@Component vs @Repository vs @Service in Spring

Shubhra SrivastavaMay 17th, 2019Last Updated: May 15th, 2019

5 1,182 2 minutes read

Introduction:

With Spring’s auto-scanning feature, it automatically detects various beans defined in our application. We usually annotate our beans using one of the available Spring annotations – @Component, @Repository, @Service, @Controller.

On detecting the bean, Spring simply registers it into the ApplicationContext.

In this quick tutorial, we’ll look at the difference between @Component, @Repository, and, @Service Spring annotations.

@Component:

We can use @Component annotation to mark a bean as a Spring-managed component. In other words, it’s a generic stereotype for any Spring-managed component.

We can enable an auto-scan using <context:component-scan> tag. During auto-scan, Spring will scan and register all beans marked with a @Component annotation:

@Component
public class Employee {
   ...
 
}

@Repository:

@Repository annotation is a specialization over @Component annotation:

@Component
public @interface Repository {
}

Since @Repository is a type of @Component, Spring also auto-scans and registers them.

@Repository is a stereotype for the persistence layer. Its job is to catch all persistence related exceptions and rethrow them as a Spring DataAccessException.

For this, we should configure PersistenceExceptionTranslationPostProcessor in our application context:

<bean class=
  "org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor"/>

This bean post processor adds an advisor to all beans marked with @Repository. The advisor’s responsibility is to translate the platform-specific exceptions to the Spring’s unified unchecked exceptions.

@Service:

Just like @Repository, @Service is another specialization of @Component:

@Component
public @interface Service {
}

Just like @Repository, @Service is also a type of @Component. That means Spring will also automatically detect such beans.

The @Service annotation represents that our bean holds some business logic. Till date, it doesn’t provide any specific behavior over @Component.

Still, we should annotate the service-layer beans with the @Service annotation to make our intent clear. Additionally, we never know if someday Spring chooses to add some specific functionality to it.

Differences in NutShell:

Let’s quickly sum up the differences between @Component, @Repository and, @Service:

@Component is the most generic stereotype and marks a bean as a Spring-managed component
Both @Service and @Repository annotations are the specializations over the @Component annotation
@Repository is a stereotype used for persistence layer. It translates any persistence related exceptions into a Spring’s DataAccessException
@Service is used for the beans at the service layer. Currently, it doesn’t offer any additional functionality over @Component
It’s always preferable to use @Repository and @Service annotations over @Component, wherever applicable. It communicates the bean’s intent more clearly

Conclusion:

In this mini-tutorial, we have learned the difference between the popular Spring annotations – @Component, @Service, and @Repository.

To conclude, we should always prefer using the annotations based on their specific layer conventions.

Published on Java Code Geeks with permission by Shubhra Srivastava, partner at our JCG program. See the original article here: @Component vs @Repository vs @Service in Spring

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