---
title: "How to effectively compose your business logic"
url: https://daily.dev/posts/how-to-effectively-compose-your-business-logic-b3ywmasiu
source_url: https://event-driven.io/en/how_to_effectively_compose_your_business_logic
type: article
source: "Event-Driven by Oskar Dudycz"
published: 2026-06-17T11:26:18.122Z
updated: 2026-06-17T11:32:40.158Z
tags: ["general-programming", "java", "architecture", "functional-programming", "domain-driven-design"]
reading_time: 12
upvotes: 0
comments: 0
language: en
---

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# How to effectively compose your business logic

**[Event-Driven by Oskar Dudycz](https://daily.dev/sources/event-driven-io)** · 12 min read · 0 upvotes · 0 comments

## Summary

A practical walkthrough of modeling business logic using Java 17 features — records, sealed interfaces, and pattern matching — to implement a shopping cart as an explicit state machine. The post introduces the Decider pattern (coined by Jérémie Chassaing), showing how to compose pure functions for command handling and state evolution in an Event Sourcing context. The approach yields self-documenting, immutable, strongly-typed code with a single entry point for business logic, making it easy to test and extend.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://event-driven.io/en/how_to_effectively_compose_your_business_logic>

---

Tags: [#general-programming](https://daily.dev/tags/general-programming), [#java](https://daily.dev/tags/java), [#architecture](https://daily.dev/tags/architecture), [#functional-programming](https://daily.dev/tags/functional-programming), [#domain-driven-design](https://daily.dev/tags/domain-driven-design)

[View this post on daily.dev](https://daily.dev/posts/how-to-effectively-compose-your-business-logic-b3ywmasiu)