Can not Populate the form on combo box change

I am using Spring Webflow and Richfaces,

This is my Inventory.xml for flow.

<view-state id="inventory">
        <on-render>
            <evaluate expression="inventoryService.getUsageType()" result="flowScope.usage"  />
            <evaluate expression="inventoryService.unitSelectItems()" result="flowScope.unitListForCombo"  />
            <evaluate expression="inventoryService.getCompanyById()" result="flowScope.companyListForCombo" />
            <evaluate expression="inventoryService.productSelectItems()" result="flowScope.productListForCombo" />
        </on-render>        
        <transition on="add">
            <evaluate expression="inventoryService.addProduct(product,company)"/>
        </transition>
        <transition on="submit">
            <evaluate expression="inventoryService.saveCompanyDetails(company)"/>
        </transition>
        <transition on="populateProductDetails">
            <evaluate expression="inventoryService.populateProductDetails(product)" result="flowScope.product" result-type="com.webaccess.cms.domain.Product"/>
        </transition>

i want to fill up form with the data according to dropdown value,

here is my page where i am changing dropdown using,

now i am concerned with product population in this case here is my inventory.xhtml page,

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<ui:composition xmlns="http://www.w3.org/1999/xhtml"
                xmlns:ui="http://java.sun.com/jsf/facelets"
                xmlns:h="http://java.sun.com/jsf/html"
                xmlns:f="http://java.sun.com/jsf/core"
                xmlns:sf="http://www.springframework.org/tags/faces"
                xmlns:a4j="http://richfaces.org/a4j"
                xmlns:rich="http://richfaces.org/rich"
                xmlns:c="http://java.sun.com/jsp/jstl/core"
                template="/WEB-INF/templates/template.xhtml">
    <ui:define name="topPanel">
        <ui:include src="/WEB-INF/include/includeTop.xhtml" />
    </ui:define>
    <ui:define name="middlePanel">
        <ui:include src="/WEB-INF/include/includeMidPanelInventry.xhtml" />
    </ui:define>
    <ui:define name="leftPanel">
        <ui:include src="/WEB-INF/include/includeInventory.xhtml" />
    </ui:define>

<ui:define  name="content">
        <table width="100%" border="0" cellpadding="0" cellspacing="1" bordercolor="#e1dfe0" bgcolor="#e1dfe0">
            <tr>
                <td bgcolor="#dae1e5">
                    <table width="100%" border="0" cellspacing="0" cellpadding="0">
                        <tr>
                            <td height="35" bgcolor="#DAE1E5">
                                <h:form id="frmInventory">
                                    <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                        <tr>
                                            <td width="10"><rich:spacer width="10" height="10" /></td>
                                            <td>
                                                <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                    <tr>
                                                        <td height="35" class="headline"><h:outputText id="lblCompanyInfo" value="#{messages.inv_company_info}" /></td>
                                                    </tr>
                                                </table>
                                            </td>
                                            <td width="10"><rich:spacer width="10" height="10" /></td>
                                        </tr>
                                        <tr>
                                            <td> </td>
                                            <td bgcolor="#DAE1E5">
                                                <table width="100%" border="0" cellpadding="0" cellspacing="0">
                                                    <tr>
                                                        <td bgcolor="#DAE1E5">
                                                            <table width="100%" border="0" cellspacing="0" cellpadding="6">
                                                                <tr>
                                                                    <td width="181" align="left" valign="top" class="dt-time"><h:outputText id="lblCompanyName" value="#{messages.inv_company_name}" /></td>
                                                                    <td width="253" valign="top">
                                                                        <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                                            <tr>
                                                                                <th id="cmbCompName" width="54%" align="left" scope="col">
                                                                                    <rich:comboBox id="cmbCompanyName" value="#{company.companyId}"  inputClass="client-dro" enableManualInput="false"   defaultLabel="Select" width="130px">
                                                                                        <f:selectItems value="#{companyListForCombo}" />
                                                                                        
