Hi, I'm trying to create a compost primary key and this error happens:

SEVERE: Invoking method failed: xdoclet.modules.hibernate.HibernateTagsHandler.ifHasCompositeId, line=169 of template file
...
Caused by: java.lang.NullPointerException

My code:


public class AcessoId implements Serializable{

// <editor-fold defaultstate="collapsed" desc=" Property: String id_usuario ">
private String id_usuario;
/**
* @hibernate.property
* column="id_usuario"
* @hibernate.column
* name="id_usuario"
*/
public String getId_usuario() {
return id_usuario;
}
public void setId_usuario(String id_usuario) {
this.id_usuario = id_usuario;
}
// </editor-fold>

// <editor-fold defaultstate="collapsed" desc=" Property: String cod_sist ">
private String cod_sist;
/**
* @hibernate.property
* column="cod_sist"
* @hibernate.column
* name="cod_sist"
*/
public String getCod_sist() {
return cod_sist;
}
public void setCod_sist(String cod_sist) {
this.cod_sist = cod_sist;
}
// </editor-fold>
}


package custom.entities ;
/**
*
*
* @hibernate.class
* table="acesso"
*
*/
public class Acesso {

// <editor-fold defaultstate="collapsed" desc=" PrimaryKey: custom.entities.AcessoId acessoId ">
private custom.entities.AcessoId acessoId;
/**
* @hibernate.id
* generator-class="assigned"
*/
public custom.entities.AcessoId getAcessoId () {
return acessoId;
}
public void setAcessoId (custom.entities.AcessoId acessoId) {
this.acessoId = acessoId;
}
//</editor-fold>


}
What's happen?

Thank's