gRPC Trading Platform

A Spring Boot + gRPC demo trading system built as a multi-module Maven project. It shows how to share protobuf contracts, expose gRPC services, call them from another service, and bridge gRPC to REST/SSE.

Highlights

• Shared protobuf contracts in one module
• gRPC server implementations for users and stock prices
• REST gateway that consumes gRPC services
• Unary RPCs and server-streaming RPCs
• H2-backed persistence for user data
• Integration tests for gRPC and SSE flows

Modules

Module	Responsibility
proto	Protobuf messages and generated gRPC classes
user-service	gRPC user service with H2 + JPA storage
stock-service	gRPC stock service with in-memory prices and live updates
aggregator-service	REST API that calls the gRPC services

Request flow

REST client -> aggregator-service -> gRPC -> user-service / stock-service

• aggregator-service handles HTTP requests.
• user-service stores users and portfolio items in H2.
• stock-service serves prices from memory and streams updates.

Tech stack

• Java 21
• Spring Boot 3.5
• gRPC
• Protocol Buffers
• Spring Data JPA
• H2 database

Main endpoints

REST API

Endpoint	Description
GET /user/{id}	Fetch user information
POST /trade	Buy or sell a stock
GET /stock/updates	Stream live stock updates as SSE

gRPC services

• user.UserService
  • GetUserInformation
  • TradeStock
• stock.StockService
  • GetStockPrice
  • GetPriceUpdates

Running the project

Build and test everything:

mvn clean test

Run a specific service:

mvn spring-boot:run -pl user-service
mvn spring-boot:run -pl stock-service
mvn spring-boot:run -pl aggregator-service

Notes

• user-service uses H2, so data resets when the app stops.
• stock-service keeps prices in memory, so its state also resets on restart.
• The project is intended as a learning and portfolio demo for gRPC in Spring Boot.