                                                                                    </rich:comboBox>                                                                                    
                                                                                </th>
                                                                                <th id="txtCompName" width="54%" align="left" scope="col" style="display:none">
                                                                                    <h:inputText id="txtCompanyName" value="#{company.companyName}" style="width:130px" size="10" maxlength="10" styleClass="telephone"/>
                                                                                </th>
                                                                                <td width="4%" scope="col"><span class="dt-time"><rich:spacer width="5" height="1"/></span></td>
                                                                                <td width="42%" align="left" scope="col"> <a4j:commandButton id="btnNew" onclick="changeValue();"  styleClass="button-css" value="#{messages.btn_new}" ></a4j:commandButton></td>
                                                                            </tr>
                                                                        </table>
                                                                    </td>
                                                                    <td width="2" valign="top" class="dt-time"><rich:spacer width="5" height="1" /></td>
                                                                    <td width="55" valign="top" class="dt-time"><h:outputText id="lblContact" value="#{messages.inv_contact}" /></td>
                                                                    <td width="132" valign="top" class="dt-time"><h:inputText id="txtContact" value="#{company.contactNo}" style="width:130px" styleClass="telephone"/></td>
                                                                    <td width="320" rowspan="3" valign="top"> </td>
                                                                </tr>
                                                                <tr>
                                                                    <td align="left" valign="top" class="dt-time"><h:outputText id="lblAddress" value="#{messages.inv_address}" /></td>
                                                                    <td colspan="4">
                                                                        <h:inputTextarea id="txtAddress" value="#{company.address}" styleClass="disc" rows="3" cols="45"/>
                                                                    </td>
                                                                </tr>
                                                                <tr>
                                                                    <td align="left" valign="top" class="dt-time"> </td>
                                                                    <td colspan="4">
                                                                        <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                                            <tr>
                                                                                <th scope="col"><table width="100%" border="0" cellspacing="2" cellpadding="0">
                                                                                        <tr>
                                                                                            <td align="left" class="table-head" ><h:outputText id="lblCity" value="#{messages.inv_city}" /></td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td>
                                                                                                <span class="table-head">
                                                                                                    <h:inputText id="txtCity" value="#{company.city}" style="width:130px" size="10" maxlength="10" styleClass="telephone"/>
                                                                                                </span>
                                                                                            </td>
                                                                                        </tr>
                                                                                    </table>
                                                                                </th>
                                                                                <th scope="col"> </th>
                                                                                <th scope="col">
                                                                                    <table width="100%" border="0" cellspacing="2" cellpadding="0">
                                                                                        <tr>
                                                                                            <td align="left" class="table-head" ><h:outputText id="lblState" value="#{messages.inv_state}" /></td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td>
                                                                                                <span class="table-head">
                                                                                                    <h:inputText id="txtState" value="#{company.state}" style="width:130px" styleClass="telephone"/>
                                                                                                </span>
                                                                                            </td>
                                                                                        </tr>
                                                                                    </table>
                                                                                </th>
                                                                                <th scope="col"> </th>
                                                                                <th scope="col">
                                                                                    <table width="100%" border="0" cellspacing="2" cellpadding="0">
                                                                                        <tr>
                                                                                            <td align="left" class="table-head" ><h:outputText id="lblSuburban" value="#{messages.inv_country}" /></td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td>
                                                                                                <span class="table-head">
                                                                                                    <h:inputText id="txtCountry" value="#{company.country}" style="width:130px" styleClass="telephone"/>
                                                                                                </span>
                                                                                            </td>
                                                                                        </tr>
                                                                                    </table>
                                                                                </th>
                                                                                <th scope="col"> </th>
                                                                                <th scope="col">
                                                                                    <table width="100%" border="0" cellspacing="2" cellpadding="0">
                                                                                        <tr>
                                                                                            <td align="left" class="table-head" ><h:outputText id="lblPincode" value="#{messages.inv_pincode}" /></td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td>
                                                                                                <span class="table-head">
                                                                                                    <h:inputText id="txtPincode" value="#{company.pinCode}" style="width:130px" maxlength="6" styleClass="telephone"/>
                                                                                                </span>
                                                                                            </td>
                                                                                        </tr>
                                                                                    </table>
                                                                                </th>
                                                                            </tr>
                                                                        </table>
                                                                    </td>
                                                                </tr>
                                                                <tr>
                                                                    <td align="left" valign="top" class="dt-time"><h:outputText id="lblAddress" value="#{messages.inv_website}" /></td>
                                                                    <td colspan="3">
                                                                        <h:inputText id="txtWebsite" value="#{company.webSite}" style="width:130px" styleClass="telephone"/>
                                                                    </td>
                                                                    <td>
                                                                        <h:commandButton id="btnSaveCompany" value="#{messages.btn_save}" styleClass="button-css" action="submit"/>
                                                                    </td>
                                                                </tr>
                                                            </table>
                                                        </td>
                                                    </tr>
                                                    <tr>
                                                        <td valign="top" bgcolor="#FFFFFF">
                                                            <table width="100%" border="0" cellpadding="2" cellspacing="5" bgcolor="#DAE1E5">
                                                                <tr>
                                                                    <td width="788"><span class="dt-time"><h:outputText id="lblProductInfo" value="#{messages.inv_product_info}" /></span></td>
                                                                    <td width="263"></td>
                                                                </tr>
                                                                <tr>
                                                                    <td valign="top">
                                                                        <table width="100%" border="0" cellpadding="0" cellspacing="1" bgcolor="#cad1d2">
                                                                            <tr>
                                                                                <td scope="col">
                                                                                    <table width="100%" border="0" cellpadding="6" cellspacing="0" bgcolor="#F3F7F8">
                                                                                        <tr>
                                                                                            <td colspan="6" valign="top" bgcolor="#F3F7F8" class="dt-time"><rich:spacer width="1" height="2" /></td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <!--td colspan="6" valign="top" bgcolor="#F3F7F8" class="dt-time">
                                                                                                <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                                                                    <tr>
                                                                                                        <td width="8" align="left" valign="top" scope="col"><rich:spacer width="4" height="5" /></td>
                                                                                                        <td width="44" align="left" valign="top" scope="col"><h:outputText id="lblProduct" value="#{messages.inv_product}" /></td>
                                                                                                        <td width="10" align="left" valign="middle" scope="col"><rich:spacer width="10" height="1" /></td>
                                                                                                        <td width="191" align="left" valign="top" scope="col">
                                                                                                            <rich:comboBox id="cmbProduct" inputClass="client-drop" enableManualInput="false" defaultLabel="Select" width="130px">

