Chapter 8. Cache Loaders

8.1. The CacheLoader Interface and Lifecycle

8.2. Configuration

8.2.1. Singleton Store Configuration

8.3. Shipped Implementations

8.3.1. File system based cache loaders
8.3.2. Cache loaders that delegate to other caches
8.3.3. JDBCCacheLoader
8.3.4. TcpDelegatingCacheLoader
8.3.5. Transforming Cache Loaders

8.4. Cache Passivation

8.4.1. Cache Loader Behavior with Passivation Disabled vs. Enabled

8.5. Strategies

8.5.1. Local Cache With Store
8.5.2. Replicated Caches With All Caches Sharing The Same Store
8.5.3. Replicated Caches With Only One Cache Having A Store
8.5.4. Replicated Caches With Each Cache Having Its Own Store
8.5.5. Hierarchical Caches
8.5.6. Multiple Cache Loaders

JBoss Cache can use a CacheLoader to back up the in-memory cache to a backend datastore. If JBoss Cache is configured with a cache loader, then the following features are provided:

Whenever a cache element is accessed, and that element is not in the cache (e.g. due to eviction or due to server restart), then the cache loader transparently loads the element into the cache if found in the backend store.
Whenever an element is modified, added or removed, then that modification is persisted in the backend store via the cache loader. If transactions are used, all modifications created within a transaction are persisted. To this end, the CacheLoader takes part in the two phase commit protocol run by the transaction manager, although it does not do so explicitly.

^[6]Of course they can enable state transfer, if they want to have a warm or hot cache after startup.