we can declare repository classes in this way
public interface DepartmentRepository extends JpaRepository<Department, Integer>
and this way
@Repository
public interface DepartmentRepository extends JpaRepository<Department, Integer>
What is the difference between this two approach mentioned. Because if we remove the @Repository annotation then the code will work fine then what is the difference, can anyone explain me on this.
While the other answers go into detail about the sterotype annotations they don't document why exactly its not needed, its a Spring Boot feature - not Spring Framework.
With Spring Boot, it will automatically scan child packages from the main SpringBootApplication class and detect repository interfaces and create beans for you with the use of Autoconfiguration that is part of the SpringBootApplication
Spring Data repositories usually extend from the Repository or CrudRepository interfaces. If you use auto-configuration, repositories are searched from the package containing your main configuration class (the one annotated with @EnableAutoConfiguration or @SpringBootApplication) down.
If you were not using Spring Boot, or the repository was not in package, or child-package, of the Spring Boot Application it would need to be annotated and the package scanned, or a bean created.
Spring Data can create implementations of @Repository interfaces of various flavors. Spring Boot handles all of that for you, as long as those @Repositories are included in the same package (or a sub-package) of your @EnableAutoConfiguration class.
For many applications, all you need is to put the right Spring Data dependencies on your classpath. There is a spring-boot-starter-data-jpa for JPA, spring-boot-starter-data-mongodb for Mongodb, etc. To get started, create some repository interfaces to handle your @Entity objects.
Spring Boot tries to guess the location of your @Repository definitions, based on the @EnableAutoConfiguration it finds. To get more control, use the @EnableJpaRepositories annotation (from Spring Data JPA).
See the documentation for more information on this behavior e.g. taking more control over the creation of repositories.
Taken from the spring documentation:
The @Repository annotation is a marker for any class that fulfills the role or stereotype of a repository (also known as Data Access Object or DAO). Among the uses of this marker is the automatic translation of exceptions, as described in Exception Translation.
It serves mainly as a stereotype marker, but @Repository is a specialization of @Component, which spring uses for classpath scanning.
https://www.journaldev.com/21460/spring-repository-annotation
@Repository annotation is used to indicate that the class provides the mechanism for storage, retrieval, search, update and delete operation on objects.
Spring Repository annotation is a specialization of @Component annotation, so Spring Repository classes are autodetected by spring framework through classpath scanning.
@Repository is used to create Bean. If you are not using this annotation then there can be some other way you are creating the bean, therefore, it does not make any difference for you.
@Repository is a special type of @Component and we annotate the interface which acts as a repository with @Repository annotation. @Repository deals with catching exceptions that are related to data persistence.
We don't need to use @Repository annotation when we are extending JpaRepository because Spring detects that the predefined JpaRepository has been extended and recognises the interface that extends JpaRepository as a repository.