Practice Project Modules: Backend Functionalities and Integrations

To establish @pepcus tasks

This repository includes various modules for practicing and demonstrating backend development using Java Spring Boot. It covers real-world backend tasks such as WhatsApp API integration with Meta, complex SQL joins, and bulk data import from Excel files or CSV files using Postman.

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🚀 Modules Included:

1. WhatsApp Messaging (Meta API via Webhooks)

• Description: Send and receive automated WhatsApp messages using Meta’s WhatsApp Cloud API, with webhook routing via Hookdeck and tunneling via Loophole.
• Tech Used:
  • Backend: Java 17, Spring Boot
  • WhatsApp API: Meta for Developers
  • Webhook Routing: Hookdeck
  • Tunneling: Loophole
• Features:
  • Send text messages to WhatsApp users
  • Verify webhook setup
  • Environment-based configuration for secure tokens

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2. WhatsApp Integration Setup

• Description: End-to-end setup and integration of Meta’s WhatsApp Cloud API using Spring Boot.
• Tech Used:
  • Spring Boot for REST API and webhook listener
  • Hookdeck for webhook monitoring
  • Loophole for exposing local server
• Setup Instructions:
  • Create a Meta Developer account and WhatsApp App
  • Receive and log incoming messages via webhook
  • Generate access token and configure webhook callback URL
  • Use Hookdeck to forward webhook traffic to localhost
  • Use Loophole to tunnel local Spring Boot server to a public endpoint
  • Add verify.token, access.token, and phone.number.id in application.properties

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3. Store Data in Local JSON File

Description: Implements functionality to save submitted form or API request data into a local JSON file. This provides a backup or logging mechanism to track all incoming data, useful for auditing or recovery.

Tech Used:

• Java Spring Boot
• Jackson Library (for JSON serialization)
• File I/O (Java NIO or standard I/O)

Features:

• Automatic JSON file creation and update on each data submission
• Appends new entries to maintain a full log
• Useful for offline access, debugging, or data recovery scenarios

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4. Join Three Tables in SQL

• Description: Demonstrates SQL JOIN queries using Spring Boot and MySQL. Example uses Users, Co-ordinators, and TimeTable tables to retrieve combined relational data.
• Tech Used:
  • Java Spring Boot
  • MySQL
  • Spring Data JPA or native SQL queries
• Example Use Case:
  • Join co-ordinators, user, and timetable tables to fetch user info with their order and product details
• Features:
  • REST API endpoint to fetch joined data
  • Clean model and repository structure
  • On registering, all submitted values are also stored in a local JSON file for backup/logging purposes.

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5. Bulk Upload from Excel to MySQL

• Description: Upload an Excel (.xlsx) file via Postman and insert the data into MySQL in bulk.
• Tech Used:
  • Java Spring Boot
  • Apache POI (Excel file parsing)
  • MySQL
  • Postman for API testing
• Features:
  • Upload Excel file via multipart/form-data endpoint
  • Parse and validate rows using Apache POI
  • Batch insert validated records into MySQL
  • API returns success/failure response for each row

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6. Bulk Upload from CSV to MySQL with OpenAPI Documentation

• Description: Upload a CSV (.csv) file via a REST API and insert the data into MySQL in bulk.

• Tech Used:

  • Java Spring Boot
  • OpenCSV (CSV file parsing)
  • MySQL
  • Postman for API testing

• Features:

  • Upload CSV file via multipart/form-data endpoint
  • Parse and validate CSV rows using OpenCSV
  • Perform batch insertion of valid records into MySQL
  • API response showing success/failure for each record

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7. Convert Database Records to PDF Report with REST API

• Description: Generate a downloadable PDF file containing data fetched from a MySQL database using a Spring Boot REST API.

• Tech Used:

  • Java Spring Boot
  • iText PDF or OpenPDF (PDF generation)
  • MySQL
  • Postman for API testing

• Features:

  • Fetch records from MySQL using JPA/Hibernate
  • Format data into a structured PDF (e.g., tables, headings)
  • Downloadable via a /export/pdf GET endpoint
  • Customizable report layout (title, date, pagination, etc.)
  • Error handling for empty data or generation failures

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🧪 How to Use

Prerequisites

• Java 17+
• Maven
• MySQL database setup
• Postman for testing APIs
• Hookdeck & Loophole accounts (for WhatsApp webhook)

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