Reactive Microservices Spring Boot AWS Lambda

Source code for the ebook "Reactive Microservices with Spring Boot and AWS Lambda". A complete project with Spring Boot 4.1.0, Java 25, Project Reactor, and AWS Lambda. Production-ready with support for native compilation via GraalVM.

📖 Get the full ebook:

• 📚 Amazon Kindle
• 🛒 Hotmart
• 💳 Gumroad

🚀 Tech Stack

• Java 25 + Spring Boot 4.1.0 + Spring WebFlux (Ebook: Section 0.13, 0.14)
• Spring Cloud Function 5.0.3 (Spring Cloud 2025.1.2) (Ebook: Section 3.2)
• Project Reactor (Mono/Flux) (Ebook: Section 2.3)
• Spring Cloud Function + AWS Lambda (Ebook: Section 3.3, 3.4)
• GraalVM Native Image (native compilation) (Ebook: Section 4.2, 4.4)
• AWS SAM + LocalStack (local development) (Ebook: Section 1.5, 3.6)
• GitHub Actions (CI/CD) (Ebook: Section 6.6)
• Micrometer + Spring Actuator (observability) (Ebook: Section 6.4)

🏗️ Architecture

API Gateway HTTP API → AWS Lambda → Spring Cloud Function → Project Reactor
                                    ↓
                            CloudWatch Logs / DynamoDB / SQS

🚀 Quick Start

Requirements: Java 25, Gradle 9.6.1+ (bundled), Docker, AWS SAM CLI (Ebook: Section 1.2)

# Clone and build
git clone <repository-url>
cd reactive-microservices-aws-lambda-java25

# Use the Java 25 version (recommended)
git checkout v1.0.0-java25

# Or use the previous Java 21 version (reference only)
# git checkout v1.0.0-java21

./gradlew clean build  # Ebook: Section 1.4, 1.8

# Run tests
./gradlew test  # Ebook: Section 2.8

# Start the local application
./gradlew :lambda-core:bootRun  # Ebook: Section 1.6

💻 Local Development

# Start LocalStack
docker-compose up -d localstack  # Ebook: Section 1.5, 5.10

# Test with SAM
cd lambda-infra
sam build --template template.yaml  # Ebook: Section 3.6
sam local invoke "ReactiveFunction" --event events/hello.json  # Ebook: Section 3.6
sam local start-api  # Ebook: Section 3.6

🐳 Running with Docker

Application Image

# Build the multi-stage image (Java 25 + Spring Boot)
docker build -t reactive-lambda .

# Run the function as a WebFlux service on localhost (uses 8081 if 8080 is taken)
docker run --rm -d -p 8081:8080 --name reactive-lambda reactive-lambda

# Smoke test against the endpoint and actuators exposed on the container
curl -i "http://localhost:8081/hello?name=Marcos"
curl -i "http://localhost:8081/actuator/health"

Example response:

HTTP/1.1 200 OK
Content-Type: application/json
{"message":"ok","name":"Marcos","greeting":"Hello, Marcos!","timestamp":"2025-12-07T22:25:41.234Z"}

Containerized Tooling (Gradle + SAM)

# Bash / zsh
docker run --rm -it \
  -v ${PWD}:/workspace \
  -w /workspace \
  public.ecr.aws/sam/build-java25:latest \
  bash -lc "./gradlew test"

docker run --rm -it \
  -v ${PWD}:/workspace \
  -w /workspace \
  public.ecr.aws/sam/build-java25:latest \
  bash -lc "sam build --template lambda-infra/template.yaml && sam validate"

# PowerShell
docker run --rm -it `
  -v ${PWD}:/workspace `
  -w /workspace `
  public.ecr.aws/sam/build-java25:latest `
  bash -lc "./gradlew test"

docker run --rm -it `
  -v ${PWD}:/workspace `
  -w /workspace `
  public.ecr.aws/sam/build-java25:latest `
  bash -lc "sam build --template lambda-infra/template.yaml && sam validate"

☁️ Deploying to AWS

cd lambda-infra
sam deploy --guided  # Ebook: Section 3.7, 3.11.1

📖 See in the ebook:

• Section 3.7 (Deploying to AWS)
• Section 3.11.1 (Deploying with API Gateway)
• Section 4.8 (Deploying the native binary to AWS Lambda)

🧪 Testing

./gradlew test                    # All tests
./gradlew :lambda-core:test       # lambda-core only
./gradlew :lambda-tests:test      # Integration only

🎯 Native Compilation

export JAVA_HOME=/path/to/graalvm-jdk-25  # Ebook: Section 4.5.1
./gradlew :lambda-core:nativeCompile  # Ebook: Section 4.4, 4.8

📖 See in the ebook: Section 4 (Startup and performance optimization with GraalVM Native) for full details on configuration, optimizations, and deploying the native binary.

