Botao so fica able qdo e uma coluna e selcionada!

Front-end
#1

tenho minha datatable por exemplo, como so abilitar qdo a linha for selecionada

 <p:dataTable id="tableUploads" var="upload" value="#{UploadBean.arquivosUp}"
                                                 paginator="true" rows="5"  rowKey="#{upload.idArquivo}"
                                                 selection="#{UploadBean.uploadSelecionado}" 
                                                 selectionMode="single"
                                                 paginatorTemplate="{CurrentPageReport}  {FirstPageLink} 
                                                 {PreviousPageLink}
                                                 {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}"
                                                 rowsPerPageTemplate="5,10">

                                       <p:column headerText="Compartilhar com" style="width:185px">
                                            <center>
                                               <p:commandButton value="Compartilhar" 
                                                             update=":compartilhar" disabled="true"
                                                             oncomplete="CompartilharAqruivo.show()">
                                                   <f:setPropertyActionListener 
                                                       target="#{UploadBean.uploadSelecionado}"
                                                           value="#{upload}"  />
                                               </p:commandButton>
                                            </center>
                                        </p:column>
#2