According to Caucho, you can run Drupal in Java now.

Following is the excerpt from Quercus website:

“Quercus is Caucho Technology’s 100% Java implementation of PHP 5 released under the Open Source GPL license. Quercus comes with many PHP modules and extensions like PDF, PDO, MySQL, and JSON. Quercus allows for tight integration of Java services with PHP scripts, so using PHP with JMS or Grails is a quick and painless endeavor.

With Quercus, PHP applications automatically take advantage of Java application server features just as connection pooling and clustered sessions.

Quercus implements PHP 5 and a growing list of PHP extensions including APC, iconv, GD, gettext, JSON, MySQL, Oracle, PDF, and Postgres. Many popular PHP application will run as well as, if not better, than the standard PHP interpreter straight out of the box. The growing list of PHP software certified running on Quercus includes DokuWiki, Drupal, Gallery2, Joomla, Mambo, Mantis, MediaWiki, Phorum, phpBB, phpMyAdmin, PHP-Nuke, Wordpress and XOOPS.”

This is very impressive. I am going to try installing Drupal over Quercus soon and share the experience.