The cache user’s view of the CML is represented by cache regions. A cache region is a named entity that provides a single distinct namespace for cached objects, isolation of operations over cached objects and separate configuration. Each cache region has a single storage plug-in and a single eviction policy plug-in associated with it, as well as separate cache threshold values.
A cache region can contain multiple cache groups that are defined by the cache user. There is always a default cache group for each cache region. Cache groups are identified by their name and are usually used to group together objects on which a cache user can perform massive operations. If the user does not request a specific cache group, he or she always works with the default one (accessed by a cache faзade).
Cache Region Structure
The general action flow when working with the cache is the following:
1. The cache user gets a cache region using a RegionFactory.
2. The cache user accesses the default cache group through the cache faзade, or a different cache group using its name.
3. The cache user performs operations on the cached objects (create, put, remove and so on).
4. The cache group uses the storage plug-in that is bound to the cache region to find the appropriate object on which the operation should be performed.
5. The storage plug-in contacts the eviction policy plug-in about the operation being performed on the object so that the latter can determine which objects are to be removed if this is needed.
The eviction policy plug-in that is associated with the cache region can evict cached objects periodically if a certain threshold (cache size or cache objects count) is exceeded.
Applications can register invalidation listeners to receive notification when a cached object is invalidated and removed from the cache. These listeners are registered in a special entity, called the cache control, that pertains to the cache region. This mechanism works in both cases:
· When the application explicitly invalidated an object in the cache using the cache control entity
· When the applications invalidates an object using the cache faзade (or another cache group).