📊 Observability

# Health check
curl http://localhost:8080/actuator/health  # Ebook: Section 6.4

# Metrics
curl http://localhost:8080/actuator/metrics  # Ebook: Section 6.4

📖 See in the ebook:

• Section 6.3 (Structured logging)
• Section 6.4 (Custom metrics with Micrometer)
• Section 6.5 (Distributed tracing with AWS X-Ray)

🐛 Troubleshooting

Error: "Cannot find handler"

./gradlew clean build

LocalStack not responding

docker-compose restart localstack
curl http://localhost:4566/_localstack/health

GraalVM Native Build fails

export GRADLE_OPTS="-Xmx4g"
./gradlew clean :lambda-core:nativeCompile

📁 Project Structure

├── lambda-core/          # Main Lambda code (Ebook: Section 1.7, 3.9)
│   ├── src/main/java/com/example/lambda/
│   │   ├── FunctionConfig.java      # Ebook: Section 3.9.1
│   │   ├── HelloHandler.java        # Ebook: Section 3.9.2
│   │   ├── HelloController.java     # Ebook: Section 2.4, 2.5
│   │   ├── GlobalExceptionHandler.java  # Ebook: Section 3.10, 2.7
│   │   └── RequestValidator.java   # Ebook: Section 3.10.1
│   └── src/main/resources/
│       ├── application.yml          # Ebook: Section 1.9.1
│       ├── application-dev.yml       # Ebook: Section 1.9.2
│       └── application-prod.yml     # Ebook: Section 1.9.3
├── lambda-infra/         # SAM template (Ebook: Section 3.11)
│   ├── template.yaml     # Ebook: Section 3.11
│   └── events/           # Ebook: Section 3.6
├── lambda-tests/         # Integration tests (Ebook: Section 2.8)
└── buildSrc/             # Gradle conventions (Ebook: Section 1.4)
    └── src/main/kotlin/conventions.gradle.kts  # Ebook: Section 0.14, 1.4

📖 Cross-Reference Document: See REFERENCIAS_CRUZADAS_EBOOK_PROYECTO.md for a full mapping between the ebook and the project files.

🏷️ Versions and Tags

The project includes Git tags to make it easy to access different versions:

• v1.0.0-java25 (current): Full version migrated to Java 25

  • Java 25 LTS, Spring Boot 3.4.13, Gradle 9.2.1
  • AWS Lambda runtime: java25
  • Recommended for following the updated ebook

• v1.0.0-java21: Last version before the Java 25 migration

  • Java 21, Spring Boot 3.3.1
  • Useful for comparing changes or seeing the prior state

Using a Specific Version

# List all available versions
git tag -l

# Switch to the Java 25 version (recommended)
git checkout v1.0.0-java25

# Switch to the Java 21 version (reference only)
git checkout v1.0.0-java21

# See differences between versions
git diff v1.0.0-java21 v1.0.0-java25

# Go back to the latest version
git checkout main

📚 Resources

📖 Ebook

• 📚 Amazon Kindle
• 🛒 Hotmart
• 💳 Gumroad

🔗 Cross-References: This project is 100% aligned with the ebook. See REFERENCIAS_CRUZADAS_EBOOK_PROYECTO.md to navigate between the ebook and the source code.

Documentation

• Spring Boot (Ebook: Section 0.13, 1.4)
• Spring Cloud Function (Ebook: Section 3.2)
• AWS SAM (Ebook: Section 3.6, 3.11)
• Project Reactor (Ebook: Section 2.3)

💝 Support the Project

If this project has been useful to you:

• 📖 Get the full ebook - Amazon | Hotmart | Gumroad
• ☕ Buy Me a Coffee
• 💳 PayPal Donate
• ⭐ Star the repository

Thanks for your support! 🙏

🤝 Contributing

1. Fork the project
2. Create a branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📄 License

Copyright (c) 2025 Marcos Raimundo Lozina. All rights reserved.

This project is protected by copyright. See the LICENSE file for full details.

Usage: Personal and educational use only. Any commercial use requires prior authorization.

👤 Author

Marcos Raimundo Lozina

Created as a reference project for serverless reactive microservices with Spring Boot and AWS Lambda.