[Spring] Spring Stereotype Annotations - Component and more

Spring Stereotype Annotations - Component and more

/ @Component / @Repository / @Service / @Controller /

• @Component - Generic annotation applicable for any class
  • Base for all Spring Stereotype Annotations
  • Specializations of @Component:
    • @Service - Indicates that an annotated class has business logic
    • @Controller - Indicates that an annotated class is a “Controller” (e.g. a web controller)
      • Used to define controllers in your web applications and REST API
    • @Repository - Indicates that an annotated class is used to retrieve and/or manipulate data in a database
• What should you use?
  • (RECOMMENDATION) Use the most specific annotation possible
  • Why?
    • By using a specific annotation, you are giving more information to the framework about your intentions
    • You can use AOP at later point to add additional behavior
      • Example : For @Repository, Spring automatically wires in JDBC Exception translation features

예제

import org.springframework.stereotype.Component;  
import org.springframework.stereotype.Repository;  
  
//@Component  
@Repository  <-
public class MySQLDataService implements DataService{  
    @Override  
    public int[] retrieveData() {  
  
        return new int[] {1, 2, 3, 4, 5};  
    }  
}

import org.springframework.stereotype.Component;  
import org.springframework.stereotype.Service;  
  
import java.util.Arrays;  
//@Component  
@Service  <-
public class BusinessCalculationService {  
    private DataService dataService;  
    public BusinessCalculationService(DataService dataService){  
        super();  
        this.dataService = dataService;  
    }  
    public int findMax() {  
        return Arrays.stream(dataService.retrieveData())  
                .max().orElse(0);  
    }  
}