title: Spring Data JPA save child without fetch the parent
body: <p>How to save child entity with Spring data JPA repositories if you know the parent Id?</p>
  
  <p>For example if we have one to many relation:</p>
  
  <pre><code>@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;
  }
  </code></pre>
  
  <p>One can do something like:</p>
  
  <pre><code>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);
  </code></pre>
  
  <p>JPA can do <code>load</code>(just create a proxy and set the Id) instead of 'get'(select from the DB). Is that possible with Spring Data JPA? </p>