use of abstract classes in sqlMap

[Guido García Bernardo]

Imagine the following abstract class: public abstract class Relationship {     private String dateRelation;     private Integer idUser;     // getters & setters } That allows to define several kinds of relations, i.e: public class Friendship extends Relationship {     private String comment;     // getters & setters } The SQL map:     <sqlMap>         <typeAlias alias="relation" type="my.package.Relationship" />         <insert id="insertFriend" parameterClass="relation">             insert into FRIENDS ( id_user, date_relation, comment )             values ( #idUser#, #dateRelation#, #comment# )         </insert>     </sqlMap> And my ibatis code throws a message error "There is not readable property 'comment' in my.package.Relationship".     Relationship friend = new Friendship( ... );     saveRelation( friend );     ...     public void saveRelation(Relationship relation) throws DAOException {         try {             if (relation instanceof Friendship) {                      getSqlMapExecutor().insert( "insertFriend", relation );             } else if ...             ...         } catch (SQLException e) {             throw new DAOException( "Error saving friend", e );         }     } Why ibatis does not discover object properties at runtime? Is there any way to use abstract classes in my sql-map files? I am not sure if I have explained my problem properly... Thank you very much. Guido García Bernardo