Spring Annotaions

Controller

@Controller = It indicates that the class is responsible for handling incoming HTTP requests.

RestController

@RestController = controller + ResponseBody.

Component

@Component = This indicates the class is a “Spring bean/Component” or Tells spring container to automatically create spring bean and manages it. ( no need to create object for the class with new keyword, spring automatically creates bean for it)

Example

@Component
public class Pizza {
	public String getPizza(){
		return "hello pizza";
	}
}

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

Run method returns the application context object i.e application context acts as a spring IOC container and the component creates the spring bean for the pizza class and that bean is already in the IOC container.
Get pizza bean

@SpringBootApplication
public class Main {
	public static void main(String[] args){
		var context = SpringApplication.run(Main.class,args);
		Pizza pizza = context.getBean(Pizza.class);
		System.out.println(pizza.getPizza());
	}
}

we can provide specific bean name, @Component(pizzaDemo);

Autowired

@Autowired = This annotation is used to inject the bean automatically.

Instead of creating object for ourself by adding new keyword. with component we can create the bean and with the Autowired we can initialize the bean automatically.
Check PizzaController class file for three different way to have the Autowired annotations i.e Constructor based, setter, and annotations based.

Qualifier

@Qualifier = This annotation helps to choose which bean to use for the Autowired