Hubble — Discord-Inspired Communication Platform

Class: 23KTPM2  |  Course: Software Development for Mobile Devices  |  Group: 02  |  Date: 27/01/2026

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Table of Contents

1. Overview
2. Tech Stack
3. Project Structure
4. Backend Setup & Run
5. Features
6. Assessment
7. Team Members

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1. Overview

Hubble is a mobile application inspired by Discord — the widely-used communication platform that supports real-time messaging, voice calls, and community management.

The goal of this project is to build a feature-complete clone of Discord's core functionalities on Android, while integrating AI Smart Reply technology to provide intelligent response suggestions and enhance the overall user experience.

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2. Tech Stack

Layer	Technology
Mobile	Java 21 (Android), XML Layouts
Backend	Java 21, Spring Boot 3.2
Database	PostgreSQL
Cache / OTP	Redis
Realtime	WebSocket (STOMP)
Authentication	JWT (Access Token + Refresh Token)
File Storage	AWS S3
Push Notification	Firebase Cloud Messaging (FCM)
Email	SMTP Gmail
AI Smart Reply	OpenAI API
Build Tool	Maven (Backend), Gradle (Android)
ORM	Spring Data JPA / Hibernate
Mapper	MapStruct

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3. Project Structure

hubble/
├── backend/                        # Spring Boot API Server
│   ├── src/main/java/com/hubble/
│   │   ├── HubbleApplication.java
│   │   ├── configuration/          # SecurityConfig, WebSocketConfig, JwtConfig
│   │   ├── controller/             # REST Controllers
│   │   ├── dto/
│   │   │   ├── request/            # Request bodies
│   │   │   └── response/           # Response bodies
│   │   ├── entity/                 # JPA Entities
│   │   ├── enums/                  # PresenceStatus, MessageType, ServerRole...
│   │   ├── exception/              # ErrorCode, AppException, GlobalExceptionHandler, ApiResponse
│   │   ├── mapper/                 # MapStruct interfaces
│   │   ├── repository/             # Spring Data JPA Repositories
│   │   ├── service/                # Business Logic
│   │   └── validator/              # Custom validation annotations
│   └── src/main/resources/
│       └── application.yml         # Application configuration
│
├── mobile/                         # Android App (Java + XML)
│   ├── app/src/main/
│   │   ├── java/com/hubble/        # Activities, Fragments, ViewModels, Adapters...
│   │   └── res/
│   │       ├── layout/             # XML layout files
│   │       ├── drawable/           # Icons, images
│   │       └── values/             # strings.xml, colors.xml, themes.xml
│   └── build.gradle
├── .gitignore
└── readme.md

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4. Backend Setup & Run

Prerequisites

• Java 21+
• Maven 3.9+
• PostgreSQL 15+
• Redis 7+

Configuration

Create the PostgreSQL database:

CREATE DATABASE hubble_db;

Edit the connection details in backend/src/main/resources/application.yml:

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/hubble_db
    username: <your_username>
    password: <your_password>

jwt:
  secret: <your_secret_key_minimum_32_chars>

Run

cd backend
mvn spring-boot:run

API server starts at: http://localhost:8080

Quick API Reference

Method	Endpoint	Description
POST	/api/auth/register	Register a new account
POST	/api/auth/login	Login
POST	/api/auth/refresh	Refresh access token
GET	/api/users/me	Get current user info
PUT	/api/users/{id}	Update user profile
GET	/api/users/{id}	Get user profile by ID

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5. Features

1. Authentication

• Register / Login with Email or Phone (similar to Discord ID)
• OTP verification (One-Time Password)
• Forgot password & account recovery

2. App Security

• App lock with PIN code (Passcode Lock)
• Multitasking screen protection (App Switcher Protection)
• Unknown device login alert (Device Alert)

3. User Profile

• Update Avatar (Crop / Rotate image)
• Edit Bio, Status, Nickname
• Personal QR Code (User Tag) for quick friend adding

4. Session Management

• View list of active logged-in devices
• Remote logout
• Automatic token renewal (Refresh Token)

5. Contacts & Friends

• Find friends by Username / Tag
• Manage friend requests (Send / Receive / Block)

6. Presence

• Display status: Online / Idle / DND / Offline
• Show "Last seen" timestamp
• Custom status message

7. DM List

• List of recent conversations
• Unread message count badge
• Pin important conversations

8. Text Chat

• Real-time send & receive (WebSocket)
• Standard Emoji / Icon support
• Sticker & Giphy integration (animated images)

9. Message Status

• Display: Sending / Sent / Delivered
• "Typing..." indicator
• Read receipts

10. Message Interaction

• Reply & Quote messages
• Forward & Copy content
• Unsend (retract) messages
• Edit sent messages
• Emoji Reactions

11. Media Sharing

• Send photos / videos from gallery (Multi-select)
• Capture photos / record videos directly (Camera)
• Media player & inline preview

12. Channel System

• Text Channels
• Voice Channels
• Channel Categories
• Private Channel permissions

13. Voice Messages

• Quick recording (Hold to record)
• Audio waveform visualization
• Proximity sensor (auto-switch earpiece / speaker)

14. File Attachments

• Send documents (PDF, Doc, Zip)
• Upload / Download progress bar
• Open files with third-party apps

15. Gallery

• Browse all Media / Links shared in a conversation
• Filter by content type (Images / Videos / Files)
• Download to device

16. Group / Server Management

• Create group, set name and avatar
• Manage members (Add / Invite / Kick)
• Role system: Owner, Admin, Member
• @Mention members / groups
• Invite via Link or QR Code

17. Search

• Search messages locally (on device) & globally (on server)
• Jump to original message location
• Highlight search keywords
• AI-powered search

18. Settings

• Theme: Dark Mode / Light Mode
• Push Notification settings
• App language (Vietnamese / English)

19. Notification System

• Push Notifications (FCM)
• In-app alerts
• Email notifications (for important events)

20. AI Smart Reply

• Context analysis of incoming messages
• 3 quick reply suggestions (Suggestion Chips)

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6. Assessment

Benefits

• High practicality: Engage with the architecture of a real-world complex application (Discord), tackling real-time communication and multimedia processing challenges.
• Intelligent experience: AI Smart Reply integration helps users respond quickly, making the app more convenient and modern.
• Deep technical skills: Hands-on experience with WebSocket, REST API, Cloud Storage, application security, and hardware interaction (Camera, Microphone, Proximity Sensor).

Challenges

• Data Consistency: Ensuring message consistency between Client–Server and across multiple devices under unstable network conditions.
• Performance: Handling latency when calling the AI service to analyze messages, and optimizing the loading of large message lists and media.
• Complex Business Logic: Domain-specific features such as role-based permissions (Roles), presence tracking, and conflict resolution when multiple users chat simultaneously.

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7. Team Members

No.	Full Name	Student ID
1	Hồ Văn Khải	23127015
2	Nguyễn Hoàng Đăng	23127166
3	Ngô Trần Quang Đạt	23127341
4	Nguyễn Gia Huy	23127378
5	Vũ Văn Vũ	23127543

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University of Science, VNU-HCM
Instructors: MSc. Trương Toán Thịnh, MSc. Hồ Tuấn Thanh
Semester 3 — Academic Year 2025–2026