dler</code></dd>
<dt>Throws:</dt>
<dd><code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/io/IOException.html" title="class or interface in java.io" class="external-link">IOException</a></code> - if an I/O error occurred during the upgrade</dd>
<dd><code><a href="../ServletException.html" title="class in jakarta.servlet">ServletException</a></code> - if the given <code>handlerClass</code> fails to be instantiated</dd>
<dt>Since:</dt>
<dd>Servlet 3.1</dd>
<dt>See Also:</dt>
<dd>
