title: Apache Poi slow on generate xlsx file
body: <p>I switched from <em>HSSFWorkbook</em> to <em>XssFWorkbook</em> and the performance on create Excel are going down. I search and search and I find that the bad performance, on create <code>xlsx</code>, is a known problem. If i try to create a file with about 1000 rows takes 3-4 minutes, is too much.</p>
  
  <p>Is there a solution to improve speed?</p>
  
  <p>Thanks!</p>