<a4j:support action="populateProductDetails" event="onchange" reRender="txtCompName"  />
                                                                                                            </rich:comboBox>
                                                                                                            <h:inputText id="txtProduct" value="#{product.prd_name}" style="width:130px" maxlength="6" styleClass="mat-in"/>
                                                                                                        </td>
                                                                                                        <td width="10" scope="col"><rich:spacer width="10" height="1" /></td>
                                                                                                        <td width="465" align="left" scope="col"><h:inputTextarea  id="taProductDescription" rows="3" styleClass="disc" value="#{product.prd_description}" cols="45"/></td>
                                                                                                    </tr>
                                                                                                </table>
                                                                                            </td-->
                                                                                            <td colspan="4" width="253" valign="top">
                                                                                                <table width="100%" border="0" cellspacing="0" cellpadding="0">
                                                                                                    <tr>
                                                                                                        <td width="44" align="left" valign="top" scope="col"><h:outputText id="lblProduct" value="#{messages.inv_product}" /></td>
                                                                                                        <td width="10" align="left" valign="middle" scope="col"><rich:spacer width="10" height="1" /></td>
                                                                                                        <th id="cmbProdName" width="54%" align="left" scope="col">
                                                                                                            <rich:comboBox id="cmbProductName" value="#{product.prd_id}"  inputClass="client-dro" enableManualInput="false"   defaultLabel="Select" width="130px">
                                                                                                                <f:selectItems value="#{productListForCombo}" />
                                                                                                                <a4j:support action="populateProductDetails"  event="onchange" reRender="txtProdName"  />
                                                                                                            </rich:comboBox>
                                                                                                        </th>
                                                                                                        <th id="txtProdName" width="54%" align="left" scope="col" style="display:none">
                                                                                                            <h:inputText id="txtProductName" value="#{product.prd_name}"  style="width:130px" size="10" maxlength="10" styleClass="telephone"/>
                                                                                                        </th>
                                                                                                        <td width="4%" scope="col"><span class="dt-time"><rich:spacer width="5" height="1"/></span></td>
                                                                                                        <td width="42%" align="left" scope="col"> <a4j:commandButton id="btnNewProd" onclick="changeValue();"  styleClass="button-css" value="#{messages.btn_new}" ></a4j:commandButton></td>
                                                                                                        <td width="10" scope="col"><rich:spacer width="10" height="1" /></td>
                                                                                                        <td colspan="3" width="465" align="left" scope="col"><h:inputTextarea  id="taProductDescription" rows="3" styleClass="disc" value="#{product.prd_description}" cols="45"/></td>
                                                                                                    </tr>
                                                                                                </table>
                                                                                            </td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            
                                                                                            <td  width="50" rowspan="4"><rich:spacer width="50" height="1" /></td>
                                                                                            <td colspan="2"  width="153" align="left" class="dt-time"><h:outputText id="lblSellingPrice" value="#{messages.inv_sellPrice}" /></td>
                                                                                            <td colspan="2" width="236" align="left">
                                                                                                
