There are basically 3 ways in spring to inject a dependency to the target class. You need to understand the difference first to understand what you need to achieve.

1. Field Injection:

   @Service
   public class StudentService {
     @Autowired
     private StudentRepository studentRepo;
      // complete service code using studentRepo
   }
   

   Field injection can be achieved using Spring by adding the @Autowired annotation to a class field. And what does @Autowired do? @Autowired is an annotation provided by Spring that allows the automatic wiring of the dependency. When applied to a field, method, or constructor, Spring will try to find a suitable dependency of the required type and inject it into the target class.

2. Setter Injection:

   @Service
   @Transactional
   public class UserService {
       private UserRepository userRepository;        
   
       @Autowired // Setter Injection
       public void setUserRepository(UserRepository userRepository) {
           this.userRepository = userRepository;
       }
   
       ...
   } 
   

   One more method to do Dependency Injection using Spring is by using setter methods to inject an instance of the dependency.

3. Constructor Injection:

   @Service
   @Transactional
   public class StudentService {
       private final StudentRepository studentRepo;
   
        // Dependency being injected through constructor
       public StudentService(StudentRepository studentRepo) {
                this.studentRepo = studentRepo;
       }
        ...
   }
   

   The final one is Constructor Injection. In OOP we create an object by calling its constructor. If the constructor expects all required dependencies as parameters, then we can be 100% sure that the class will never be instantiated without having its dependencies injected.

Now the confusing part for you is the @AllArgsConstructor annotation provided by the Lombok library. What this annotation does is that it simply creates a constructor of the class with all the available member fields of that class. So basically this annotation does the same thing what can be achieved by the constructor injection with a simple annotation. But remember the Field injection, Setter injection & Constructor injection are not the same & used on different scenarios. you can refer this link for more details - https://docs.spring.io/spring-framework/reference/core/beans/dependencies/factory-collaborators.html#beans-constructor-vs-setter-injection