7.6. Class Loading and Regions

When used to cluster state of application servers, applications deployed in the application tend to put instances of objects specific to their application in the cache (or in an HttpSession object) which would require replication. It is common for application servers to assign separate ClassLoader instances to each application deployed, but have JBoss Cache libraries referenced by the application server's ClassLoader.

To enable us to successfully marshal and unmarshal objects from such class loaders, we use a concept called regions. A region is a portion of the cache which share a common class loader (a region also has other uses - see Chapter 10, Eviction).

A region is created by using the Cache.getRegion(Fqn fqn, boolean createIfNotExists) method, and returns an implementation of the Region interface. Once a region is obtained, a class loader for the region can be set or unset, and the region can be activated/deactivated. By default, regions are active unless the InactiveOnStartup configuration attribute is set to true.