🗂️

Spring Project Layout

How a typical Spring Boot application is organized (the BookVault shape).

Package by feature

com.bookvault
├── BookVaultApplication.java
├── catalog/      (Book domain)
├── lending/      (Members & Loans)
├── security/     (auth & roles)
├── common/       (shared: error handling)
└── config/       (OpenAPI, async, …)

group by domain area, not by layer

Inside a feature package

Entity@Entity mapped to a table (Book.java)
RepositorySpring Data interface (BookRepository)
Servicebusiness logic, @Transactional (BookService)
ControllerREST endpoints (BookController)
dto/request/response records, kept off the entity
*Exceptiondomain errors → ProblemDetail

Resources

```
src/main/resources/application.yml
```
externalized config
```
…/application-<profile>.yml
```
per-environment overrides
```
…/db/migration/V1__*.sql
```
Flyway schema migrations
```
src/test/java/…
```
mirrors main; the test pyramid

Build & run

```
pom.xml  /  build.gradle
```
dependencies & plugins
```
./mvnw spring-boot:run
```
run in dev
```
./mvnw test
```
unit + slice + integration tests
```
./mvnw package
```
build the executable jar