Spring Data JPA中findOne()和getOne()用法

/**   
 *    Retrieves an entity by its id.
 *    @param id must not be {@literal null}.
 *    @return the entity with the given id or {@literal null} if none found
 *    @throws IllegalArgumentException if {@code id} is {@literal null}
  * /

      T findOne(ID id);
/**
 *  Returns a reference to the entity with the given identifier.
 * 
 *  @param id must not be {@literal null}.
 *  @return a reference to the entity with the given identifier.
 *  @see EntityManager#getReference(Class, Object)
 */
  
    T getOne(ID id);

@NoRepositoryBean
public interface CrudRepository<T, ID extends Serializable> extends Repository<T, ID> {
    <S extends T> S save(S var1);

    <S extends T> Iterable<S> save(Iterable<S> var1);

    T findOne(ID var1);

    boolean exists(ID var1);

    Iterable<T> findAll();

    Iterable<T> findAll(Iterable<ID> var1);

    long count();

    void delete(ID var1);

    void delete(T var1);

    void delete(Iterable<? extends T> var1);

    void deleteAll();
}

@NoRepositoryBean
public interface CrudRepository<T, ID> extends Repository<T, ID> {
    <S extends T> S save(S var1);

    <S extends T> Iterable<S> saveAll(Iterable<S> var1);

    Optional<T> findById(ID var1);

    boolean existsById(ID var1);

    Iterable<T> findAll();

    Iterable<T> findAllById(Iterable<ID> var1);

    long count();

    void deleteById(ID var1);

    void delete(T var1);

    void deleteAll(Iterable<? extends T> var1);

    void deleteAll();
}