Java-to-.NET AWS Migration Demo

Live Demo (Swagger UI)

A demonstration project showcasing the migration of a Java Spring Boot application to .NET 8, with AWS S3 integration for image storage.

Project Overview

This project contains two implementations of the same Product Catalog REST API:

• java-original/ - Original Java 17 / Spring Boot 3.x implementation
• dotnet-migrated/ - Migrated .NET 8 / ASP.NET Core implementation

Both applications provide identical REST API endpoints and functionality, demonstrating practical enterprise migration patterns.

Features

• CRUD operations for products (GET, POST, PUT, DELETE)
• Image upload/download via AWS S3
• In-memory data storage
• LocalStack support for local development (no AWS account required)

API Endpoints

Method	Endpoint	Description
GET	/api/products	List all products
GET	/api/products/{id}	Get product by ID
POST	/api/products	Create new product
PUT	/api/products/{id}	Update product
DELETE	/api/products/{id}	Delete product
POST	/api/products/{id}/image	Upload product image
GET	/api/products/{id}/image	Download product image

Running the Applications

Prerequisites

• Java 17+ and Maven (for Java app)
• .NET 8 SDK (for .NET app)
• Docker (optional, for LocalStack)

Start LocalStack (Optional)

For local S3 testing without an AWS account:

docker run -d -p 4566:4566 localstack/localstack

# Create the bucket
aws --endpoint-url=http://localhost:4566 s3 mb s3://product-catalog-images

Java Application

cd java-original
mvn clean compile
mvn spring-boot:run

The API will be available at http://localhost:8080

.NET Application

cd dotnet-migrated
dotnet restore
dotnet build
dotnet run --project ProductCatalog.Api

The API will be available at http://localhost:5000 (or as shown in console output)

Testing the API

Create a Product

curl -X POST http://localhost:8080/api/products \
  -H "Content-Type: application/json" \
  -d '{"name": "Widget", "description": "A useful widget", "price": 29.99}'

List All Products

curl http://localhost:8080/api/products

Upload Product Image

curl -X POST http://localhost:8080/api/products/{id}/image \
  -F "file=@/path/to/image.jpg"

Configuration

Java (application.properties)

aws.access-key-id=${AWS_ACCESS_KEY_ID:test}
aws.secret-access-key=${AWS_SECRET_ACCESS_KEY:test}
aws.s3.region=${AWS_REGION:us-east-1}
aws.s3.bucket-name=${S3_BUCKET_NAME:product-catalog-images}
aws.s3.endpoint=${AWS_S3_ENDPOINT:http://localhost:4566}

.NET (appsettings.json)

{
  "AWS": {
    "AccessKeyId": "test",
    "SecretAccessKey": "test",
    "Region": "us-east-1",
    "S3": {
      "BucketName": "product-catalog-images",
      "Endpoint": "http://localhost:4566"
    }
  }
}

Project Structure

java-to-dotnet-aws-demo/
├── java-original/
│   ├── src/main/java/com/demo/productcatalog/
│   │   ├── ProductCatalogApplication.java
│   │   ├── controller/ProductController.java
│   │   ├── model/Product.java
│   │   ├── service/ProductService.java
│   │   └── service/S3StorageService.java
│   ├── src/main/resources/application.properties
│   └── pom.xml
├── dotnet-migrated/
│   ├── ProductCatalog.Api/
│   │   ├── Controllers/ProductController.cs
│   │   ├── Models/Product.cs
│   │   ├── Services/ProductService.cs
│   │   ├── Services/S3StorageService.cs
│   │   ├── Program.cs
│   │   └── appsettings.json
│   └── ProductCatalog.sln
└── docs/
    └── migration-guide.md

Documentation

See docs/migration-guide.md for detailed migration patterns and decisions.