To activate the functionality, this tags have to include in web.xml

<filter>
    <filter-name>filtroSes</filter-name>
    <filter-class>com.enjava.FiltroSes</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>filtroSes</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>INCLUDE</dispatcher>
    <dispatcher>ERROR</dispatcher>
  </filter-mapping>
  
   <listener>
    <listener-class>com.enjava.ListenerContexto</listener-class>
  </listener>
  
 
 
And in appengine-web.xml this tag too!    

  <sessions-enabled>true</sessions-enabled>
  
  

The library: https://github.com/downloads/juanantonioruz/servlet-session-gae/servlet-session-gae.jar

bye!

@Date 17.01.2012
@Author juanantonioruz@gmail.com