Spring data jpa. Partial custom repository implemantation - spring-data

Question

We can write custom implementation of repository:
interface UserRepositoryCustom {
public void someCustomMethod(User user);
}
class UserRepositoryImpl implements UserRepositoryCustom {
public void someCustomMethod(User user) {
// Your custom implementation
}
}
But what if I want customize only some methods? For example:
interface UserRepositoryCustom {
public User findByFirstName(String firstName);
#Query("select u.firstName from User u where u.age > 18")
public Set<String> findAllAdultUsers();
public void someCustomMethod(User user);
}
class UserRepositoryImpl implements UserRepositoryCustom {
//I want implement only this method
public void someCustomMethod(User user) {
// Your custom implementation
}
}
If I declare a class, which implements an interface, I have to implement all methods, but I want to write custom logic for only one method.
Is it possible to do this? Maybe I can make this class abstract? Will spring data resolve this?

Answer 1

I think only solution is to split methods in 2 interfaces: first - for spring query method, and second - for custom implementation, as shows in doc: http://docs.spring.io/spring-data/data-jpa/docs/current/reference/html/#repositories.single-repository-behaviour.
But I think solution with abstract class would be more natural and logic: you provide only needed method implementations and spring data do the rest for you.

Answer 2

Let's say you have a repository with a few methods whose implementations are generated by Spring:
interface UserRepository extends CrudRepository<User,String> {
List<User> findUserByLastname(String lastName);
}
In order to add a method with a custom implementation, you need to create another interface that only contains the methods you want to customize, and make your repository extend the custom one:
interface CustomUserRepository {
User someCustomMethod();
}
interface UserRepository extends CrudRepository<User,String>, CustomUserRepository {
List<User> findUserByLastname(String lastName);
}
You can then implement the extra methods by creating an implementation class for the new interface:
class CustomUserRepositoryImpl implements CustomUserRespository {
#Override
User someCustomMethod() {
// implementation goes here.
}
}
The class name is important here: in order for Spring to find it, it should be the name of the interface that is being extended with Impl on the end.
The implementation repository is a normal Spring bean, so you can autowire a constructor to inject various dependencies.
There is a much more detailed tutorial here: https://www.baeldung.com/spring-data-composable-repositories.