How to use findAll() on CrudRepository returning a List instead of Iterable [duplicate]

Question

I want to write a FindAll() method which returns a List of all Student objects. But the CRUDRepository only has Iterable<> findAll().

The goal is to get all students in a List and pass it to the API Controller so I can get all the students with a http GET.

What would be the best way to convert this method to List<> FindAll()

In my current code the findAll method in the StudentService gives me the Incompatible types found: Iterable. Required: List error.

Service

@Service
@RequiredArgsConstructor
public class StudentServiceImpl implements StudentService {

    @Autowired
    private final StudentRepository studentRepository;

    //Incompatible types found: Iterable. Required: List
    public List<Student> findAll() {
        return studentRepository.findAll();
    }
}

API Controller

@RestController
@RequestMapping("/api/v1/students")

public class StudentAPIController {

    private final StudentRepository studentRepository;

    public StudentAPIController(StudentRepository studentRepository) {
        this.studentRepository = studentRepository;
    }

    @GetMapping
    public ResponseEntity<List<Student>> findAll() {
        return ResponseEntity.ok(StudentServiceImpl.findAll());
    }
}

StudentRepository

public interface StudentRepository extends CrudRepository<Student, Long> {

}

Answer 1

You can simply define an abstract method List<Student> findAll() in the StudentRepository interface. Something simple like this:

public interface StudentRepository extends CrudRepository<Student, Long> {
    List<Student> findAll();
}