Why @RequestMapping may be ignored

Recently I had a problem with Spring MVC. My mappings made by @RequestMapping annotations were ignored, but I was sure that annotation processor was picking the bean correctly. It turned out that if you use org.springframework.web.servlet.handler.SimpleUrlHandlerMapping to do some mapping in XML then you need to include DefaultAnnotationHandlerMapping explicitly into your application context:

<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/>

This is not needed when you have only annotation-based mapping - then  DefaultAnnotationHandlerMapping is included by default. This is documented only in  JavaDoc so it may be hard to spot.