Package org.castor.cache

As explained in org.exolab.castor.persist, LockEngine implements a persistence engine that caches objects in memory for performance reasons and thus eliminates the number of operations against the persistence storage.

Author:

Werner Guttmann

The main component of this package is the interface Cache, which declares the external functionality of a performance cache. Existing (and future) cache engines have to implement this interface, which extends Map. To obtain an instance of a particular cache engine, use CacheFactoryRegistry and its factory methods.

The remainder of this package are exceptions associated with cache interaction, an enumeration of all (currently) available cache types and a prototype for an (abstract) base class to assist future cache engine additions.

Configuration

Castor (as of release 0.9.6) allows for addition of user-defined cache implementations.

By default, the file castor.properties includes a section as follows:

#
# Cache implementations
#
org.castor.cache.Factories=\
  org.castor.cache.simple.NoCacheFactory,\
  org.castor.cache.simple.TimeLimitedFactory,\
  org.castor.cache.simple.CountLimitedFactory,\
  org.castor.cache.simple.UnlimitedFactory,\
  org.castor.cache.distributed.FKCacheFactory,\
  org.castor.cache.distributed.JcsCacheFactory,\
  org.castor.cache.distributed.JCacheFactory,\
  org.castor.cache.distributed.CoherenceCacheFactory,\
  org.castor.cache.distributed.OsCacheFactory,\
  org.castor.cache.hashbelt.FIFOHashbeltFactory,\
  org.castor.cache.hashbelt.LRUHashbeltFactory

To add your own performance cache implementation, please append the fully-qualified class name to this list as shown here:

#
# Cache implementations
#
org.castor.cache.Factories=\
  org.castor.cache.simple.NoCacheFactory,\
  org.castor.cache.simple.TimeLimitedFactory,\
  org.castor.cache.simple.CountLimitedFactory,\
  org.castor.cache.simple.UnlimitedFactory,\
  org.castor.cache.distributed.FKCacheFactory,\
  org.castor.cache.distributed.JcsCacheFactory,\
  org.castor.cache.distributed.JCacheFactory,\
  org.castor.cache.distributed.CoherenceCacheFactory,\
  org.castor.cache.distributed.OsCacheFactory,\
  org.castor.cache.hashbelt.FIFOHashbeltFactory,\
  org.castor.cache.hashbelt.LRUHashbeltFactory,\
  org.whatever.somewhere.nevermind.CustomCache

In addition, you will have to provide the cache implementation and a CacheFactory implementation for your new cache instance. For this, please add an implementation of CacheFactory and make sure that you provide valid values for the two properties name and className.

To assist users in this task, a AbstractCacheFactory class has been supplied, which users should derive their custom CacheFactory instances from, if they wish so. Please consult existing CacheFactory implementations such as TimeLimitedFactory or CountLimitedFactory for code samples.

/**
 * My own cache implementation
 */
 public class CustomCache extends AbstractBaseCache {

    ...

 }

/**
 * My own cache factory implementation
 */
 public class CustomCacheFactory extends AbstractCacheFactory {

    /**
     * The name of the factory
     */
    private static final String NAME = "custom";

    /**
     * Full class name of the underlying cache implementation.
     */
    private static final String CLASS_NAME = "my.company.project.CustomCache";

    /**
     * Returns the short alias for this factory instance.
     * @return The short alias name.
     */
    public String getName() {
        return NAME;
    }

    /**
     * Returns the full class name of the underlying cache implementation.
     * @return The full cache class name.
     */
    public String getCacheClassName() {
        return CLASS_NAME;
    }

 }