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if the SessionFactory is found, it is used to create Sessions to talk to the database. Also, the SessionFactory gets assigned with a timestamp (discussed later on), set to current time
if the SessionFactory is not found, it is created from the configurations and stored to the TGE Hibernate Session Factory Cache. Also, the SessionFactory gets assigned with a timestamp (discussed later on), set to current time
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then, each of the SessionFactories (in the TGE Hibernate Session Factory Cache) is checked whether current time minus 15 minutes is more than the timestamp (was the SessionFactory used within the last 15 minutes)
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