Why isn't my bean being populated?

[SuperMoonster]

Hello everyone, I'd like your help to find an error. I have an action, a form bean, but it isn't being populated! Could you help my find out why? There goes my code:

struts-config:

      <form-bean name="addDelUpdMPFichaTecnicaForm" type="auge.form.AddDelUpdMPFichaTecnicaForm"/> 

        <action
                path="/AddMPFichaList"
                type="auge.action.AddMPFichaListAction"
                name="addDelUpdMPFichaTecnicaForm" 
                scope="session" 
                parameter="action"
                validate="true"
                input="/pages/fichaTecnica/fichaTecnica.jsp"> 
                <forward name="success"  path="/pages/fichaTecnica/fichaTecnica.jsp"/>          
                <forward name="error"  path="/pages/erro.jsp"/>          
        </action>

In my action, I do:

            mpFichaTecnica.setMateriaPrima(MateriaPrimaService.getInstance().getMateriaPrima(addMpFichaTecnicaForm.getMateriaPrima()));            mpFichaTecnica.setQuantidade(addMpFichaTecnicaForm.getQuantidade());            mpFichaTecnica.setPrincipal(addMpFichaTecnicaForm.getPrincipal());

In my jsp, I have:

   <html:form action="/AddMPFichaList" method="post" focus="materiaPrima">    
   <table border="0" align="center" width="100%">
   <tr>
       <td>Matéria Prima</td>         
       <td>Quantidade</td>              
       <td>Principal</td>                     
       <td></td>                     
   </tr>
   <tr>
       <td> <html:text property="materiaPrima" size="5" onchange="javascript:limpaMateria()"/> 
                            <img src="/AugeProducao/config/lupa.gif" alt="Clique aqui para visualizar as opções" height="20" width="20" onclick="javascript:abreJanelaMateria()"></img>
                            <input type="text" name="nme_materia" size="55" readonly="true"></td> 
       <td> <html:text property="quantidade" size="5" /> </td>
       <td> <html:text property="principal" size="5" /> </td>
       <td> <html:link action="/AddMPFichaList.do">Adicionar</html:link></td>
   </tr>
   </table>
   </html:form>

I activate the action from the link.

In my action, when I try to get the values from the form, everything comes blank, like if I hadn't informed anything.

Anyone has a clue? thanks