Event-Driven Design Demo

A Spring Boot demonstration of application submission with a transactional outbox pattern. Submissions are persisted to H2 and an Avro-encoded outbox record is written in the same transaction; Kafka publishing is planned via a background outbox processor.

Tech stack

• Java 25
• Spring Boot 3.5.14
• Spring Data JPA + H2 (dev) / PostgreSQL (prod target)
• Apache Avro (in-repo schemas, Maven code generation)
• Maven

Planned: Spring Kafka, outbox processor, Resilience4J circuit breaker, DLQ admin API.

Quick start

./mvnw spring-boot:run

On Windows:

mvnw.cmd spring-boot:run

The app starts on port 8080 with an in-memory H2 database initialized from schema.sql and data.sql.

Submit an application

curl -X POST http://localhost:8080/applications \
  -H "Content-Type: application/json" \
  -d '{"firstName":"Jane","lastName":"Doe"}'

Example response:

{
  "applicationId": "...",
  "correlationId": "...",
  "timestamp": "2026-06-06T12:00:00.123456789Z",
  "status": "SUBMITTED"
}

H2 console

Browse the database at http://localhost:8080/h2-console:

• JDBC URL: jdbc:h2:mem:testdb
• Username: sa
• Password: (empty)

Documentation

Document	Description
docs/01-requirements.md	Requirements and approved decisions
docs/02-architecture.md	Architecture, data flows, implementation status
docs/03-domain-model.md	Entities, schema, Avro, persistence
docs/04-api-design.md	REST API contract and DTOs

Implementation status

Component	Status
POST /applications	Done
Transactional outbox write (Avro payload)	Done
Outbox processor → Kafka	Not started
Retry / DLQ / cleanup jobs	Not started
DLQ admin / replay API	Not started

See docs/02-architecture.md for the full backlog.

Project layout

src/main/java/.../
  controller/     REST endpoints
  service/        Business logic + outbox write
  repository/     Spring Data JPA
  entity/         Application, Outbox, OutboxDlq
  dto/            Request/response DTOs
  exception/      Global exception handling

src/main/resources/
  avro/           Avro schema files
  schema.sql      H2 table definitions
  data.sql        Sample seed data
  application.yml Spring Boot configuration

Build and test

./mvnw clean verify

Avro Java classes are generated at build time into target/generated-sources/avro.