E-Wallet-App

Curl to Onboard User:

curl --location 'localhost:8083/user-onboarding/create/user'
--header 'Content-Type: application/json'
--data-raw '{ "name": "Som", "email": "somnath.try@gmail.com", "phoneNo": "123456677", "password": "12345", "userIdentifier": "AADHAAR", "userIdentifierValue": "56587452256", "dob": "14/02/2003", "address": "BTM Layout, Bangalore" }'

Curl to Make Transaction

curl --location --request POST 'localhost:8082/txn-service/initiate/transaction?amount=4&receiver=5635878963&purpose=Sending%20Mney%20to%20robin%204rs'
--header 'Authorization: Basic NTY5NzQ1NTI1MzoxMjM0NQ=='

Curl to see transaction history

curl --location 'localhost:8082/txn-service/transaction/history?mobile=5697455253'
--header 'mobile: 5697455253'
--header 'Authorization: Basic NTY5NzQ1NTI1MzoxMjM0NQ=='

Remember these Points

1. Kafka Should be up and running
2. Mysql Should be up and database should be created, take database name from application.properties file
3. Following topics needs to be created: user-details, txn-details, txn-update

💳 E-Wallet Application

A distributed Spring Boot microservices system enabling core digital wallet functionalities, including user onboarding, wallet creation, fund transfers, transaction tracking, and email notifications.

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📌 Features

• ✅ User registration with KYC verification
• 💼 Wallet creation & balance management
• 🔁 Money transfer between users
• 📜 Transaction history
• ✉️ Email notifications on onboarding

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⚙️ Architecture

[User Service] → Kafka → [Notification Service] 
               → Kafka → [Wallet Service]
[Transaction Service] → Kafka → [Wallet Service]
[Wallet Service] → Kafka → [Transaction Service]

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🧰 Tech Stack

• Java 17, Spring Boot 3.2.5
• MySQL, Apache Kafka
• Spring Security (Basic Auth), BCrypt
• Maven build
• Mailtrap for email testing

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🧩 Microservices Overview

1. 👤 User Service (Port: 8083)

• Endpoints:
  • POST /user-onboarding/create/user — Create user
  • GET /user-onboarding/get/user — Fetch user
• Highlights:
  • KYC via PAN/AADHAAR/VOTER_ID
  • Password encryption
  • Publishes to Kafka topic: user-details

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2. 💼 Wallet Service (Port: 8084)

• Creates wallet with ₹50 initial balance
• Transfers and updates balances
• Kafka:
  • Listen: user-details, txn-details
  • Publish: txn-update

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3. 🔄 Transaction Service (Port: 8082)

• Endpoints:
  • POST /txn-service/initiate/transaction
  • GET /txn-service/transaction/history
• Handles money transfers and logs transactions
• Basic Auth via phone:password
• Kafka:
  • Listen: txn-update

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4. 📩 Notification Service (Port: 8081)

• Sends welcome emails using Mailtrap
• Kafka:
  • Listen: user-details

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🛠️ Setup Instructions

✅ Prerequisites

• Java 17
• Apache Kafka (local)
• MySQL

🗃️ Databases

• walletuserdb (User)
• walletdb (Wallet)
• transactiondb (Transactions)

🧵 Kafka Topics

kafka-topics --create --topic user-details --bootstrap-server localhost:9092
kafka-topics --create --topic txn-details --bootstrap-server localhost:9092
kafka-topics --create --topic txn-update --bootstrap-server localhost:9092

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🚀 Running the App

# Common module
cd common
mvn install

# Services
cd ../UserService && mvn spring-boot:run
cd ../WalletService && mvn spring-boot:run
cd ../TxnService && mvn spring-boot:run
cd ../NotificationService && mvn spring-boot:run

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📲 API Usage

➕ Create User

curl --location 'localhost:8083/user-onboarding/create/user' --header 'Content-Type: application/json' --data '{
  "name": "John Doe",
  "email": "john@example.com",
  "phoneNo": "1234567890",
  "password": "secure123",
  "userIdentifier": "AADHAAR",
  "userIdentifierValue": "56587452256",
  "dob": "01/01/1990",
  "address": "City, Country"
}'

💸 Initiate Transaction

curl --location --request POST 'localhost:8082/txn-service/initiate/transaction?amount=100&receiver=9876543210&purpose=Payment' --header 'Authorization: Basic <base64(phone:password)>'

📜 Transaction History

curl 'localhost:8082/txn-service/transaction/history?mobile=1234567890' --header 'Authorization: Basic <base64(phone:password)>'

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🔒 Security

• Basic Auth with phone number
• Password hashing using BCrypt
• Role-based access (USER, ADMIN)

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📁 Config Files

Each service has its application.properties under:

• /UserService/src/main/resources/
• /WalletService/src/main/resources/
• /TxnService/src/main/resources/
• /NotificationService/src/main/resources/

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🧱 Key Classes & Components

Common Module

• CommonConstants
• UserIdentifier enum

User Service

• UserController, UserService, User

Wallet Service

• TransactionWorker, Wallet, OnboardedUserConsumer

Transaction Service

• TransactionController, TransactionService, Transaction

Notification Service

• EmailWorker, UserCreatedConsumer

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🧩 Database Schema

User Service: walletuserdb

CREATE TABLE user (
  id INT AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(255), email VARCHAR(255) UNIQUE,
  phone VARCHAR(255) UNIQUE, address TEXT,
  dob VARCHAR(20), password VARCHAR(255),
  user_identifier ENUM('PAN','AADHAAR','VOTER_ID'),
  user_identifier_value VARCHAR(255),
  role ENUM('USER','ADMIN'),
  user_status ENUM('ACTIVE','INACTIVE','BLOCKED'),
  created_on DATETIME, updated_on DATETIME
);

Wallet Service: walletdb

CREATE TABLE wallet (
  id INT AUTO_INCREMENT PRIMARY KEY,
  user_id VARCHAR(255), balance DOUBLE,
  phone_no VARCHAR(255) UNIQUE,
  user_identifier VARCHAR(50),
  user_identifier_value VARCHAR(255),
  created_on DATETIME, updated_on DATETIME
);

Transaction Service: transactiondb

CREATE TABLE transaction (
  id INT AUTO_INCREMENT PRIMARY KEY,
  txn_id VARCHAR(255), sender_id VARCHAR(255),
  receiver_id VARCHAR(255), amount DOUBLE,
  purpose VARCHAR(255),
  txn_status ENUM('INITIATED','FAILED','SUCCESS','PENDING'),
  txn_message TEXT,
  created_on DATETIME, updated_on DATETIME
);

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❗ Error Handling

• Global @ControllerAdvice handling
• DB & Kafka exception coverage
• Transaction status resolution via Kafka

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✅ Testing

mvn test

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📡 Monitoring

• Spring Actuator endpoints
• Kafka CLI tools
• DB consistency checks

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🧠 Troubleshooting

Issue	Solution
Kafka not reachable	Ensure Kafka runs on localhost:9092
DB connection errors	Check credentials in application.properties
Auth failures	Ensure correct Base64(phone:password)
Txn not processed	Check wallet balance & receiver user

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🌱 Future Enhancements

• Swagger API docs
• Circuit Breakers (Resilience4j)
• JWT Authentication
• Wallet balance check endpoint
• Admin dashboard
• Transaction reversal system

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📂 Repository Structure

.
├── common/
├── UserService/
├── WalletService/
├── TxnService/
├── NotificationService/
└── README.md

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📬 Contact

For any queries or contributions, feel free to open issues or raise pull requests.

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