Refactoring Toward Deeper Insight DDD Cologne Bonn Meetup / Jul 2, - - PowerPoint PPT Presentation

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Refactoring Toward Deeper Insight DDD Cologne Bonn Meetup / Jul 2, - - PowerPoint PPT Presentation

Jan 31, 2024 560 likes •1.18k views

Refactoring Toward Deeper Insight DDD Cologne Bonn Meetup / Jul 2, 2020 Christoph Baudson / @sustainablepace Christoph Baudson Software dev at REWE Digital since 08/2015 Organizer of the DDD Meetup Cologne @sustainablepace /

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Refactoring Toward Deeper Insight

DDD Cologne Bonn Meetup / Jul 2, 2020 Christoph Baudson / @sustainablepace

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Christoph Baudson

  • Software dev at REWE Digital since 08/2015
  • Organizer of the DDD Meetup Cologne
  • @sustainablepace / sustainablepace.net
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  • 1. Some theory
  • 2. Example
  • a. The domain
  • b. Let’s code!
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Domain experts Developers

Domain Model

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Misconception!

Modeling in Domain-Driven Design is a waterfall-like big design up-front, and therefore not agile

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Insights

  • No one gets the model correct the first time.
  • The model changes over time.
  • The model is never done.
  • The model needs to be refactored

throughout the development lifecycle.

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Micro-Refactorings

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Refactoring to patterns Micro-Refactorings

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Refactoring to deeper insight Refactoring to patterns Micro-Refactorings

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Domain experts Developers

Domain Model

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Misconception!

When doing µServices, doing a rewrite is easy

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Insights

  • The domain knowledge is lost after rewriting
  • All dialogue has to happen all over again.
  • It’s hard to guarantee it will work as before.
  • Doing the same thing twice and expecting

improvements is foolish.

  • The domain model is an asset!
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  • 1. Some theory
  • 2. Example
  • a. The domain
  • b. Let’s code!
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Deposit Categories

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Deposit Map

Updates after 2 weeks

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  • 1. Some theory
  • 2. Example
  • a. The domain
  • b. Let’s code!
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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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Refactoring to patterns Micro-Refactorings

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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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Creates the deposit map, based on the last update.

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Nullable?

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Nullable? What does min date mean?

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Nullable? What does min date mean? Another from date?

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Nullable? What does min date mean?

  • > Nullable input is leaking in from infrastructure

Another from date?

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Why should a service assemble parts of the Map? I need to think about this...

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Why should a service assemble parts of the Map? I need to think about this...

  • > The deposit map should be build in the domain
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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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The boundaries are not enforced. ….and this obscures the business logic. Is there any?

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Is there anything to be learned from the model?

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YES! We forgot about another use case ;)

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  • > Let’s add these concepts of the model to the code...
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  • > Let’s add these concepts of the model to the code...

Input is no longer nullable!

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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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  • > Null check is moved outwards to infrastructure
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  • > Null check is moved outwards to infrastructure

There is a service for each use case now...

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Misconception!

Don’t repeat yourself!

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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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  • > Let’s move the deposit map creation to the domain
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Two different public factory methods

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dataDrop is encapsulated in model Naming could be improved...

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Data conversion happens in the background

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INFRASTRUCTURE APPLICATION SERVICES DOMAIN

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Apparently, there is no business logic...

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Apparently, there is no business logic... Added a new repository method to eliminate nullability...

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There is one business rule that was obscured before...

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There is one business rule that was obscured before... OK! We send a full map if the categories have been updated :)

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Parameters are not

  • null. Min Date has

been eliminated.

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Refactoring to deeper insight Refactoring to patterns Micro-Refactorings

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  • 1. Some theory
  • 2. Example
  • a. The domain
  • b. Let’s code!
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Afterthoughts

  • It might not be the best example
  • We were merely reminded about domain

concepts we didn’t translate to code

  • It was not a breakthrough
  • But the code is now aligned again with

the domain model! Hexagon ftw!

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Recommendations

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Let’s learn more about tactical design. Contact me! Questions?

Christoph Baudson / @sustainablepace