sets Attribute POSTAL.CODE

S€T_PHONE_NUHBER

Instarx

Publ K)

Sets Attribute PHONE.NUMBER

SET_COUNTRY

Instarx

Publ

• 'J

Sets Altribule COUNTRY

SET.CITY

Instarx Publ •O

Sets Attribute env

&ET_STREET2

Instarx

Publ

Reads Attribute STREET2

6£T_STREET1

Instarx

Publ

Reads ABnbule STREETt

6£T_RE$I0N Instarx Publ

Reads AOibuie REOtON

&ET_P0STAL_C0DE

Instarx

Publ

Reads AGnbute POSTAL_CODE

6£T_PH0NE_NUHBER Instarx Publ

Reads Attribute PHONE.NUMBER

SET_C00NTRY

Instarx Publ

Reads AOibuie COUNTRY

&ET_CITY

Instarx Publ

Reads Attribute CITY

Figure 11.11 GET and SET Methods for Class ZCl_OS_ADDRESS

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11 | ABAP Object Services

11.3.3 Working with Object References

All of the attributes defined for class ZCL_0S_A0DRESS were based on simple, ele-

mentaiy table fields. However, there is a twist to class ZCL_0S_PERS0N. Here, as

you will recall, you want to provide the ability to associate an instance of class

ZCL_OS_ADDRESS with the ZCL_OS_PERSON instance. To achieve this kind of bind-

ing. you need to map two foreign key fields of type 0S_GUI0 to the

ZCL_OS_ADDRESS type.

1. Create a persistent class called ZCL_0S_PERS0N using the steps described in Sec-

tion 11.3.1, Creating a Persistent Class in the Class Builder.

2. Map the fields of Table

ZCA_PERSON

just as you did in Section 11.3.2, Defining

Persistent Attributes with the Mapping Assistant. However, be careful in the

way that you map the ADOR_CLASS and ADDR_REF database fields. These two

fields will be used together to uniquely define an object reference attribute

called AOORESS.

3. In Figure 11.12, notice that the CLASS IDENTIFIER assignment type has been used

to define the source field in Table ZCA_PERSON that will provide the GUID of the

persistent class pointed to by the object reference. This class GUID is quietly

assigned to every global class that is defined in the Class Builder. As you will

see, this low-level detail is transparent to users of the class agent API. Never-

theless, you still have to provide a mapping to this attribute for the object ref-

erence to be valid.

ADOfifSM

PuWlt

Chjfjo

Class identity

TaW«SffieldS

A TVP.

1 Des<npt»r>

fflZCA PERSON

ADOR.CLASS OS.GUO Globally

Unique ld«nM*r

0 AOCP_REF

OS.OUO Oiotoirr

unique idenMef

Figure 11.12 Setting the Class Identifier for an Object Reference

4. Finally, map the source field in Table ZCA_PERSON that will store the instance

GUID of an actual persistent object of type ZCL_OS_AOORESS. Here, notice that

the object reference assignment is qualified with the ZCL_0S_A0DRESS class cre-

ated earlier. This information is needed for the Class Builder to properly gen-

erate SET_ and GET_ methods for this object reference attribute. Figure 11.13

shows how this field was configured for class ZCL_0S_PERS0N.

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Working with Persistent Objects

11.4

TaM*i*iel<» |A |Type [Oescnpbon

[fflZCA^PtRSON

t ADOR.REF 08.0UID Oa»a* l«f««ei

WORESS

Global*? Unique

Mentrior

Pub* a CMftQta OetKKeferer.: •) ZCL_0$_M't>RESS|

Figure 11.13 Defining the Object Reference

Figure 11.14 shows the completed attribute details for the ADDRESS object ref-

erence. You can also see the signature of the generated SEI_ADDRESS and

GET_ADDRESS methods in Figure 11.15 and Figure 11.16. respectively.

CiMM«ant>i»

|L IA»M9T«<3 f«id ICiawiOFieW |Ta»e

[Oeurifoon I

~ 9 ZCL.OS.PEPSON

<g>

os.oue

0GUO ZCA_P€RSCN Global* Unique Id prat* f

NMC.FRST

O AO.NWEFR

(j WMEJR3T ZCA.PCRSCN

F ft* name

s> NAME.LAST

O AO.UWEIAS

3 UMft.LAST ZCA.PCRSON Law nam*

*>A©0«£SS

O ZCVjOQJCO

0AOC«_RtF

AOC«_CLAS$

ZCA.PCRSON

OlobaMr Unioua iderafar

Figure 11.14 Attribute Details for the ADDRESS Object Reference

Mettio«J parameter*

SETJWRESS

Mettioii i E» Eweptont | a

I.JM M

Paramo |T*«

Pa«» by value Optional iTyprjjMeriod [Associated Trpe Defauii |Oes(r*oon

b«*ESg i-nporting Type ftef To K*._0S_M<*£SS

MnMevnue

Type

Figure 11.15 Signature for Method SET_ADDRESS

Merioo parameters 6£i_A00R£SS

«=> K»T*>ds I QJ Excepbons |V 0 1

[Parameter [Type Pass By Vafc>e[Op«ionat Typing Memo<J

[Associated Tfl* [ce^njl value Descriptor!

ftSULr R«urninj Type Ref To

ZCLJ»_ADDRESS Aflnbute Value

Type

ZCLJ»_ADDRESS

Figure 11.16 Signature for Method GET_ADDRESS

11.4 Working with Persistent Objects

Now that we have defined a couple of persistent classes, let's look at ways to

interact with persistent objects of these classes using the generated API methods

of the associated class agents.

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ABAP Object Services

11.4.1 Creating New Persistent Objects

The code required to create a new persistent object is remarkably straightfor-

ward. Listing 11.1 shows how to create persistent objects of type ZCL_0S_A0DRESS

and ZCL_0S_PERS0N.

OATA: 1r_address_agent TYPE REF TO zca_os_address.

lr_address TYPE REF TO zc1_os_address.

1r_person_agent TYPE REF TO zca_os_person.

lr_person TYPE REF TO zcl_os_person.

TRY.

* First, create an address instance:

1r_address_agent - zca_os_address->agent.

CALL METHOO 1r_address_agent•>create_persistent

EXPORTING

i_city - 'Mos Eisley'

i_country - 'TAT'

i_phone_number - '999-555-5555'

i_postal_code - '99999-9999'

1.region - 'SKY'

i_streetl - '123 Millennium Falcon Way'

RECEIVING

result - lr_address.

* Next, create a person instance:

1r_person_agent - zca_os_person->agent.

CALL METHOD 1r_person_agent->create_persistent

EXPORTING

i_address - lr_address

i_name_first - 'Andersen'

i_name_last - 'Wood*

RECEIVING

result - lr_person.

* Must execute COMMIT WORK to persist the objects:

COMMIT WORK.

CATCH cx_os_object_existing.

ENDTRY.

Listing 11.1 Creating Persistent Objects

In both cases, a reference to the associated agent class had to be obtained via the

AGENT class attribute defined for the respective agent classes (i.e., classes

294