Practical Software Architecture with DDD

1. PRACTICAL SOFTWARE ARCHITECTURE
DDD, CQRS, EVENT SOURCING
@gboissinot
Grégory BOISSINOT
2021-03-04
Beyond buzzwords ?

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GRÉGORY BOISSINOT

3. STARTING
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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #1
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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #2
@gboissinot

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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #3
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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #4
@gboissinot

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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #5
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OBJECTIVE : BUILDING A USEFUL DOMAIN MODEL #6
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10. USE CASES
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Business intents

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LISTING USE CASES
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Storytelling

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LISTING USE CASES
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APPLYING DDD TACTICAL DESIGN PATTERNS
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Objects with rich behavior

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IDENTIFY AGGREGATES
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Driven by use cases
Respect for invariants
Aggregate as a
consistent unit

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AGGREGATES COMMUNICATION
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Driven by use cases
Aggregate as a
consistent unit

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APPLYING CLEAN ARCHITECTURE
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Get rid of Transaction Script

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USE CASE
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18. CQS
Command Query Separation
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COMMAND VS QUERY
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COMMAND VS QUERY
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Commands & queries are simple POJOs
MARKED INTERFACE
MARKED INTERFACE

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COMMAND VS QUERY
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COMMAND VS QUERY
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COMMAND VS QUERY
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THE ASSOCIATED COMMAND
THE AGGREGATE ROOT
THE REPOSITORY

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COMMAND VS QUERY
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THE ASSOCIATED QUERY
THE REPOSITORY
QUERY HANDLER METHOD

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USING A SHARED REPOSITORY
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SHARED REPOSITORY
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COMMAND BUS & QUERY BUS
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COMMAND BUS & QUERY BUS
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COMMAND BUS & REST CONTROLER
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30. CQRS
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Command Query Responsibility Segregation

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CQRS
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Reduce complexity with different models

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CQRS
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Single source
of truth
Replication

33. EVENT-DRIVEN
SYSTEMS
Event as the building block
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MODELLING WITH EVENTS
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EVENT IDENTIFICATION PROCESS
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DOMAIN EVENT
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EVENT
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A SMIPLE DTO
ALL INFORMATION

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EVENT
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EVENT DISPATCHER / EVENT HANDLER
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COMMUNICATION WITH APPLICATION EVENTS
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EVENT SOURCING
Events as the source of truth

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EVENT STORE
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Events as the source of truth
History of events.
The state by a replay of events.

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EVENT STREAMING
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EVENT SOURCING
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Replaying all events to get the final state

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MODEL EVENT-DRIVEN
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Aggregates apply events

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EVENT STORE - EVENT SOURCING
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Single source
of truth

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CQRS & EVENT SOURCING
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Single source
of truth

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CQRS
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MANAGING SYSTEMS
Choreography & Orchestration

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CHOREOGRAPHY
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No central coordinator. Simply know how to respond to events.
The participants are loosely coupled and don't have direct knowledge of each other.

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CHOREOGRAPHY
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ORCHESTRATION
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ORCHESTRATION - PROCESS MANAGER
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Knows the entire composition
Coordinates all parties
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ORCHESTRATION - PROCESS MANAGER
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