I have my Session open in junit setUp(), and close in tearDown() methods.
My DAO layer takes the session as parameter and queries the db.
query is set to cacheable. What if i handle the session issue in web app using servlet filter or something. How does cache is going to behave after the session is closed in multi user environment. For example 1st user makes a request and loads the data into cache. servlet filter is going to close the session as soon as the response is returned. Now can the 2nd user use the cached result by the first user ? even after session is closed ?

Or should i leave the session open for the life of the application ?

Hibernate has a two level cache architecture. The session is first level local cache and should not be left open. The optional second level cache (default is ehcache) provides global caching. Read the wiki for information on the caching options. http://www.hibernate.org/hib_docs/reference/html/performance.html#performance-s3