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Java Final Project: Distributed Microservice System

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Java Final Project: Distributed Microservice System
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Java Final Project: Distributed Microservice System

1. The Architecture: The "Cloud-Native" Blueprint

Our system consists of four independent services:

  1. Gateway Service: The entry point. Handles security and rate limiting.
  2. User Service: Manages profiles and authentication.
  3. Inventory Service: Manages product stock levels.
  4. Notification Service: Sends emails asynchronously via Kafka.
mermaid




2. Event-Driven Inventory: The Kafka Heartbeat


When a user buys a product, we don't call the "Notification Service" directly.


    

  • The Inventory Service simply publishes an OrderPlaced event to Kafka.
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  • The Notification Service is "Listening." It sees the event and sends the email whenever it's not busy.
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  • Benefit: If the Notification Service is DOWN, the user can still buy the product! The email will just be sent $5$ minutes later when the service restarts. This is Resilience.
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3. Distributed Resilience: The Circuit Breaker


What if the User Service becomes slow?
We implement Resilience4j in the Gateway. If the User Service fails 50% of its calls, the Gateway "Cuts the connection." For the next $30$ seconds, it returns a cached response or a "Try again soon" message. This prevents the "Traffic Jam" from building up and crashing the entire system.




4. Deployment: The Kubernetes Orchestration


We package each service as a GraalVM Native Image (Module 193).


    

  • Size: Each image is only ~30MB.
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  • K8s: We deploy them to a local Kubernetes cluster (Minikube).
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  • Auto-Scaling: We configure K8s to "Spin up" a second copy of the Inventory Service if the CPU usage goes above 70%.
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Frequently Asked Questions


Is this overkill for most apps?
YES. Ninety percent of apps should be a Monolith. However, for companies like Uber, Netflix, or Amazon, this architecture is the ONLY way to survive. By learning it, you prepare yourself for the highest-paying, most challenging roles in the industry.


What is the 'Final Assessment'?
Beyond the code, you must produce a System Design Document. You must explain: "Why did you choose Kafka instead of RabbitMQ?" and "How do you handle a database failure?" This prove that you aren't just a coder, but an Architect.




Key Takeaway


You have graduated. By building a distributed, event-driven ecosystem, you have mastered the most complex and powerful tools in the Java world. You possess the skills to build, protect, and scale the software that the world's largest companies rely on every day. Welcome to the elite world of the Java Enterprise Architect.




You have completed the Java Enterprise Mastery — masters of the enterprise.