检查数据表的素数是否为空

Question

I have a datatable in primefaces with jsf and I need to check when the datatable is empty with jquery/js, but I have just found tags for "normal" datatables that don't work on PF.

Bean

private ArrayList<Curso> curs = null;
private ArrayList<Curso> listado_filtrado;
private DefaultStreamedContent informe_cursos;

Html

 <p:outputPanel id="opTabla" > <p:dataTable id="tabla_elements" value="#{Cursos.curs}" var="element" filteredValue="#{Cursos.listado_filtrado}" emptyMessage="No se encontraron elementos" paginator="true" rows="20" currentPageReportTemplate="{startRecord} a {endRecord} de {totalRecords}" paginatorTemplate="{FirstPageLink} {PreviousPageLink} {CurrentPageReport} {NextPageLink} {LastPageLink}" paginatorPosition="bottom"> <p:ajax event="filter" update="exportar"/> <f:facet name="header"> <div class="header-field-col"> <p:commandButton id="anadir_curso" value="Añadir curso nuevo" icon="ui-icon-plus" /> </div> <div class="header-field-col"> <p:commandButton id="exportar" value="Exportar" ajax="false" disabled="#{empty Cursos.curs}" icon="ui-icon-arrowreturnthick-1-s"> <p:fileDownload value="#{Cursos.informeCursos}" /> </p:commandButton> </div> </f:facet> 

Answer 1

Your p:dataTable most likely references a list. Add an ajax event handler to it for eg the filter (all the ones that can make a page empty)

<p:dataTable value="#{myBean.myList}"...>
    <p:ajax event="filter" update="exportButton" ... >
    ...
</p:dataTable>

use a p:commandButton with a disabled attribute like this:

<p:commandButton id="exportButton" value="export" disabled="#{empty myBean.myList}" ... />

It disables the commandButton client and serverside if the list is empty. So users cannot hack it client-side either.

The 'update' element in the commandButton makes sure the button state is, well,... updated on the relevant events. This is all rather basic ajax stuff, maybe read some tutorial on that