Spring Boot Core Features

Spring Boot simplifies Spring application development through three key features:

1. Auto-configuration: Automatically configures Spring applications based on dependencies present
2. Starter Dependencies: Bundles common dependencies for specific functionalities
3. Production-ready Featrues: Includes metrics, health checks, and externalized configuration

Building a Basic Spring Boot Application

Implementation Steps:

1. Create Maven project with parent POM:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.5.4</version>
</parent>

2. Add web starter dependency:

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

3. Create controller:

@RestController
public class GreetingController {
    @GetMapping("/greet")
    public String greet() {
        return "Welcome to Spring Boot";
    }
}

4. Create main appplication class:

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Configuration Management

Spring Boot supports multiple configuration formats with following priorities:

1. .properties
2. .yml
3. .yaml

YAML Syntax:

app:
  server:
    port: 9090
    host: localhost
  features: [logging, metrics]

Accessing Configuration:

1. Using @Value:

@Value("${app.server.port}")
private int serverPort;

2. Using Environment:

@Autowired
private Environment env;

String host = env.getProperty("app.server.host");

3. Using @ConfigurationProperties:

@Component
@ConfigurationProperties(prefix = "app")
public class AppConfig {
    private Server server;
    private List<String> features;
    // Getters and setters
}

Profile Management

Profile Activation Methods:

1. Configuration file:

spring.profiles.active=prod

2. Command line:

java -jar app.jar --spring.profiles.active=dev

Integration Testing

Test Setup:

1. Add test dependencies:

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

2. Create test class:

@SpringBootTest
class ApplicationTests {
    @Test
    void contextLoads() {
        // Test logic
    }
}

Database Integration

MyBatis Configuration:

1. Add dependencies:

<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.0</version>
</dependency>

2. Configure datasource:

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/db
    username: user
    password: pass

3. Create repository:

@Mapper
public interface UserRepository {
    @Select("SELECT * FROM users")
    List<User> findAll();
}

Redis Integration

1. Add Redis starter:

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

2. Configure Redis:

spring:
  redis:
    host: localhost
    port: 6379

3. Use RedisTemplate:

@Autowired
private RedisTemplate<String, String> redisTemplate;

public void storeData(String key, String value) {
    redisTemplate.opsForValue().set(key, value);
}