Refactoring your Application to Data Oriented Programming The Amber Project José Paumard Java Developer Advocate Java Platform Group Antoine Dabot-Durand SCIAM Ana-Maria Mihalceanu Senior Developer Advocate Java Platform Group 

https://twitter.com/ammbra1508 https://mastodon.social/@ammbra1508 https://github.com/ammbra “DevOps Tools for Java Developers” guest author https://dev.java 

Antoine Sabot-Durand Java Champion IT Lead at SCIAM Former CDI spec lead Former MicroProfile Health & Fault Tolerance spec lead Follow me on Bluesky: @antoine.sabot-durand.net 

https://dev.java @josepaumard.bsky.social 

4/17/2025 Copyright © 2023, Oracle and/or its affiliates 5 https://dev.java/ 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 6 Tune in! Inside Java Newscast JEP Café Road To 21 series Inside.java Inside Java Podcast Sip of Java Cracking the Java coding interview 

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4/17/2025 Copyright © 2025, Oracle and/or its affiliates 9 https://bit.ly/devoxxfr25-dop-lab SSID : devoxxfr-hol Passwd : hola#4321 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 10 Structure of the Lab 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 11 Is it new? The Expression Problem: how to extend statically typed data abstractions, in representations and behavior, without having to recompile the existing code. User-defined Types and Procedural Data Structures as complementary approaches to Data Abstraction." Reynolds, John C. (1975). . New Directions in Algorithmic Languages (PDF). IFIP Working Group 2.1 on Algol. pp. 157–168. Foundations of Object-Oriented Languages (FOOL), Cook, William (1990), REX School/Workshop. Lecture Notes in Computer Science. Vol. 489. Noordwijkerhout. Data Oriented Programming 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 12 Polymorphism - Add new subtypes - No new operations Wadler’s Answer Pattern Matching - Add new operations - No new subtypes You cannot get both  If you are not the owner of the code: Phil Wadler 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 13 Because it has to do with long term maintenance of your applications When your business requirements evolve: 1) How can you add behavior to your Object Model? 2) Can you remove the behavior that becomes obsolete? Why is This Problem Interesting? 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 14 Structure of the Lab: Step 0 3 types of relationship: 1) Push 2) Pull 3) Pubsub A_Database B_Price-monitoring C_GUI D_Fligt-BP 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 15 Structure of the Lab: Step 1 3 types of relationship: 1) Push 2) Pull 3) Pubsub A_Database B_Price-monitoring C_GUI D_Fligt-BP 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 16 Fixing the Application / DB Relation DB FlightEntity (Hibernate) Business Module 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 17 Fixing the Application / DB Relation DB FlightEntity (Hibernate) Business Module Application of the Dependency Inversion Principle (SOLID) 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 18 Fixing the Application / DB Relation DB FlightEntity (Hibernate) Business Module 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 19 Refactoring to Data Oriented Programming - About creating sealed types, carrying only state Record FTW! - And adding behavior outside of these types Pattern Matching FTW! Structure of the Lab: Step 2 

4/17/2025 Copyright © 2025, Oracle and/or its affiliates 20 Final test: adding a new type, how does it go? Initial situation: you support simple flights Extension: you need to support multileg flights Structure of the Lab: Step 3