Loan Management System API

This is a comprehensive REST API built with Spring Boot to simulate the full lifecycle of a loan, from origination and payment tracking to closure and default. It's designed with a clean, layered architecture (Controller-Service-Repository) and follows best practices for API design and data handling.

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Features

• Loan Lifecycle Management: Create, track, and close loans.
• Payment Tracking: Record individual payments against a loan.
• Automated Business Rules:
  • EMI Calculation: Automatically calculates the Simple Interest, Total Repayable Amount, and Monthly EMI when a loan is created.
  • Overpayment Prevention: The API rejects any payment that would exceed the loan's remaining balance.
  • Auto-Closure: Automatically transitions a loan's status from ACTIVE to CLOSED when the final payment is made.
  • Auto-Default: A daily scheduled job checks for overdue payments. If a loan is past its grace period (10 days) and is underpaid, its status is automatically set to DEFAULTED.
• Pagination & Filtering: The GET /loans endpoint supports full pagination and sorting, as well as filtering by LoanStatus.
• Error Handling: Provides clear, JSON-based error messages for common issues (e.g., resource not found, invalid payments, validation errors).

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Tech Stack

• Framework: Spring Boot 3+
• Language: Java 17+
• Data: Spring Data JPA (Hibernate)
• API: Spring Web (REST Controllers)
• Database: MySQL
• Scheduling: Spring Task (@Scheduled)
• Utilities: Lombok
• Build: Apache Maven

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Getting Started

Prerequisites

• Java 17 or higher
• Apache Maven 3.6+
• A running MySQL server

1. Database Configuration

1. Create a new database in MySQL:

   CREATE DATABASE loan_db;

2. Update the src/main/resources/application.properties file with your MySQL username and password:

   # MySQL Database Connection
   spring.datasource.url=jdbc:mysql://localhost:3306/loan_db?createDatabaseIfNotExist=true
   spring.datasource.username=root
   spring.datasource.password=your_mysql_password
   spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
   
   # JPA Configuration
   spring.jpa.hibernate.ddl-auto=update
   spring.jpa.show-sql=true
   spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQLDialect

2. Run the Application

You can run the application using the Spring Boot Maven plugin:

mvn spring-boot:run