Springbootapplication annotation

What is @springboot application annotation?

The @springbootapplication annotation is used to create simple spring boot applications. We need to add several annotations to our Application class or Main class to create a spring boot application. 

The @SpringBootApplication annotation is a combination of @EnablAutoConfiguration,@Configuration, and @ComponentScan.

The springbootapplication annotation helps the developers to mark configuration classes. The main three features of a springbootapplication annotation are as follows:

1. @EnablAutoConfiguration: Because of this feature, the application automatically produces and registers bean methods depending on both the jar files on the included classpath and the beans we define.

Example:

@Configuration
@EnableAutoConfiguration

//Application Class or Main Class
public class Main {

    //Main method
    public static void main(String[] args) {
        SpringApplication.run(Main.class, args);
    }
}

2. @Configuration: It tries to configure your Spring application automatically based on the jar dependencies you provided. You can use properties files, YAML files, environment variables, and command-line arguments to externalise configuration.

Example:

@Configuration

//Application Class or Main Class
public class Main {

    //Main method
       
    public static void main(String[] args) {         
        SpringApplication.run(Main.class, args);     
    }


        
    @bean
    // bean method's name or id
            public CN cnBean() {             // Returning the CN object
               
        return new CN();   
    }

3. @ComponentScan: When searching for components in Spring, the @ComponentScan annotation is used to define packages.

Example:

@Configuration
@ComponentScan

//Application Class or Main Class
public class Main{

 //Main method
    public static void main(String[] args) {
          SpringApplication.run(Main.class, args);
      }
}

Spring Boot SpringApplication Class

The Spring Boot SpringApplication class is a central component of the Spring Boot framework. It is used to bootstrap and launch a Spring application from a Java main method. The SpringApplication class automatically performs a number of tasks, including:

• Creating an ApplicationContext instance
   
• Scanning for configuration classes
   
• Registering command line arguments as Spring properties
   
• Refreshing the ApplicationContext
   
• Triggering any CommandLineRunner beans
   

To use the SpringApplication class, we need to create an instance of it and call the run() method. The run() method takes a list of arguments as input, which is used to configure the application.

 The following code example shows how to bootstrap and launch a simple Spring Boot application:

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

How to Implement @springboot application annotation?

An application or main class with the @SpringBootApplication annotation is required to run a Spring Boot application. The syntax is as follows:

package example;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;


@SpringBootApplication 
// works same as @EnableAutoConfiguration, @Configuration, and @ComponentScan.


public class Application {


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

The above code simply calls the SpringApplication.run() method. This launches the embedded beans and launches the Spring application as separate applications. One can place this code in the root package. It will help in component scanning and searching for beans in every sub-package.

Optional Parameters

The @SpringBootApplication annotation accepts the following parameters:

• Class<?>[] exclude: Make certain auto-configuration classes irrelevant by excluding them.
   
• Class<?>[] scanBasePackageClass: A type-safe alternative to scanBasePackages() for providing the packages to search for annotated components is scanBasePackageClass.
   
• String[] excludeName:  This parameter excludes the application of a particular auto-configuration class name.
   
• String[] scanBasePackages: This parameter is used to search for annotated components using scanBasePackages.

Optional Features

The @SpringBootApplication annotation offers aliases to modify the @EnableAutoConfiguration @Configuration and @ComponentScan's attributes. We can replace the springbootapplication annotation with any of these annotations, but none of these features is required. For example, you can use the springbootapplication annotation without the @ComponentScan method.

Here is the code for implementing the springbootapplication annotation without the @ComponentScan method.

package example;
import org.springframework.boot.SpringApplication;

import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ComponentScan;



@Configuration
@EnableAutoConfiguration 
//Not using the @ComponentScan

@Import({ FirstConfig.class, AnotherConfig.class }) 
//User-defined annotations are imported explicitly 
public class Main{
    public static void main(String[] args) {
        SpringApplication.run(Main.class, args);
    }
}

Frequently Asked Questions

What is the use of SpringBootApplication annotation?

The SpringBootApplication annotation is a meta-annotation in Spring Boot that combines Configuration, EnableAutoConfiguration, and ComponentScan. It simplifies application setup by configuring Spring Beans, enabling auto-configuration, and scanning for components in the specified package.

What is the difference between @Configuration and @SpringBootApplication?

@Configuration is a Spring annotation used to define application configuration classes manually, while @SpringBootApplication is a higher-level annotation in Spring Boot that includes @Configuration and provides additional features like auto-configuration and component scanning.

How does @SpringBootApplication work internally?

This annotation combines three functionalities:

1. @EnableAutoConfiguration: Enables Spring Boot's magic configuration, automatically setting up beans based on libraries on your classpath.
2. @ComponentScan: Scans your package and sub-packages for classes annotated with Spring stereotypes (@Component, @Service, etc.), registering them as beans.
3. @SpringBootConfiguration: Marks the class as a configuration class, allowing you to define additional beans or configurations.

Is @SpringBootApplication mandatory?

Yes, it's effectively mandatory for Spring Boot applications. It provides the core features for auto-configuration, component scanning, and enabling extra configurations in your main class. You could achieve similar functionality manually with separate annotations, but @SpringBootApplication simplifies it.

Conclusion

In this article, we discussed the Springbootapplication annotation. We discuss the implementation with optional parameters and features. 

We hope this article helps you. You can visit more articles related to Spring Boot.

• Spring Boot Hello World Example.
• Spring Boot Annotations.
• spring mvc vs spring boot

Happy Reading!!