title: JSF rendered only if record is null
body: <p>The data shown in the table below is also displayed in my web app. With the exception of the <code>BOOKINGNO</code> column, which instead has an <code>h:commandButton</code>. The commandButton should only be rendered if the <code>BOOKINGNO</code> record is null on the corresponding row.</p>
  
  <p>At the moment, using the code below, the buttons are not rendering.</p>
  
  <h2>table sample</h2>
  
  <p><code>PLOTNO SITENO  ACCOMNO STARTDATE   ENDDATE     BOOKINGNO
   16     1       10      2014-10-01  2014-10-03  &lt;null&gt;
   21     2       2       2014-09-26  2014-09-29  923291
   22     2       3       2014-10-01  2014-10-03  &lt;null&gt;
   23     2       7       2014-09-26  2014-09-29  457235</code></p>
  
  <h2>JSF</h2>
  
  <pre><code>&lt;h:dataTable&gt; 
  
      ...
  
      &lt;h:column&gt;
          &lt;h:commandButton 
              onclick="if (!confirm('Do you want to book this holiday?')) return false"
              value="Book"
              action="#{dealsBean.book(item.plotNo)}"
              rendered="#{dealsBean.bookingNo = null}"&gt;
          &lt;/h:commandButton&gt;
      &lt;/h:column&gt;
  /&lt;h:dataTable&gt;
  </code></pre>
  
  <p>I've tried various different <code>rendered</code> arguments but none seem to do what I want.</p>
  
  <p>Am I getting the syntax right?</p>