Session Sharing between 2 EAR in deployed in same server, but EAR app1 is Spring and EAR app2 is Struts 1.2

Session Sharing between 2 EAR in deployed in same server, but EAR app1 is
Spring and EAR app2 is Struts 1.2

We are migrating an application which is in struts 1.2 to Spring 3.1. as
part of our initial analysis, we want to migrate only one main page to
Spring and later down the line migrate all the pages. Now page 1 is
migrated to Spring web technologies and deployed as an EAR, all the link
outs on the page 1 are pointing to struts application pages.
How to maintain a user session across both the ear, forward and backwards
from Spring context to Struts and Struts to Spring context. both flows
should work seamlessly.
Application server is Websphere.