How to map Iterable to its DTO?

I have the following repository:

PermissionRepository:

public interface PermissionRepository extends CrudRepository<Permission, Long>,
        SearchRepository<Permission> {

}

In my service, I am trying to map Permission entity to PermissionDTO, but as findAll() method returns Iterable<T> (Iterable<T> findAll();), I cannot convert as shown below as I generally use for List<T>. It throws “Cannot resolve method ‘stream’ in ‘Iterable’” error for the .stream() method.

List<PermissionDTO> list = permissionRepository.findAll()
        .stream()
        .map(PermissionDTO::new)
        .collect(Collectors.toList());

So, how can I map this Permission entity to PermissionDTO?

Answer

There are 3 ways to do what you want

Override findAll and make it return a List

public interface PermissionRepository extends CrudRepository<Permission, Long> {
    @Override
    List<Permission> findAll();
}

Implement JpaRepository instead of CrudRepository.

public interface PermissionRepository extends JpaRepository<Permission, Long>,
    SearchRepository<Permission>

Convert Iterable to Stream using StreamSupport.

StreamSupport.stream(iterable.spliterator(), false).map(PermissionDTO::new)
    .collect(Collectors.toList());