What's the difference between @Component, @Repository & @Service annotations in Spring?

In Spring, the @Component annotation is used to mark a Java class as a candidate for component scanning. The @Repository annotation is a specialization of @Component for use in the persistence layer. The @Service annotation is also a specialization of @Component for use in the service layer.

These annotations are used to mark beans as candidates for auto-detection when using Spring's component-scanning feature. By default, the Spring Framework will scan the classpath for annotated components, and register them as beans in the application context.

Here are the main differences between these annotations:

• @Component: Can be used to mark any class as a candidate for component scanning.
• @Repository: Indicates that an annotated class is a repository, which is a mechanism for encapsulating storage, retrieval, and search behavior which emulates a collection of objects.
• @Service: Indicates that an annotated class is a service, which is a business logic processing that typically operates on the domain model to provide and manipulate data.

In practice, these annotations can be used interchangeably, and it is common to see all three used in a single application. However, it is generally a good idea to use the most specific annotation for a given class, to make the intent of the code more clear.

I hope this helps! Let me know if you have any questions.