HTTPS in Google Application Engine

Now I'm playing with Google Application Engine.GAE is a terrific tool for learning requires. If you want to work with your application via HTTPS simple add the next lines to web.xml:
<security-constraint>
<web-resource-collection>
<web-resource-name>all</web-resource-name>
<url-pattern>/*</url-pattern>
</web-resource-collection>
<user-data-constraint>
<transport-guarantee>CONFIDENTIAL</transport-guarantee>
</user-data-constraint>
</security-constraint>

You do not need to buy a certificate and not need to configure anything.