i have one application which is in java and for front end we are using JSF. and java bean .. and for back end as AS400 DB2.. so in this application we have one logging page(login.jsf), currently we are using this page for login to the application, so here i want to implement the Single sign on... so if there any best way please suggest me..
It depends on want kind of SSO you want to do.
Usually you want to have your users in a central registry like an Active Directory.
Therefor you usually configure the LDAP server within WebSphere. Afterwards you configure your application to use HTTP_BASIC authentication.
EDIT: http://www.redbooks.ibm.com/abstracts/redp4192.html (a little bit outdated, but should show most required steps)
The best idea is probably to have a look at the Red Books, search in the Info-Center and bug the IBM support with some PMRs until you got it running. :)
You have to setup your LDAP as a federated repository, enable SSO and secure your application with JAAS.