TaskMgr - Java Task Manager

Author: Félix Vandenbroucke · 2026

Task management application built in pure Java, with no framework or external dependency. Two modes: interactive terminal and dark mode web interface with a REST API. JSON persistence with atomic writes, 217 tests, GitHub Actions CI.

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Features

• Create, edit, delete tasks with title, description, due date, status and priority
• Priorities LOW / MEDIUM / HIGH with colored pills in the UI
• Statuses TODO / DOING / DONE with list view and Kanban board (drag & drop between columns)
• Colored due dates: orange if ≤ 3 days away, red if overdue
• Filters by status, live search, global progress bar in sidebar
• CSV export in one click
• Keyboard shortcuts: n new task · Ctrl+Enter save · Escape close
• Full console mode with interactive menus

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Stack

Layer	Technology
Backend	Java 21, com.sun.net.httpserver (JDK built-in)
Frontend	HTML / CSS / vanilla JS, zero framework
Persistence	Hand-rolled JSON with atomic writes
Tests	Hand-rolled framework, zero external dependency
CI	GitHub Actions

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Project structure

taskmanager/
├── src/
│   ├── Main.java              entry point - console and web modes
│   ├── Task.java              data model, JSON serialization, CSV export
│   ├── TaskManager.java       CRUD, persistence, statistics
│   ├── ConsoleUI.java         terminal interface
│   └── ApiServer.java         multi-threaded REST HTTP server
├── tests/
│   ├── TaskManagerTest.java   129 assertions - business logic
│   └── ApiServerTest.java      88 assertions - HTTP integration
├── web/
│   ├── index.html             HTML structure
│   ├── style.css              styles (dark mode, kanban, animations)
│   └── app.js                 frontend logic (API calls, render, drag & drop)
├── .github/workflows/ci.yml   GitHub Actions CI pipeline
├── Dockerfile                 multi-stage container build
├── Makefile                   task automation (build, test, run)
├── data/                      folder mapped for persistence
│   └── tasks.json             auto-saved data
└── README.md

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Prerequisites

Java 17 or higher (uses switch expressions).

java -version
javac -version

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Quick start

# Build
make build

# Console mode
make run

# Web mode → http://localhost:8080
make web

# Custom port
make web PORT=3000

Without Make:

mkdir -p out
javac -d out src/Task.java src/TaskManager.java src/ConsoleUI.java src/ApiServer.java src/Main.java
java -cp out taskmanager.Main --web

Docker

docker build -t taskmanager .

# Run the container and map the data directory so your tasks are saved permanently
# On Mac/Linux:
docker run -p 8080:8080 -v "$(pwd)/data:/app/data" taskmanager

# On Windows (PowerShell):
docker run -p 8080:8080 -v "${PWD}/data:/app/data" taskmanager

JAR

make jar
java -jar TaskManager.jar --web

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REST API

Method	Endpoint	Description
GET	/api/tasks	List all tasks
GET	/api/tasks?status=TODO	Filter by status (TODO/DOING/DONE)
POST	/api/tasks	Create a task
PUT	/api/tasks/{id}	Update a task (partial fields supported)
DELETE	/api/tasks/{id}	Delete a task
GET	/api/stats	Stats by status
GET	/api/export	Export all tasks as CSV
GET	/	Serves the frontend

JSON body for POST / PUT:

{
  "title": "Task name",
  "description": "Optional details",
  "dueDate": "2026-06-15",
  "status": "TODO",
  "priority": "HIGH"
}

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Engineering highlights

• Multi-threaded HTTP server: FixedThreadPool with daemon threads handles REST requests in parallel without blocking the JVM, enabling clean server shutdown and reliable test teardown.
• Atomic persistence: write-to-temp strategy - data is written to a .tmp file then ATOMIC_MOVEd to the final file, preventing any corruption on crash.
• Lightweight Docker image: multi-stage build using eclipse-temurin:21-jdk-alpine to compile, then eclipse-temurin:21-jre-alpine for the final image - only the JRE and the JAR ship.
• CI with timeouts: GitHub Actions pipeline with 5-minute timeouts per step and separate unit/integration test jobs.

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Tests

217 assertions, zero external dependency.

# Run all
make test

# Unit tests only (Task, TaskManager)
make test-unit

# Integration tests only (HTTP, REST API)
make test-api

Without Make:

javac -cp out -d out tests/TaskManagerTest.java tests/ApiServerTest.java
java -cp out taskmanager.TaskManagerTest
java -cp out taskmanager.ApiServerTest

Integration tests spin up a real HTTP server on a random free port and fire real HTTP requests - no mocks. Returns exit code 0 if all pass, 1 otherwise (CI-compatible).

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tasks.json format

Updated automatically after every add, edit or delete. Atomic write: data goes to a .tmp file first, then moves to the final file - no data loss on crash.

[
  {"id":1,"title":"Set up the environment","description":"Install JDK 21","dueDate":"2025-02-28","status":"DONE","priority":"HIGH"},
  {"id":2,"title":"Write unit tests","description":"Cover Task and TaskManager","dueDate":"2025-03-10","status":"DOING","priority":"MEDIUM"},
  {"id":3,"title":"Write documentation","description":"README and Javadoc","dueDate":"2025-03-15","status":"TODO","priority":"LOW"}
]

Fields: id, title, description, dueDate (ISO format: YYYY-MM-DD), status, priority. Files without a priority field load with MEDIUM as default (backward compatible).