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Spring Boot Setup

Beginner

Core & Setup

Spring Boot eliminates boilerplate setup through auto-configuration and starter dependencies. A production-ready app can be running in under 5 minutes with the right project structure.

Overview

Spring Initializr (start.spring.io) generates a Maven or Gradle project with a parent POM that manages all dependency versions via the spring-boot-dependencies BOM. Starters (spring-boot-starter-web, spring-boot-starter-data-jpa, etc.) bundle related libraries with pre-tested compatible versions. Auto-configuration then inspects the classpath and registered beans to configure the application without any XML — if spring-boot-starter-web is on the classpath, Tomcat, DispatcherServlet, and Jackson are configured automatically.

pom.xml & Starter Dependencies

The spring-boot-starter-parent POM provides sensible defaults: Java version, encoding, plugin configuration, and dependency management via spring-boot-dependencies BOM. You only specify version once (the Spring Boot version) and all starters use compatible library versions.

XML — pom.xml with common starters

<!-- pom.xml — minimal Spring Boot web app -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.3.0</version>
</parent>

<dependencies>
    <!-- Web: Tomcat + Spring MVC + Jackson -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- JPA: Hibernate + Spring Data -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>

    <!-- PostgreSQL driver -->
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <scope>runtime</scope>
    </dependency>

    <!-- Test: JUnit 5, Mockito, MockMvc -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <!-- Builds executable fat JAR with java -jar -->
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

Project Structure

Spring Boot has a conventional package structure. The main class with @SpringBootApplication should be in the root package — @ComponentScan will then automatically pick up all classes in sub-packages. Placing it in a sub-package means you need explicit basePackages.

Project structure — conventional layout

src/
└── main/
    ├── java/
    │   └── com/aicancode/toolhub/           ← root package
    │       ├── ToolhubApplication.java       ← @SpringBootApplication here
    │       ├── controller/                   ← @RestController classes
    │       ├── service/                      ← @Service classes
    │       ├── repository/                   ← @Repository / JPA interfaces
    │       ├── model/                        ← @Entity classes
    │       ├── dto/                          ← request/response POJOs
    │       ├── config/                       ← @Configuration classes
    │       └── exception/                    ← custom exceptions + @ControllerAdvice
    └── resources/
        ├── application.yml                   ← main config
        ├── application-dev.yml               ← dev overrides
        ├── application-prod.yml              ← prod overrides
        └── db/migration/                     ← Flyway SQL scripts

// Main class — @SpringBootApplication in root package
@SpringBootApplication
public class ToolhubApplication {
    public static void main(String[] args) {
        SpringApplication.run(ToolhubApplication.class, args);
    }
}

Key Points to Remember

1spring-boot-starter-parent manages all dependency versions — never specify library versions manually.
2Starters bundle related libraries with compatible versions; you pick the feature, Spring picks the versions.
3@SpringBootApplication must be in the root package for @ComponentScan to find all sub-packages.
4Auto-configuration is conditional — it backs off when you declare your own beans.
5spring-boot-maven-plugin produces a fat executable JAR runnable with java -jar.
6Use application-{profile}.yml for environment-specific overrides (dev, prod, test).

Interview Questions

What does spring-boot-starter-parent provide?

EasyTCS

What is a Spring Boot Starter and how does it differ from a regular dependency?

EasyWipro

Why should @SpringBootApplication be in the root package?

MediumInfosys

How would you exclude a specific auto-configuration class?

MediumAmazon

What is the spring-boot-dependencies BOM and why is it useful?

MediumAtlassian

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