如何将传递参数放入<p：confirm message =“”>？

Question

这就是我所拥有的：

   <p:growl id="message" showDetail="true" />

 <p:commandButton value="delete user" actionListener="#{bean.deleteUser(user)}"  update="@form"> 
 <p:confirm header="Confirm" message="Are you sure to delete #{user.username}?" icon="ui-icon-alert" />
   </p:commandButton>

   <p:confirmDialog global="true" showEffect="fade" hideEffect="fade">
      <p:commandButton value="yes" type="button" styleClass="ui-confirmdialog-yes" icon="ui-icon-check"  />
    <p:commandButton value="No" type="button" styleClass="ui-confirmdialog-no" icon="ui-icon-close" />
       </p:confirmDialog>

变量#{user.username}根本不会显示。 我做错了什么？