Spring Boot Project Anatomy & Package Design

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catalog-service/
├── pom.xml
├── mvnw
├── .mvn/wrapper/
└── src/
    ├── main/
    │   ├── java/com/acme/catalog/
    │   │   ├── CatalogApplication.java   # root scan package
    │   │   ├── product/
    │   │   │   ├── ProductController.java
    │   │   │   ├── ProductService.java
    │   │   │   ├── Product.java
    │   │   │   └── ProductRepository.java
    │   │   └── shared/config/
    │   └── resources/
    │       ├── application.yml           # classpath config
    │       ├── db/migration/              # Flyway SQL
    │       ├── static/                    # directly served assets
    │       └── templates/                 # server-rendered templates
    └── test/
        ├── java/com/acme/catalog/product/ # mirrors production package
        └── resources/application-test.yml

target/                                    # generated; do not commit

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// com.acme.catalog.product
// Public application API for the product feature.
package com.acme.catalog.product;

// Keep implementation types package-private when possible:
// ProductController  -> HTTP adapter
// ProductService     -> transactional use cases
// Product            -> domain/persistence model
// ProductRepository  -> persistence boundary

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@Component
class SeedDataLoader {
    private final ResourceLoader resources;

    SeedDataLoader(ResourceLoader resources) {
        this.resources = resources;
    }

    String readSeedData() throws IOException {
        var resource = resources.getResource("classpath:seed/products.json");
        try (var input = resource.getInputStream()) {
            return new String(input.readAllBytes(), StandardCharsets.UTF_8);
        }
    }
}

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<!-- Root multi-module pom.xml -->
<modules>
  <module>catalog-api</module>   <!-- DTOs, events, and client interfaces -->
  <module>catalog-core</module>  <!-- Entities, repository ports, domain logic -->
  <module>catalog-app</module>   <!-- Spring Boot main class, web adapters, SQL -->
</modules>