org.hibernate.MappingException: Could not read mapping document from URL: null

If you use tag @hibernate.class for generate hibernate mapping

http://xdoclet.sourceforge.net/xdoclet/tags/hibernate-tags.html#@hibernate_class__0__1_

Don't use commented lines between java doc block and you class declaration.

/**
* Author : Alexey Zavizionov
*
* @hibernate.class table="MY_CLASS"
*/
// <- here it is 
public class MyClass {  

Regards,
Alexey