Expense Tracker Workshop — Session 2

SQLite + Repository + Swagger

A follow-up workshop to Session 1. You take the request through the whole stack — Controller → Service → Repository → SQLite — make the data survive a restart, and document it with Swagger/OpenAPI (plus a bonus error handler). The core of the Controller doesn't change — that validates the layered architecture from Session 1.

Navazující workshop na Session 1. Provedeš request celým řezem Controller → Service → Repository → SQLite, data přežijí restart a zdokumentuješ je Swaggerem (+ bonusový error handling). Jádro ExpenseControlleru se nemění — to potvrzuje vrstvenou architekturu ze Session 1.

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How this repository works / Jak repozitář funguje

One Maven project. One folder. Seven steps. Otevřeš jeden projekt a postupně doplňuješ kód.

• start branch — the project in its starting state (working Session-1 API, data in a HashMap). The code is marked with // STEP N — … comments + // TODOs showing exactly where you write code. Začni tady: git switch start.
• main (= final branch) — the complete solution (the same single project, fully implemented). Each // STEP N — … comment sits above the code that step adds. Sem se podívej, když se zasekneš.

There are no step-NN folders anymore. Switch to start, open the repo root and follow STEPS.md from step 1 to step 7.

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How to run / Jak to spustit

Workshop participants / Účastníci: začni na větvi start (git switch start) a vyplňuj kód podle STEPS.md. Kroky níže fungují stejně na kterékoli větvi.

1. Open the project / Otevři projekt IntelliJ IDEA → File → Open → select the repository root folder (the one with pom.xml). Vyber kořenovou složku repozitáře (tu, kde je pom.xml) — ne podsložku. Počkej na stažení závislostí.

2. Run / Spusť

   ./mvnw spring-boot:run

   (Windows: mvnw.cmd spring-boot:run. Or just press ▶ on Application.kt in IntelliJ.)

3. Open Swagger UI / Otevři Swagger http://localhost:8080/swagger-ui/index.html — test the API in your browser.

4. Inspect the database / Podívej se do DB (from step 1 on / od kroku 1)

   sqlite3 expenses.db ".tables"
   sqlite3 expenses.db "SELECT * FROM expenses;"

Stuck? / Zasekl ses? The complete solution is on main (and the final branch):

git switch main      # complete solution / kompletní řešení (= final)
git switch start     # back to your work / zpět ke svému zadání

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Test the API / Otestuj API

Two ready-made ways to exercise the endpoints (app must be running):

• expense-tracker.http — open in IntelliJ and click the green ▶ next to each request (built-in HTTP Client; > {% ... %} blocks assert the status/body).
• smoke-test.sh — runs all the curl checks with ✅/❌:

  ./smoke-test.sh            # http://localhost:8080
  ./smoke-test.sh 8090       # custom port

⚠️ Use http://, not https://. The app speaks plain HTTP. Opening https://localhost:8080/... produces a blank page and a Tomcat "Invalid character found in method name" log line.

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Workshop steps / Kroky workshopu

Full guide with goals, tasks, hints and "done when…" checks: STEPS.md. Odkazy ke čtení k tématům / further-reading links: RESOURCES.md.

Request flow: Controller → Service → Repository → SQLite (see STEPS.md).

Step	Topic	What you build
1	SQLite setup & schema	expenses.db file on disk
2	Repository: INSERT & SELECT	ExpenseRepository with JdbcTemplate
3	Repository: DELETE & findById	Complete CRUD repository
4	Service → Repository	Data survives a restart!
5	OpenAPI / Swagger (+ live demo)	Production-ready Swagger docs
6 (bonus)	Error handling	Consistent JSON error responses (404/500)

Key moments / Klíčové momenty

Step	What happens
4	Data survives a restart! HashMap replaced by SQLite — Controller unchanged.
5	Swagger UI with descriptions + examples; live POST/GET demo through the whole stack.
6 (bonus)	Missing id → consistent 404 JSON instead of the default error page.

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Prerequisites / Předpoklady

• Completed Session 1 (expense-tracker-workshop-01) or Spring Boot basics
• IntelliJ IDEA Community + JDK 21
• sqlite3 CLI (brew install sqlite3 / apt install sqlite3)

Detailed install guide: SETUP.md.

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Tools / Nástroje

Tool	Usage
IntelliJ IDEA Community	All steps
JDK 21	Compilation and execution
sqlite3 CLI	Verifying data in the database
Swagger UI	Testing the API in the browser

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Related / Souvislosti

Session 1 — Kotlin & Spring Boot Basics https://github.com/UnityInFlow/expense-tracker-workshop-01

Next steps after the workshop:

• W01 Kotlin Idioms — idiomatic Kotlin for backend
• W02 Spring Boot Basics — advanced Spring Boot patterns