Who am I?

Damiano Petrungaro

Italy

source: www.vidiani.com

Tivoli (RM)

source: www.livitaly.com

Tivoli (RM)

source: www.romaest.org

Tivoli (RM)

source: www.tivolitouring.com

Tivoli (RM)

source: www.confinelive.it

Tivoli (RM)

source: www.greenparkmadama.it

Me everyday:

CQRS

It's a pattern that I first heard described by Greg Young.
At its heart is the notion that you can use a different model to update information than the model you use to read information.
 

command query responsibility segregation

https://martinfowler.com/bliki/CQRS.html

Command
vs
Query

Events

It's an immutable object used to represent something important that occurred in the domain.

Events

let's code

Domain model

It's a mutable object with an identity, it can be represented in different ways.

It's comparable to other entities by its ID.

Aggregate root

A DDD aggregate is a cluster of domain objects that can be treated as a single unit.
An example may be an order and its line-items, these will be separate objects, but it's useful to treat the order (together with its line items) as a single aggregate.

aka: write model

Value Object

It's an immutable object representing a value in a domain.
 

It's comparable to other value objects by its own values.

Domain Model

let's code

Command

It's a write operation!

Command

let's code

Extra: Repository

It's an abstraction layer to provide access to all the entities and the value objects related to an aggregate.

Extra: Repository

let's code

Read Model

A read model is a model specialized for reads, that is, queries.
It takes events produced by the domain and uses them to build and maintain a model that is suitable for answering the client's queries.
It can draw on events from different aggregates and even different types of aggregate.

Projection

Projection is a specialized representation of the state derivated from of our system

Read Model

&
Projector

let's code

Discussions & Questions

101

Let's do some homework