<p>I have been given a requirement where I need to support multiple databases in the same instance, to support multi-tenancy. Each DB has an identical schema. The user logs into a specific database by choosing from a list, and all subsequent calls will go to that DB until they log out.</p>

<p>I want to hot swap the session factory inside a single HibernateDaoTemplate based on a parameter supplied by the client. </p>

<p>I can find lots of stuff on hot-swapping data sources (and all the transaction issues associated with that) but I want to hot swap session factories - retaining all the caching for each.</p>

<p>What's the easiest way to do this? Configure a HotSwappableTarget for the DaoTemplate? Can anyone point me to samples on how to do this?</p>

If all the databases are identical, then I can suggest using a single SessionFactory and providing your own implementations for the DataSource and Cache that are actually "tenant-aware". (Implementing these is fairly trivial: just maintain a map of tenant id -> real cache/real datasource and then delegate all calls to the appropriate one). Configure the single SessionFactory to use your tenant-aware Cache and DataSource. A ThreadLocal can be used to make the tenant ID of the current request available to any code that needs to know about it.
I have used this approach before successfully to support multi-tenancy.