This document discusses mapping an existing database to new domain models when upgrading an e-commerce platform. It proposes using a wrapper layer to interface with legacy data models while building out new domain entity models aligned with Symfony best practices. A migration service would then handle converting data between the legacy and new target databases. Benefits include a cleaner object-oriented design, ability to introduce changes incrementally, and leveraging the mature and well-supported Symfony framework. Challenges include performance impacts and extensive testing needed for the wrapper layer.

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How To Map Domain Changes
On An Existing Database
OXID eSales AG
Philip Washington Sorst
Software Architect

2. © 2014 OXID eSales AG
An Example: The Article
Article
id
title
pic1
pic2
pic3

3. position
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An Example: The Product
id
1 of n
Product Picture
title path

4. Web Frontend REST
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Architecture (1)
Controller
Repositories
Presentation Layer
Data Layer

5. Web Frontend REST
© 2014 OXID eSales AG
Architecture (2)
Controller
Domain Services
Repositories
Presentation Layer
Business Logic Layer
Data Layer

6. ProductController
ProductServiceInterface CategoryServiceInterface
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The Business Logic Layer
ProductService CategoryService
DomainEntities DomainEntities
Data Layer

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An Example: The ProductInterface
interface ProductInterface
{
function getId();
function getTitle();
function setTitle($title);
function getPictures();
function setPictureAt($position, $path);
}

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An Example: The ProductWrapper
class ProductWrapper implements ProductInterface
{
protected $article;
function getId() { $this­>
article­>
getId(); }
function getPictures()
{
return array(
$this­>
article­>
getPic1(),
$this­>
article­>
getPic2(),
$this­>
article­>
getPic3());
}
...
}

9. Business Logic Layer
Data Layer
queries DomainEntityInterface
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The Data Layer
Repository
DAO
Service
Mapper
DatabaseEntityWrapper
DatabaseEntity
Row
queries
maps
returns
builds
queries

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/**
* @ORMTable()
* @ORMEntity()
*/
class Product implements ProductInterface
{
/**
* @ORMColumn(name="id", type="integer")
* @ORMId
* @ORMGeneratedValue(strategy="AUTO")
*/
private $id;
/** @ORMColumn(name="title", type="string", length=255) */
private $title;
/** @ORMOneToMany(targetEntity="Picture", mappedBy="article",
cascade={"ALL"}, indexBy="picture") */
private $pictures;

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Migration
MigrationService
LegacyRepository DoctrineRepository
LegacyDao
DomainEntityConverter
LegacyDB TargetDB

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Why we are using Symfony
> Open Source
> Focus on clean OO Development (DI, Events)
> Is more than a web framework
> Can be introduced step by step
> We don't need to reinvent the wheel, great bundles available
> We need to be easily extendable, so building bundles ourself
> Mature and well supported
> Superior Documentation

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Discussion: The Cons
> Performance might become an issue
– But our layered architecture allows us easily cache stuff
and build performance optimized services
> The wrapping needs much love (=time) to be fully backwards
compatible, testing
> Of course there are still some modelling limitations imposed

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Discussion: The Pros
> A redefined view on our own domain, built for the future
> We don't break things too early
> Design flaws can be identified and removed
> Things become exchangable, as soon as migration is possible
the wrapping will vanish
> Implicit migration for the database. Use the wrapper layer to
read, use the new domain to write

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Credits
> Icons:
– Shmidt Sergey (The Noun Project)

16. Thank you for your attention!
© 2014 OXID eSales AG
OXID eSales AG
Bertoldstraße 48
79098 Freiburg
GERMANY
www.oxid-esales.com
E-Mail: info@oxid-esales.com
Fon: +49 761 368 89 0