Spring Boot

🚀 What is Spring Boot?

Spring Boot simplifies Spring application development by providing auto-configuration, embedded servers, and production-ready features. It eliminates boilerplate configuration and enables rapid development with minimal setup required.


// Complete REST API in just a few lines
@SpringBootApplication
@RestController
public class Application {
    
    @GetMapping("/hello")
    public String hello() {
        return "Hello Spring Boot!";
    }
    
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Spring Boot Features

⚙️

Auto-Configuration

Automatic setup based on dependencies

@SpringBootApplication
// Auto-configures everything!

📦

Embedded Server

Built-in Tomcat, Jetty, or Undertow

// No external server needed
java -jar myapp.jar

🎯

Starters

Pre-configured dependency bundles

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

📊

Actuator

Production-ready monitoring features

// Health checks, metrics, etc.
/actuator/health

🔹 Creating a Spring Boot Project

Start with Spring Initializr or create manually:

<!-- pom.xml -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>3.2.0</version>
</parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
</dependencies>

Run with:

mvn spring-boot:run

Server starts on http://localhost:8080

🔹 REST API Example

Build a complete REST API quickly:

@RestController
@RequestMapping("/api/users")
public class UserController {
    
    private List<User> users = new ArrayList<>();
    
    @GetMapping
    public List<User> getAllUsers() {
        return users;
    }
    
    @PostMapping
    public User createUser(@RequestBody User user) {
        user.setId(System.currentTimeMillis());
        users.add(user);
        return user;
    }
    
    @GetMapping("/{id}")
    public User getUser(@PathVariable Long id) {
        return users.stream()
            .filter(u -> u.getId().equals(id))
            .findFirst()
            .orElse(null);
    }
}

API Endpoints:

GET /api/users - List all users

POST /api/users - Create user

GET /api/users/1 - Get user by ID

🔹 Configuration Properties

Configure your application easily:

# application.properties
server.port=8081
spring.application.name=my-app
logging.level.com.example=DEBUG

# Database configuration
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.hibernate.ddl-auto=create-drop

🔸 Using @ConfigurationProperties

@ConfigurationProperties(prefix = "app")
@Component
public class AppProperties {
    private String name;
    private String version;
    
    // getters and setters
}