In this quick article, we will discuss one important Spring interview question that is what Is the use of @Autowired annotation?

What Is the Use of @Autowired Annotation?

We can use the @Autowired to mark a dependency which Spring is going to resolve and inject. We can use this annotation with a constructor, setter, or field injection.

Constructor Injection:

@RestController
public class CustomerController {
    private CustomerService customerService;
 
    @Autowired
    public CustomerController(CustomerService customerService) {
        this.customerService = customerService;
    }
}

Setter Injection:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class CustomerController {
    private CustomerService customerService;
 
    @Autowired
    public void setCustomerService(CustomerService customerService) {
        this.customerService = customerService;
    }
}

Field Injection:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class CustomerController {
    @Autowired
    private CustomerService customerService;
}

Learn more about @Autowired annotation at Spring @Autowired Annotation with Example

References

Spring @Autowired Annotation with Example