                                                                                                <h:inputText id="txtSellingelPrice" value="#{product.prd_selling_price}" style="width:130px" maxlength="6" styleClass="mat-in"/>
                                                                                            </td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td align="left" class="dt-time"> </td>
                                                                                            <td align="left" class="dt-time"><h:outputText id="lblQuantity" value="#{messages.inv_qty}" /></td>
                                                                                            <td align="left">
                                                                                                <h:inputText id="txtQuantity" value="#{product.prd_qty}" style="width:130px" maxlength="6" styleClass="mat-in"/>
                                                                                                <rich:comboBox id="cmbQuantity" value="#{product.prd_unit_id}" inputClass="client-drop" enableManualInput="false" defaultLabel="Select" width="130px">
                                                                                                    <f:selectItems value="#{unitListForCombo}" />
                                                                                                </rich:comboBox>

</td>
                                                                                            <td align="left" class="dt-time"><h:outputText id="lblPurchasePrice" value="#{messages.inv_purchasePrice}" /></td>
                                                                                            <td align="left">
                                                                                                
                                                                                                <h:inputText id="txtPurchasePrice" value="#{product.prd_cost_price}" style="width:130px" maxlength="6" styleClass="mat-in"/>
                                                                                            </td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td align="left" class="dt-time"> </td>
                                                                                            <td align="left" class="dt-time"><h:outputText id="lblReorderAlert" value="#{messages.inv_reorderAlert}" /></td>
                                                                                            <td align="left">
                                                                                                
                                                                                                <h:inputText id="txtReorderAlert" value="#{product.prd_alert_qty_shortage}"  style="width:130px" maxlength="6" styleClass="mat-in"/>
                                                                                            </td>
                                                                                            <td align="left" class="dt-time"><h:outputText id="lblTax" value="#{messages.inv_tax}" /></td>
                                                                                            <td align="left">
                                                                                                
                                                                                                <h:inputText id="txtTax" style="width:130px" value="#{product.prd_tax}"  maxlength="6" styleClass="mat-in"/>
                                                                                            </td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td align="left" class="dt-time"> </td>
                                                                                            <td align="left" class="dt-time"><h:outputText id="lblUsageType" value="#{messages.inv_usageType}" /></td>
                                                                                            <td align="left">
                                                                                                <rich:comboBox id="cmbUsageType" value="#{product.prd_usage_type_id}"  inputClass="client-drop" enableManualInput="false" defaultLabel="Select" width="130px">
                                                                                                    <f:selectItems value="#{usage}"/>
                                                                                                </rich:comboBox>

</td>
                                                                                            <td align="left"> </td>
                                                                                            <td> </td>
                                                                                        </tr>
                                                                                        <tr>
                                                                                            <td align="left" class="dt-time"><rich:spacer width="1" height="5" /></td>
                                                                                            <td align="left" class="dt-time"></td>
                                                                                            <td align="left"></td>
                                                                                            <td></td>
                                                                                            <td align="left"></td>
                                                                                            <td></td>
                                                                                        </tr>
                                                                                    </table>
                                                                                </td>
                                                                            </tr>
                                                                        </table>
                                                                    </td>
                                                                    <td></td>
                                                                </tr>
                                                                <tr>
                                                                    <td colspan="2" align="right">
                                                                        <table width="100%" border="0" cellpadding="10" cellspacing="5" bgcolor="#DAE1E5">
                                                                            <tr>
                                                                                <td width="161" valign="top"><h:commandButton id="btnAddCompany" value="#{messages.btn_add_company}" styleClass="button-comp" action="proceed"></h:commandButton></td>
                                                                                <td width="600"> </td>
                                                                                <td width="47" align="right"><h:commandButton id="btnSave" value="#{messages.btn_save}" styleClass="button-css" ></h:commandButton></td>
                                                                                <td width="542" align="left"><h:commandButton id="btnAddProduct" value="#{messages.btn_add_product}" styleClass="button-avb" action="add"></h:commandButton></td>
                                                                            </tr>
                                                                        </table>
                                                                    </td>
                                                                </tr>
                                                            </table>
                                                        </td>
                                                    </tr>
                                                </table>
                                            </td>
                                            <td> </td>
                                        </tr>
                                        <tr>
                                            <td height="50" colspan="3"><rich:spacer width="10" height="10" /></td>
                                        </tr>
                                    </table>
                                </h:form>
                            </td>
                        </tr>
                    </table>
                </td>
            </tr>
        </table>
    </ui:define>
</ui:composition>

and the service is as,

i can get return the product bean according to productId,

Now the problem is i can not see values populating in my form even though the bean is returned successfully.

what should i do to populate the form?
please help.

You are rendering txtProdName when the method is finished. You should be rerendering the complete form instead.

thank you sir,
i have understood the problem and works fine.
have a nice day.