title: Update of of Composite Entity fails
body: <p>I have Person entity which has composition with Location Entity</p>
  
  <pre><code>@ManyToOne(fetch = FetchType.EAGER, cascade =
  { CascadeType.PERSIST, CascadeType.MERGE })
  @Cascade(
  {org.hibernate.annotations.CascadeType.SAVE_UPDATE })
  public Location getLocation()
  {
      return location;
  }
  </code></pre>
  
  <p>And Location Entity has Name as Id</p>
  
  <pre><code>@Id
  public String getName()
  {
      return name;
  }
  </code></pre>
  
  <p>I am getting following Exception when Person's location is changed from L1 to L2 in Spring MVC form where this Person entity is modelAttribute for the form.</p>
  
  <blockquote>
    <p>org.springframework.orm.hibernate3.HibernateSystemException:identifier of an instance of com.x.y.z.Location was altered from L2 to L1; nested exception is org.hibernate.HibernateException: identifier of an instance of com.x.y.z.Location was altered from L2 to L1</p>
  </blockquote>