How to save child entity with Spring data JPA repositories if you know the parent Id?

For example if we have one to many relation:

@Entity
public class Customer {
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
    private String firstName;
    private String lastName;
    @ManyToOne
    private CustomerCategory category;
}

@Entity
public class CustomerCategory {
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;
    private String name;
}

One can do something like:

CustomerCategory someCategory = customerRepository.findOne(1L);// how to skip that line. The id should be enough. 
Customer cust = new Customer("Evgeni", "Dimitrov", someCategory);           
customerRepository.save(cust);

JPA can do load(just create a proxy and set the Id) instead of 'get'(select from the DB). Is that possible with Spring Data JPA?