Threads in Java web app

[fayevalentine]

Hello again,

I am having trouble with a functionality in my java web application using PrimeFaces, I hope someone can guide me.

I launch a query in an Oracle database when I click a button (this query can last a little based in a date range the user selects)
so I have more or less this code:

ReportTh et  //This is my class extends Thread, where I write my report
public void genReport()
{
  //Here I connect with my database
  //I launch the report functionality as a Thread
  et = new ReportTh(date1, date2);
  //I start the thread
  Thread th = new Thread(et);
  th.start();
  //to make my sample more compact I do not write Exception, but I have them.

}

public void cancelReport()
{
    et.terminate();
}

When I call "genReport()" with a button, appears a loading bar and a "Cancel" button in case I want to cancel the report.
but if I do not want to, I cant get to dissapear my loading box and appear a new one with a "Download" button.
Here is my code for the buttons:

<p:commandButton id="genReport" value="Generar" widgetVar="genButton" actionListener="#{reportBean.genReport}" onclick="PF('statusDialog').show();" update="panel1"  icon="ui-icon-check" ajax="true" />

<p:dialog widgetVar="statusDialog" modal="true" draggable="false" closable="false" resizable="false" showHeader="false" >
   <h:panelGrid columns="1" cellpadding="2">
      <p:graphicImage name="ajaxloadingbar.gif" />
   </h:panelGrid>
   <p:commandButton id="CancelReport" value="Cancelar" widgetVar="canButton" actionListener="#{electroBean.cancelReport}"/>
</p:dialog>

<p:dialog modal="true" resizable="false" header="Values" widgetVar="dlg" showEffect="fold">
   <p:panelGrid id="display" columns="2" columnClasses="label,value">
         <p:commandButton id="downloadLink" value="Descargar Report" widgetVar="desButton" >
              <p:fileDownload value="#{electroBean.prepDownload}" />
          </p:commandButton>
   </p:panelGrid>
</p:dialog>

I Hope someone can guide me or tell me if my approaching is not the correct one, what can I research.

Thanks in advance.