title: FlatFileItemWriter producing blank file
body: <p>I am using FlatFileItemWriter in the following way in order to produce a file containing a list of item in [id, FirstName] format-</p>
  
  <pre><code>&lt;bean id="FileWriter" class="org.springframework.batch.item.file.FlatFileItemWriter"&gt;
      &lt;property name="resource" value="processedtext.txt"/&gt;
      &lt;property name="shouldDeleteIfExists" value="true"/&gt;
      &lt;property name="lineAggregator"&gt;
          &lt;bean class="org.springframework.batch.item.file.transform.DelimitedLineAggregator"&gt;
              &lt;property name="delimiter" value="-"/&gt;
              &lt;property name="fieldExtractor"&gt;
                  &lt;bean class="org.springframework.batch.item.file.transform.BeanWrapperFieldExtractor"&gt;
                      &lt;property name="names" value="id,firstName"/&gt;
                  &lt;/bean&gt;
              &lt;/property&gt;
          &lt;/bean&gt;
      &lt;/property&gt;
  &lt;/bean&gt;
  </code></pre>
  
  <p>the Job ends with-
      17:19:23,720  INFO main SimpleJobLauncher:111 - Job: [FlowJob: [name=FileToFileJob]] completed with the following parameters: [{}] and the following status: [COMPLETED]</p>
  
  <p>The issue here is when I open the file processedtext.txt, it is blank.</p>
  
  <p>Can you please let me know if something is going wrong and how to resolve the issue.</p>