Spring Data JPA Repository

Javarevisited

public interface UserRepository extends JpaRepository<User, Long> {
// User : JPA entity, Long : Primary Key type
	public User findByNickname(String nickname)
}

Spring Data JPA Magic

• All above XXXRepository are Interfaces
• By extending those, you inherit all the functions defined under those (CRUD operations, sorting, etc)
• You can use these functions without implementing the methods. How?
• When Spring application is launched, Spring Data JPA creates a proxy object which implements the custom interface.
• This proxy object intercepts method calls made to the interface's functions and analyzes the method name and parameters to determine what it will do
• Then it will dynamically generate the appropriate database query
• JPA provider (ex, Hiberante) will execute the dynamically generated query on the underlying database

 

Spring Data JPA Naming Conventions

Method	Description
save()	Save a record
delete()	Deletes a record
count()	Counts the number of records
findOne()	Find one record
findAll()	Find all records

Keyword	Example
And	findByNameAndEmail(String name, String email)
GreaterThan	findByAgeGreaterThan(int age)
IsNull	findByNameIsNull()

Can find more from https://docs.spring.io/spring-data/jpa/docs/1.10.1.RELEASE/reference/html/