9.3. Shipped Implementations
The currently available implementations shipped with JBoss Cache are as follows.
9.3.1. File system based cache loaders
JBoss Cache ships with several cache loaders that utilize the file system as a data store. They all require that the
<loader><properties> configuration element contains a location property, which maps to a directory to be used as a persistent store (e.g., location=/tmp/myDataStore ). Used mainly for testing and not recommended for production use.
FileCacheLoader, which is a simple filesystem-based implementation. By default, this cache loader checks for any potential character portability issues in the location or tree node names, for example invalid characters, producing warning messages. These checks can be disabled addingcheck.character.portabilityproperty to the<properties>element and setting it tofalse(e.g.,check.character.portability=false).The FileCacheLoader has some severe limitations which restrict its use in a production environment, or if used in such an environment, it should be used with due care and sufficient understanding of these limitations.- Due to the way the FileCacheLoader represents a tree structure on disk (directories and files) traversal is inefficient for deep trees.
- Usage on shared filesystems like NFS, Windows shares, etc. should be avoided as these do not implement proper file locking and can cause data corruption.
- Usage with an isolation level of NONE can cause corrupt writes as multiple threads attempt to write to the same file.
- File systems are inherently not transactional, so when attempting to use your cache in a transactional context, failures when writing to the file (which happens during the commit phase) cannot be recovered.
As a rule of thumb, it is recommended that the FileCacheLoader not be used in a highly concurrent, transactional or stressful environment, and its use is restricted to testing.BdbjeCacheLoader, which is a cache loader implementation based on the Oracle/Sleepycat's BerkeleyDB Java Edition.JdbmCacheLoader, which is a cache loader implementation based on the JDBM engine, a fast and free alternative to BerkeleyDB.
Note that the BerkeleyDB implementation is much more efficient than the filesystem-based implementation, and provides transactional guarantees, but requires a commercial license if distributed with an application (see http://www.oracle.com/database/berkeley-db/index.html for details).
