Hi,

I have added like below for displaing errors in the oncomplete of upload file ,

<rich:fileUpload   fileUploadListener="#{uploadFileBean.fileUploadListener}"

                                 maxFilesQuantity="1" 

                                id="upload" addControlLabel="Browse...." clearAllControlLabel="Clear all"

                                clearControlLabel="Clear" stopEntryControlLabel="Stop process" doneLabel="Success" autoclear="false"                

                                 acceptedTypes="xls,xlsx"  

                                immediateUpload="#{uploadFileBean.autoUpload}"

                                 allowFlash="false" >

                                 <a4j:support event="onuploadcomplete" focus="upload"

                               reRender="info,uploadinfoSuccess,uploadinfoSuccessAll,uploadinfoBoth,uploadinfoFailure,uploadinfoFailureNodata,blacklistProfileDataScroll,blacklistData"

                                oncomplete="#{rich:component('addBlacklistUploadModal')}.show();"

                                onbeforedomupdate="#{rich:component('addBlacklistUploadModal')}.show();"/>                                                                   

                             </rich:fileUpload>   

                                <h:panelGrid columns="1" border="0"    >

                <h:panelGroup id="info">

                <rich:panel bodyClass="info">

                    <f:facet name="header">

                        <h:outputText value="Uploaded Files Info" />

                    </f:facet>

                    <h:outputText value="No files currently uploaded"

                        rendered="#{uploadFileBean.size==0}" />

                    <rich:dataGrid columns="1" value="#{uploadFileBean.files}" var="file" rowKeyVar="row">

                        <rich:panel bodyClass="rich-laguna-panel-no-header">

                            <h:panelGrid columns="2">                              

                                <h:panelGrid columns="2">

                                    <h:outputText value="File Name:" styleClass="celcomBlack01" />

                                    <h:outputText value="#{file.name}" styleClass="celcomBlack01" />

                                    <h:outputText value="File Length(bytes):" styleClass="celcomBlack01" />

                                    <h:outputText value="#{file.length}" styleClass="celcomBlack01" />

                                    <h:outputText value="File Type:" styleClass="celcomBlack01" />

                                    <h:outputText value="#{file.mime}" styleClass="celcomBlack01" />

                                </h:panelGrid>

                            </h:panelGrid>

                        </rich:panel>

                    </rich:dataGrid>

                </rich:panel>

                <rich:spacer height="3"/>

                <br />

                <a4j:commandButton action="#{uploadFileBean.clearUploadData}"

                    reRender="info, upload" value="Clear Uploaded Data"

                    rendered="#{uploadFileBean.size>0}" />

            </h:panelGroup>

            </h:panelGrid>     

<a4j:outputPanel ajaxRendered="true">

                <h:panelGrid id="uploadinfoSuccess" columns="5" border="0"  rendered="#{uploadFileBean.forSuccess =='Success'}">

                        <h:outputText id="fileupMessage" value="File Uploaded Successfully." styleClass="fieldError"/>

                </h:panelGrid>

Likewise manually u can add the output text for the displaying error in the screen.

Thanks,

Siva