Folder Structure Overview

Spring Boot projects follow a layered and modular folder structure that organizes code, resources, and configuration files efficiently. This structure supports the layered architecture and keeps the project maintainable, scalable, and easy to navigate.

A typical Spring Boot project looks like this:

my-spring-app/
│
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/myapp/
│   │   │       ├── MySpringBootApplication.java   # Main application class
│   │   │       ├── controller/                   # Handles HTTP requests
│   │   │       ├── service/                      # Business logic layer
│   │   │       ├── repository/                   # Data access layer
│   │   │       ├── model/                        # Entities and domain objects
│   │   │       ├── dto/                          # Data Transfer Objects
│   │   │       └── config/                       # Java-based configuration classes
│   │   │
│   │   └── resources/
│   │       ├── application.properties / application.yml  # App configuration
│   │       ├── static/                           # CSS, JS, images
│   │       ├── templates/                        # View templates (Thymeleaf, JSP)
│   │       └── db/                               # SQL scripts or data initialization
│   │
│   └── test/
│       └── java/
│           └── com/example/myapp/               # Unit & integration tests
│
├── pom.xml (Maven) / build.gradle (Gradle)      # Build and dependency management
└── README.md                                    # Project description and documentation

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Folder Breakdown & Purpose

1. src/main/java

This folder contains all Java source code, organized according to the layered architecture:

• controller/ → Handles HTTP requests and returns responses (REST or MVC endpoints). Uses @RestController or @Controller.
• service/ → Contains business logic and orchestrates operations between layers. Annotated with @Service.
• repository/ → Manages database access using Spring Data JPA, JDBC, or other persistence frameworks. Annotated with @Repository.
• model/ → Entity classes and domain objects representing application data.
• dto/ → Data Transfer Objects for moving data between layers without exposing entities directly.
• config/ → Java-based configuration classes (e.g., Spring Security, custom beans).
• MySpringBootApplication.java → Main entry point annotated with @SpringBootApplication to bootstrap the application.

Key Points:

• Promotes modularity, maintainability, and testability.
• Keeps business logic separate from controllers and repositories.
• Follows Presentation → Service → Repository → Persistence pattern.

---

2. src/main/resources

This folder contains all non-Java resources, such as configuration files, templates, static assets, and SQL scripts:

• application.properties / application.yml → Configures database, server port, logging, and other application settings.
• static/ → Stores CSS, JS, images, and other frontend assets automatically served by Spring Boot.
• templates/ → HTML templates for web views (Thymeleaf, JSP, FreeMarker).
• db/ → Optional folder for SQL scripts or database initialization.
• messages.properties → Supports localization and internationalization (i18n).

Key Notes:

• Spring Boot auto-detects resources here at startup.
• Static and template files are served automatically by Spring MVC.
• Configuration files enable auto-configuration for database, logging, and server settings.

---

3. src/test/java

• Contains unit and integration tests for controllers, services, and repositories.
• Mirrors the main package structure to maintain consistency.

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4. Build Files

• pom.xml (Maven) or build.gradle (Gradle) → Manage project dependencies, plugins, and build configurations.

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Best Practices

• Follow a layered structure (Controller → Service → Repository → Model/DTO).
• Keep DTOs separate from entities to maintain clean architecture.
• Organize static and template resources logically.
• Use environment-specific properties (application-dev.properties, application-prod.properties).
• Keep main class and configuration files at the top level for easy access.

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Why This Structure Matters

• Modular & Maintainable: Each layer has a clear responsibility.
• Scalable: Add new features or layers without breaking existing code.
• Testable: Supports unit and integration testing efficiently.
• Beginner-Friendly: Standard structure simplifies understanding project flow.
• Production-Ready: Auto-configuration, embedded server, and logging make deployment easy.