jsf - Primefaces, dataexporter and watermark -

i have datatable filtered columns , using watermark set input value , save space in header, when try use dataexport pdf file rendered kind of reference watermark, like:

column title

---

org.primefaces.component.watermark.watermark@46339a4c
desired column content (...)

and structure of xhtml basically:

    <h:form id="formid">      <p:commandbutton value="export"ajax="false">         <p:dataexporter type="pdf" filename="file" preprocessor="#{my.stuff}" target="tableid" />     </p:commandbutton>      <p:datatable id="tableid" value="#{my.content}" var="mytable">         <p:column id="columnid1" filterby="#{mytable.item}">             <p:watermark value="item" forelement="formid:tableid:columnid1" />             <p:outputtext value=#{mytable.item}" />         </p:column>     </p:datatable>  </h:form> 

thanks in advance , sorry bad english.