@Component, @Service, @Repository, @Controller in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @Component annotation in Spring Boot?

<p><code>@Component</code> marks a class as a Spring-managed bean. It tells Spring to create an instance of this class and manage its lifecycle automatically.</p>

beginner

How does @Service differ from @Component?

<p><code>@Service</code> is a specialized form of <code>@Component</code> used to mark service layer classes. It helps clarify the role of the class as holding business logic.</p>

intermediate

What role does @Repository play in a Spring Boot application?

<p><code>@Repository</code> marks a class as a data access object (DAO). It also enables Spring to translate database exceptions into Spring’s data access exceptions.</p>

beginner

What is the main use of @Controller in Spring Boot?

<p><code>@Controller</code> marks a class as a web controller that handles HTTP requests and returns views or data responses.</p>

intermediate

Can a class be annotated with more than one of these annotations: <code>@Component</code>, <code>@Service</code>, <code>@Repository</code>, <code>@Controller</code>?

<p>No, these annotations are specialized stereotypes of <code>@Component</code>. You use one that best fits the class role to keep your code clear and organized.</p>

Which annotation would you use to mark a class that handles business logic in Spring Boot?

A @Component

B @Controller

C @Repository

D @Service

@Service is used for classes that contain business logic.

What does the @Repository annotation help with besides marking a class as a data access object?

A Managing service layer logic

B Handling HTTP requests

C Translating database exceptions into Spring exceptions

D Creating REST endpoints

@Repository enables exception translation for database errors.

Which annotation is the most general stereotype for Spring-managed beans?

A @Component

B @Service

C @Controller

D @Repository

@Component is the general-purpose stereotype annotation.

If you want to create a class that handles web requests and returns views, which annotation should you use?

A @Repository

B @Controller

C @Service

D @Component

@Controller is used for web controllers handling HTTP requests.

Is it good practice to annotate a class with both @Service and @Repository?

A No, use one annotation that fits the class role

B Yes, to combine business and data logic

C Yes, to improve performance

D No, because Spring does not allow multiple annotations

Use one stereotype annotation per class to keep roles clear.

Explain the difference between @Component, @Service, @Repository, and @Controller in Spring Boot.

Think about the role each annotation plays in the app layers.

Why is it important to use the correct stereotype annotation for a class in Spring Boot?

Consider how Spring and other developers understand your code.