CustomerManagerService – Local Server Branch (main)

CustomerManagerService is a Spring Boot-based RESTful API for managing customer records, designed with reliability, modularity, and testability in mind. This branch implements file-based persistence, enabling easy local testing without external cloud dependencies.

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🔍 Overview

This RESTful service allows creation and retrieval of customer records. Key features include:

• Validation of request data
• Manual sorted insertion (without .sort())
• File-based persistence to retain data across server restarts
• Modular, testable architecture (controller-service-persistence pattern)

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💡 Architecture

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🔧 Components

• CustomerController – handles API endpoints
• CustomerService – business logic and validation
• CustomerPersistence – handles file-based read/write
• GlobalExceptionHandler – centralized error handling
• CustomerApiSimulator – generates POST/GET requests for load testing

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🛠 Key Features

• ✅ RESTful API with POST and GET endpoints
• ✅ Manual sorted insertion by lastName, then firstName
• ✅ Input validation using @Valid and custom logic
• ✅ Global exception handling for both schema and business rule violations
• ✅ File-based persistence (via Jackson) with option to extend to cloud (e.g., GCS, DynamoDB)
• ✅ JUnit + MockMvc test coverage
• ✅ API simulator to test performance under concurrency

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Phased Delivery Approach

⬆️ Phase 1: Core Functionality (MVP)

• Define model (Customer)
• Implement /customers POST and GET
• Manual insertion without .sort()
• File-based persistence with Jackson

⬆️ Phase 2: Enhancements

• Adding Unit Test and Integration Test
• Structured error handling
• Simulator
• Modular folder structure
• Cloud migration implemented separately (cloud-integration branch)

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How to Run

🛠 Prerequisites

• Java 17+
• Maven 3.8+
• IntelliJ or any Java IDE

🏃 Running the App

Option 1: From IntelliJ

• Open CustomerManagerServiceApplication.java
• Right-click → Run

Option 2: Using Maven

./mvnw spring-boot:run

Option 3: Build & Run the JAR

./mvnw clean package
java -jar target/CustomerManagerService-0.0.1-SNAPSHOT.jar

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📫 API Endpoints

🔹 POST /customers

Adds multiple customers at once.

Requirements:

• Must include at least 2 customers

• Each customer must have:

• firstName, lastName (non-empty)

• age between 10–90

• Sequentially increasing id

[
  {
    "firstName": "Leia",
    "lastName": "Ray",
    "age": 25,
    "id": 1
  },
  {
    "firstName": "Frank",
    "lastName": "Anderson",
    "age": 30,
    "id": 2
  }
]

🔹 GET /customers

Returns the list of all customers, sorted by :

• lastName
• then firstName

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📁 Branch Summary

Branch	Description
main (this one)	🖥️ Local development with file-based persistence
cloud-integration	☁️ Deployed to AWS Lambda with DynamoDB storage

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📝 Design Decisions & FAQs

1. Why did you choose Spring Boot?

Spring Boot offers:

• Fast setup and built-in support for REST APIs

• Strong testing ecosystem

• Auto-configuration and cloud-native features

• Easy extensibility for GCP, AWS, or Docker

• It allowed rapid delivery with a scalable, professional structure.

2. Why file-based persistence?

File persistence allows:

• Retaining state across server restarts

• Avoiding the complexity of database setup

• Easy cloning and testing by reviewers

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Future Improvements

• Replace file persistence with DynamoDB or GCS
• Add Swagger/OpenAPI documentation
• Add CI/CD pipeline (GitHub Actions)
• Implement request throttling/rate-limiting
• Extend simulator with CLI flags and metrics