I think I read the entire internet to figure out how to get sitemesh to handle my html paths without extension + API paths without extension. I was wrapped up in a straight jacket figuring this out, every turn seemed to break something else. Then I finally came upon this post.
<servlet>
<servlet-name>dispatcher</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>jsp</servlet-name>
<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>jsp</servlet-name>
<url-pattern>/WEB-INF/views/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>jsp</servlet-name>
<url-pattern>/WEB-INF/decorators/*</url-pattern>
</servlet-mapping>
Enter this in your dispatcher-servlet.xml
<mvc:default-servlet-handler/>