first i think you should considere the drawbacks of a stateful webservices.
I'm 99% sure that there is not such thing in spring ws already ready to use.
I will not recommand to store them on database unless you may need some statistics on that.
Spring ws follows WS best pratices like contract first and stateless ws are not the case .
If you are interesting in caching stuff in session u should consider the scope of the bean (default is singleton) and maybe the ThreadLocal class already used by default for the authentification mecanism on spring security.
and maybe unless you want to reinvent the whell caching mecanism, use EhCache or else.
Spring have like always some cool glue stuff to simplify the Ehcache configuration . I have used it to cache authentification soap headers in order to not ask everytime the ldap.
Ehcache enable to maintain cache in network but need more configuration for that.
Last but not least you will need maybe a custom spring ws preprocessor because it is transversal and should not impact endPoint.
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