Domain Driven DesignGérôme Egron !Nicolas Jozwiak

Programmeur et agiliste!!@njozwiak

Programmeur et agiliste!!@njozwiak

Xebia consultant since 2012.!!

@geromeegron

SOMMAIRE• Domain Driven Design!!• Les principaux concepts!!• Architecture hexagonale!!• Hands On!

Domain Driven Design

REFERENCES

DOMAIN

• Core business of the company!!• Represents a sphere of knowledge!!• Create best software by concentrating on the

problems related to the domain!

DOMAIN

• Not focus on technologies!!• Ubiquitous language !! structured language around the domain model and used by all team members 

MODEL DRIVEN DESIGN

• Represents the domain model in terms of software!!• Code modification means changing model!!• Model is adapted to a usage, a context

PATTERNS

ENTITIES

• entity = identity + state!!• long lifecycle!• has to have an operational way of applying identity!• Identity has to be guaranted unique within the system

ENTITIES

• The object state is the sum of its data values which define it at a precise moment in time!

!• Different stable state which occurs with transformations!!• Mutable and immutable attributes!

VALUE OBJECTS

• No conceptual identity!!• Immutable!!• Focus of their domain!!• Reflect constraints!

VALUE OBJECTS

• Help to define the state of other entities objects!!• Construction has to be meaningful and well formed

VALUE OBJECTS

void addCustomer(String, String)

void addCustomer(Name, PhoneNumber)

• Make implicit concepts explicit

AGGREGATES

• Treats domain objects as a single unit!!• Operations have to interfer with root!!• Ensure integrity of the whole!

SERVICES

• When a significant process or transformation in the domain is not a responsibility of an entity or value object!!• Define an interface in terms of language of the model!!• Have to be stateless!

SERVICE TYPES

• Domain service!!• Infrastructure service!!• Application service

REPOSITORIES

• Mediator between data access and domain layer!!• Root entity

BOUNDED CONTEXT

• Model has a limit!!• Communication with others domains!!• anticorruption layer!• conformist!• shared kernel!• customer/supplier relationship!• separate ways!• open host

ARCHITECTURE HEXAGONALE

Port and Adapter

Alistair Cockburn

Port / Adapter

Domain

X

Port / Adapter

Interface

Repository / Mock

Port / Adapter

Domain

Rest Adapter

Rest Port

Queue Adapter

Queue Port

Port / Adapter

https://github.com/xebia-france/workshop-ddd