Java Todo App

Java Todo App is a small full-stack todo list, but the point of it was the backend. I wanted a clean, honest example of the three-boxes shape every web app really is — browser, backend, database — with each layer doing exactly one job and nothing leaking across the boundaries.

The core#

The backend is Java on Quarkus. It exposes a REST API under /api/todos with the verbs mapped to what they actually mean: GET to list, POST to create, PUT to toggle a todo complete, PATCH to edit its text, and DELETE to remove it. Persistence is PostgreSQL 16 through Hibernate ORM with Panache, using the Active Record style so the todo entity carries its own query methods and the resource layer stays thin — it takes the request, calls the entity, and returns a result, without SQL or persistence details bleeding into the HTTP layer.

Architecture#

The browser never touches the database; it always goes through the backend, and the backend is the only thing that talks to Postgres. The frontend is deliberately plain — HTML, CSS and vanilla JavaScript — and it's served from the same origin as the API, which sidesteps CORS entirely and keeps the whole thing one deployable unit. The database runs in Docker Compose, so docker compose up plus ./mvnw quarkus:dev is the entire setup, and Quarkus's live-reload dev mode means backend changes show up without a manual restart.

Why I built it#

This was a learning project with a teaching goal: the repo ships a beginner-friendly README that traces a single todo from click to saved row and back, so the codebase doubles as an explanation. Keeping the design clean — clear layers, standard REST semantics, a real relational database rather than an in-memory shortcut — was the whole exercise. It's the small, focused version of the same backend discipline I carry into larger Quarkus projects.