Define the Key Components of Spring Boot

Key Components of Spring Boot

1. SpringApplication

• Explanation: The `SpringApplication` class provides a convenient way to bootstrap a Spring application from a main method.
• It starts the embedded server, creates the Spring application context, and performs other startup activities.
• Benefit: Simplifies the process of running Spring applications.

2. @SpringBootApplication

• Explanation: A convenience annotation that combines `@Configuration`, `@EnableAutoConfiguration`, and `@ComponentScan` annotations. It is typically placed on the main class to enable these features.
• Benefit: Reduces boilerplate code by combining commonly used annotations.

3. Application Properties

1. Explanation: Configuration properties are stored in files such as `application.properties` or `application.yml`, allowing for externalized configuration of the application.
2. Benefit: Simplifies configuration management and allows for different configurations for different environments.

4. Spring Boot Starters

1. Explanation: Starters are a set of convenient dependency descriptors that you can include in your application. For example, `spring-boot-starter-web` includes dependencies for developing web applications.
2.  Benefit: Simplifies dependency management by bundling commonly used dependencies.

5. Spring Boot Actuator

• Explanation: Provides built-in endpoints to help monitor and manage the application. It includes features like metrics, health checks, and more.
• Benefit: Enhances the monitoring and management of applications.

6. Embedded Server

• Explanation: Spring Boot applications can run as standalone applications with an embedded server such as Tomcat, Jetty, or Undertow.
• Benefit: Simplifies deployment and testing by eliminating the need for external web servers.

Examples

MainApplication.java
```java
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

In this example:

• SpringApplication.run: Boots the application, creating the Spring context and starting the embedded server.

2. @SpringBootApplication

MainApplication.java
```java
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

In this example:

• @SpringBootApplication: Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan into one annotation.

3. Application Properties

application.properties
```properties
server.port=8081
spring.datasource.url=jdbc:mysql://localhost:3306/mydb
spring.datasource.username=root
spring.datasource.password=password
```

In this example:

• External Configuration: Configures the server port and database connection properties.

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

In this example:

• spring-boot-starter-web: Bundles dependencies for creating web applications.

5. Spring Boot Actuator

application.properties
```properties
management.endpoints.web.exposure.include=health,info
```

HealthController.java
```java
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HealthController {

    @GetMapping("/health")
    public String health() {
        return "Application is up and running";
    }
}
```

In this example:

• Actuator Endpoints: Configures health and info endpoints for monitoring.

6. Embedded Server

application.properties
```properties
server.port=8081
```

MainApplication.java
```java
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

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

In this example:

• Embedded Server: Configured to run on port 8081 instead of the default 8080.

Summary of key components

• Spring Boot: Simplifies application development with key components like SpringApplication, @SpringBootApplication, application properties, starters, actuator, and embedded servers.
• Advantages: Streamlines development, configuration management, monitoring, and deployment.

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