title: package org.apache.poi.ss.usermodel does not exist error
body: <p>I have a problem related to my adf application in jdeveloper 11g. When i build my application,i take these errors: </p>
  
  <p><img src="https://i.stack.imgur.com/b4OYp.png" alt="enter image description here"></p>
  
  <p>These errors in code-behind:</p>
  
  <pre><code>import org.apache.poi.ss.usermodel.Cell;
  import org.apache.poi.ss.usermodel.DateUtil;
  import org.apache.poi.ss.usermodel.Sheet;
  import org.apache.poi.ss.usermodel.Workbook;
  import org.apache.poi.ss.usermodel.WorkbookFactory;
  </code></pre>
  
  <p>I have investigated this error and i have learned that this error is related to apache poi. I have controlled my application and i have <strong>poi-3.9-20121203.jar</strong> file in my application folder : </p>
  
  <blockquote>
    <p>C:\roket1\ViewController\public_html\WEB-INF\lib</p>
  </blockquote>
  
  <p>What can i do to get rid of these errors ? 
  Thanks in advance.</p>