title: Spring Integration - SftpPersistentAcceptOnceFileListFilter filters out new file / modified file
body: <p>I have added SftpPersistentAcceptOnceFileListFilter on my Sftp Outbound Gateway to filter out files that I have processed.</p>
  <pre><code>&lt;int-sftp:outbound-gateway id=&quot;gateway&quot;
    expression=&quot;payload&quot;
    request-channel=&quot;request&quot;
    remote-directory=&quot;main&quot;
    command-options=&quot;-R&quot;
    command=&quot;ls&quot;
    session-factory=&quot;sessionFactory&quot;
    filter=&quot;sftpPersistentAcceptOnceFileListFilter&quot;
    reply-channel=&quot;reply&quot;&gt;
  &lt;/int-sftp:outbound-gateway&gt;
  
   &lt;bean name=&quot;metadataStore&quot; class=&quot;org.springframework.integration.metadata.PropertiesPersistingMetadataStore&quot;&gt;
      &lt;property name=&quot;baseDirectory&quot; value=&quot;/temp&quot;/&gt;
  &lt;/bean&gt;
  
   &lt;bean id=&quot;sftpPersistentAcceptOnceFileListFilter&quot; class=&quot;org.springframework.integration.sftp.filters.SftpPersistentAcceptOnceFileListFilter&quot;&gt;
      &lt;constructor-arg name=&quot;store&quot; ref=&quot;metadataStore&quot;/&gt;
      &lt;constructor-arg name=&quot;prefix&quot; value=&quot;files/&quot;/&gt;
   &lt;/bean&gt;
  </code></pre>
  <p>For example I have this directory :</p>
  <pre><code>main
    --directoryA
      --file1.txt
      --file2.txt
      --file3.txt
  </code></pre>
  <p>During the first polling, everything seems working fine. Checked on the metadata store and the file1, file2, file3 were stored there. The next polling, payload returns empty since all the files are already in the store and they are all filtered out by the filter as expected. However when I tried to load another file, it is somehow filtered out and was not saved on the metadata store. The same happens when I upload a new version of file1.txt. I expected it will passed through the filter since the modified date changes but somehow it did not. Did I missed some configuration here?</p>
  <pre><code>main
    --directoryA
      --file1.txt
      --file2.txt
      --file3.txt
      **--file4.txt**
  </code></pre>