Quackstagram

A Java desktop application backed by MySQL, written for the Databases course project at the Department of Advanced Computing Sciences, Maastricht University, 2025-2026.

Quackstagram is a small social platform: accounts, image posts, likes, comments, follows and notifications. The course supplied a Swing interface that kept everything in text files. This project replaces that storage with a relational MySQL database, adds views, triggers and stored routines, and includes twenty standalone SQL query programs.

Layout

Path	Contents
src/main/java/quackstagram/model/	Database access layer, one store class per entity
src/main/java/quackstagram/ui/	Swing interface - course-supplied skeleton, database integration added
src/test/java/quackstagram/	The JUnit suite
sql/	Schema, seed data, views, triggers, and setup.sql to load them in the right order
queries/	Twenty standalone programs, Query1.java to Query20.java
img/	Icons, logos, and the profile and post images the seed data refers to
submission 1/	First-submission report and a manual database connection check
appendices/	Query timings before and after adding indexes on likes.post_id and follows.following_username
docs/	The course's original project README, kept for reference

Requirements

• JDK 21 - tested with Temurin 21.0.8 and OpenJDK 21.0.10
• MySQL 8 - tested against 8.0.46 and 8.4.8
• Maven 3.9 - for the build and the test suite
• MySQL Connector/J - Maven fetches it. For the manual javac build below, download it from https://dev.mysql.com/downloads/connector/j/ and put the JAR at lib/mysql-connector-j.jar.

Database setup

The code connects as user BCS1510 with password BCS1510, hard-coded in src/main/java/quackstagram/model/DBManager.java and in every queries/QueryN.java. Create that user, or change those constants:

CREATE USER 'BCS1510'@'localhost' IDENTIFIED BY 'BCS1510';
GRANT ALL PRIVILEGES ON quackstagram.* TO 'BCS1510'@'localhost';
FLUSH PRIVILEGES;

Then load the database. setup.sql drops and recreates the quackstagram database, and must be run from inside sql/:

cd sql
mysql -u BCS1510 -p < setup.sql

It finishes with Quackstagram database setup complete. and leaves 25 users, 45 posts, 30 comments, 103 likes, 52 follows, 35 notifications, 4 views and 3 triggers.

The order inside setup.sql matters. triggers.sql must load after populate_database.sql: on_like_insert increments posts.likes_count, so loading the triggers first counts every seeded like twice and invents notifications - and MySQL reports success throughout. setup.sql runs a pre-flight check first, so starting it from the wrong directory stops before anything is dropped.

Build

mvn package

That compiles the application and runs the test suite, which needs the test database (see Tests below). To build without a database:

mvn package -DskipTests

To build without Maven at all, from the repository root:

javac -d build/app $(find src/main -name "*.java")

That produces 24 class files. In a shell without find, use an argument file instead:

dir /s /b src\main\*.java > sources.txt
javac -d build\app @sources.txt

Run the application

From the repository root, so the image paths resolve:

java -cp build/app:lib/mysql-connector-j.jar quackstagram.ui.SignInUI

Windows uses ; rather than : between classpath entries. Sign in with any seeded account, for example checkpointmember / password123. If the database is unreachable the application says so and exits rather than opening empty screens.

Run a query program

From the repository root:

javac -d build/queries queries/*.java
java -cp build/queries:lib/mysql-connector-j.jar Query2

Query2 needs no input and prints one row per user. Queries that take a parameter read it from standard input.

Tests

The suite runs against a separate quackstagram_test database, so it never touches the one the application uses. Create it once:

cd sql
mysql -u BCS1510 -p < setup_test.sql

Then:

mvn test

Twenty-five tests over the data-access layer: credential checking, account creation, follow relationships, and the like/unlike cycle including the stored likes_count staying in step with the likes table. DBManager reads quackstagram.db.url, quackstagram.db.user and quackstagram.db.password as system properties and falls back to the application defaults, which is how the suite is pointed at the test database.

Passwords are stored as salted PBKDF2-HMAC-SHA256 hashes; the suite checks that no seeded account holds a password in the clear and that a crafted username cannot authenticate as a different account.

Known limitations

Verified, not hypothetical:

• Test coverage is limited to the data-access layer. The Swing interface has no automated tests. The application refuses to start when the database is unreachable, but a failure during a session is logged to the console rather than shown to the user. submission 1/DBConnectionTest.java is a manual connection check kept for the record rather than a test: it prints what it finds and always exits 0, including when the users table is missing entirely.
• Query1 and Query20 run identical SQL. The coursework brief specified both as follower-count thresholds over the user_follower_stats view, so the duplication comes from the specification rather than from the code.

Provenance and licence

Part of this repository was supplied by the course rather than written by its authors - see NOTICE for which files. docs/original-course-README.md is the course's original project README, kept for reference; its account of data/credentials.txt and text-file storage describes the starting point, not this code.

The authors' own work is MIT licensed. See LICENSE.