public class Urls
{
   @Id
   @GeneratedValue( generator = "hibernate-uuid" )
   private String id;

   @Column( name = "url" )
   private String url;

   @OneToOne
   @PrimaryKeyJoinColumn
   private GzHtml gzHtml;

public class GzHtml
{
   @Id
   @Column( name = "url_id" )
   private String urlId;

   @Column( name = "html" )
   private byte[] html;

      Urls u = new Urls();
      u.setUrl( url.toString() );
      
      GzHtml h = new GzHtml();
      h.setHtml( Utility.compress( html ) );

      u.setGzHtml( h );
      session.save( u );

@OneToOne(cascade = CascadeType.ALL)
...