Loan Management API

A Spring Boot based REST API for managing loan applications, payments, and documents.
This project simulates a simplified Loan Management System where users can apply for loans, track their loan status, pay EMIs, and upload documents.

The API is secured using JWT Authentication and documented with Swagger (OpenAPI).

---

Features

Authentication

• User registration
• Login with JWT token
• Role-based access (USER / ADMIN)

Loan Management

• Apply for loan
• View personal loans
• View loan details
• Admin can view all loans

EMI Management

• Automatic EMI generation
• Track EMI status

Payment Processing

• Pay EMI
• Payment tracking
• View all EMI of loans

Document Management

• Upload loan documents
• Associate documents with loan

API Documentation

• Interactive API testing via Swagger Loan Management

Interactive API testing via Swagger

Tech Stack

Backend Framework

• Spring Boot

Security

• Spring Security
• JSON Web Token (JWT)

Database

• PostgreSQL
• Hibernate
• Spring Data JPA

API Documentation

• Swagger UI
• OpenAPI

Utilities

• Lombok
• Apache Maven

---

System Architecture

Client (Frontend / Postman)
        │
        ▼
REST Controllers
        │
        ▼
Service Layer
        │
        ▼
Repository Layer
        │
        ▼
Database (PostgreSQL)

Layers

Controller Layer

• Handles HTTP requests and responses.

Service Layer

• Contains business logic.

Repository Layer

• Handles database operations using JPA.

DTO Layer

• Transfers request and response data.

Security Layer

• Handles authentication and authorization using JWT.

Project Structure

Loan-API
|
├──Configuration
|     ApiPrefixConfig
|     FilterConfig
|     SwaggerConfig
│
├── controller
│     AdminController
│     AuthController
│     DocumentController
│     EmailVerificationController
|     EMIController
|     Hello
|     LoanController
|     LoanPaymentController
|     PaymentController
|     UserController
│
├── dto
│     request models
│     response models
│
├── filter
│     JwtAuthenticationFilter
│
├──jwttoken
|     JwtUtils
│
├── entity/modul
│     User
│     Loan
│     EMISchedule
│     LoanPayment
│     Document
|     Email
│
├── repository
│     LoanRepository
│     UserRepository
|     DocumentRepository
|     EmailRepository
|     EMIRepository
|     LoanPaymentRepository
|
├── responseapi
|     APIResponse
│
├── service
|     AdminService
|     AuthService
│     DocumentService
|     EmailService
|     EMIService
|     UserDetailServiceImp
|     UserService
│     LoanService
│     LoanEmiPaymentService
|
├── status
|     DocumentStatus
|     DocumentType
|     EMIStatus
|     LoanStatus
|     PaymentMode
│
├── uitls
|     Common
|     EmailUtil
|     RazorPaymentVerificationUtil

Authentication Flow

User Login
   │
   ▼
AuthController
   │
   ▼
JWT Token Generated
   │
   ▼
Client stores token
   │
   ▼
Client sends token in request header

Authorization: Bearer <token>

API Modules

Authentication APIs

• POST /api/v1/auth/register
• POST /api/v1/auth/login

Loan APIs

• POST /api/v1/loans/{loan_id}/document
• POST /api/v1/loans/apply
• GET /api/v1/loans/my
• GET /api/v1/loans/{id}
• GET /api/v1/loans/get/all/loan

Document APIs

• POST /api/v1//loan/document/{documentId}/status
• GET /api/v1//loan/document/{loanId}/download/{documentId}
• GET /api/v1//loan/document/all

Payment APIs

• POST /api/v1//loan/emi/{loanId}/pay/{emiId}
• GET /api/v1//loan/emi/{id}/emi-schedule/get/all

Admin APIs

• GET /api/v1//admin/all/users

Email APIs

• GET /api/v1/email/verify

Payment APIs

• GET /api/v1/loan/emi/transaction/{loanId}

User APIs

• POST /api/v1/user/update
• GET /api/v1/user/get/user

Hello Test APIs

• GET /api/v1/hello/hello

Example Loan Apply Request

• POST /api/v1/loans/apply

Request

{
  "amount": 50000,
  "interestRate": 10.5,
  "tenure": 12
}

Response

{
  "code": 0,
  "message": "string",
  "data": {
    "loan_id": 3,
    "amount": 50000,
    "interestRate": 12.5,
    "tenureMonths": 12,
    "status": "DOCUMENT_PENDING",
    "createdAt": "2026-03-16T12:43:56.614Z"
  }
}

Running the Project

1 Clone the Repository git clone https://github.com/pankajtariyal/Loan-API.git

2 Navigate to the Project cd Loan-API

3 Configure Database Update application.properties

spring.datasource.url=jdbc:postgresql://localhost:5432/loan_db
spring.datasource.username=postgres
spring.datasource.password=yourpassword
spring.jpa.hibernate.ddl-auto=update

4 Build the Project mvn clean install

5 Run the Application mvn spring-boot:run

Server will start at http://localhost:8080/122

API Documentation

Swagger UI: http://localhost:8080/swagger-ui/index.html

OpenAPI specification: http://localhost:8080/v3/api-docs

Swagger allows:

• Viewing all APIs
• Testing endpoints
• Sending authenticated requests

Security

The API uses JWT Authentication. Include the token in requests: Authorization: Bearer <JWT_TOKEN>

Swagger UI also provides an Authorize button for authenticated requests.

Future Improvements

• Loan approval workflow
• Credit score integration
• Notification service
• Payment gateway webhooks
• API rate limiting
• Docker deployment
• CI/CD pipeline

Author

Abhishek Tadiwal

GitHub

https://github.com/pankajtariyal