title: JPA readonly mapping
body: <p>Toplink can use read-only mappings when multiple attributes in an object map to the same fields in the database but only one of the mappings can write to the field.</p>
  <p>Does JPA has such feature, how to write annotation? I have one <code>@ManyToOne</code> and one <code>@Column</code> annotation which need to map to same field in database.</p>
  <pre class="lang-java prettyprint-override"><code>@ManyToOne(optional=false, fetch=FetchType.LAZY)
  @JoinColumn(name=&quot;USR_ID&quot;, referencedColumnName=&quot;USER_ID&quot;, nullable=false)
  private User user;
      
  /** @generated **/
  @Column(name=&quot;USER_ID&quot;, nullable=false, length=30)
  private String userId;
  </code></pre>