Spring Boot 3 Web Client + gRPC + JPA/H2 1v1 Match Lab

Overview

This GitHub Classroom lab uses:

• Spring Boot 3.5.14 for the game server
• Spring Boot 3 web client for the browser interface
• gRPC + Protobuf between the web client module and the game server module
• Spring Data JPA for persistence
• File-based H2 database for saved matches

This version does not use JavaFX or FXML.

The browser talks to the game-client Spring Boot app using normal HTTP/JSON. The game-client then calls the game-server through gRPC. The game-server persists matches with JPA/H2.

Architecture

Browser
  ↓ HTTP/JSON
game-client Spring Boot web app
  ↓ gRPC/Protobuf
game-server Spring Boot gRPC service
  ↓ Spring Data JPA
file-based H2 database

Modules

Module	Purpose
game-server	Spring Boot 3 app hosting the gRPC service and persisting matches
game-client	Spring Boot 3 web app serving HTML/CSS/JS and proxying calls to gRPC

Build

From the project root:

mvn clean install

This generates Java classes from:

game-server/src/main/proto/game_service.proto
game-client/src/main/proto/game_service.proto

Run the Spring Boot 3 gRPC Server

Terminal 1:

cd game-server
mvn spring-boot:run

Expected output:

Spring Boot 3 gRPC Game Server started on port 50051

Run the Spring Boot 3 Web Client

Terminal 2:

cd game-client
mvn spring-boot:run

Open:

http://localhost:9091

Persistence

The server persists matches using Spring Data JPA and H2.

File	Purpose
MatchEntity.java	JPA entity stored in the database
MatchRepository.java	Spring Data repository for saved matches
game-server/src/main/resources/application.properties	Configures file-based H2
.gitignore	Prevents local database files from being committed

The database URL is:

spring.datasource.url=jdbc:h2:file:./data/game-server-db

Local database files are created under:

game-server/data/

These files should not be committed.

Important Design Choices

Removed Feature	Replacement
JavaFX/FXML desktop UI	Spring Boot web client with HTML/CSS/JS
Direct browser-to-server REST API	Browser calls web client; web client calls gRPC server
JSON between modules	gRPC/protobuf between modules
Player roles	Difficulty only
HP tracking	Server returns winner and loser
In-memory-only match storage	Spring Data JPA with file-based H2

Required TODOs

1. Verify the browser UI sends requests to the game-client REST facade.
2. Verify the game-client calls the game-server using gRPC.
3. Verify completed matches are saved through Spring Data JPA.
4. Verify match history loads from persisted JPA records.
5. Add one small web UI improvement.
6. Complete a Pull Request peer review.

Reflection Questions

1. What does the browser client do?
2. What does the game-client Spring Boot app do?
3. What does the game-server Spring Boot app do?
4. Why does this project still use gRPC if the UI is web-based?
5. What data is sent in JoinMatchRequest?
6. What data is returned in MatchResultResponse?
7. What is the purpose of MatchEntity?
8. What is the purpose of MatchRepository?
9. Why are H2 database files ignored by Git?
10. What did your peer reviewer suggest?
11. What did you change after peer review?