Erro em clicar no botão

To recebendo o seguinte erro qdo tento fazer uma busca em uma variável do tipo integer:

    [ServletException in:/views/software/cadSoftware_show.jsp] null' 

Meu action, está assim:

    public ActionForward pesquisar(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws WebActionException {
        try {
        	SoftwareBusinessDelegate softwareBusinessDelegate = (SoftwareBusinessDelegate) getBusinessDelegate();
            Serializable showSoft = (Serializable) softwareBusinessDelegate.findSoftwareById(((PersistentObjectGenerate)form).getPersistentObj());
            request.setAttribute(BasicAction.TABLE_DATA_ATTRIBUTE, showSoft);

        } catch (GpbrPersistException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return mapping.findForward("showCadSoftware");
    }

meu arquivo cadSoftware_show.jsp está assim:

  <TABLE border="0" cellpadding="0" cellspacing="0">
  	<TR>
  		<TD width="30%" nowrap>
  			 <FONT class='lbl1'><b>Código do Software:</b></FONT>
         <html:text onkeypress="onlyNum();" property="auxId" size="4" value="" maxlength="4" styleClass="frmTxt1"/>
  		</TD>
         <TD nowrap>  
        <html:button property="" value="consultar" styleClass="bto1" onclick="pesquisar(auxId.value, 'pesquisar');" />
      </TD>
  	</TR>
  </TABLE>
  <BR>
	<TABLE border="0"	cellpadding="0" cellspacing="0" width="100%">
		<TR>
			<TD nowrap>
				<gp:grid tableDataSuffix="" gridMetaData="gridSoftware" paginate="true" action="/cadSoftware.do" formName="softwareForm" />
			</TD>
		</TR>
  </TABLE>

e o grid esta assim:

body.attribute.1 = id
body.htmlAttributes.1 = class="txttab1" align="center" width="10%"
body.link.function.1 = pesquisar([id], 'showDetail');

body.attribute.2 = soft
body.htmlAttributes.2 = class="txttab1" align="center" width="40%"

body.attribute.3 = descricao
body.htmlAttributes.3 = class="txttab1" align="center" width="30%"

body.attribute.4 = versao
body.htmlAttributes.4 = class="txttab1" align="center" width="20%"

alguma idéia?