As explained in {@link org.exolab.castor.jdo.persist}, {@link 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 {@link Cache.java}, which declares the external functionality of a performance cache. Existing (and future) cache engines have to implement this interface, which extends {@link java.util.Map}. To obtain an instance of a particular cache engine castor use {@link CacheRegistry} 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.jdo.cacheFactories=\
  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

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

# 
# Cache implementations
# 
org.castor.jdo.cacheFactories=\
  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.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 {@link CacheFactory} and make sure that you provide valid values for the two properties name and className.

To assist users in this task, a {@link AbstractCacheFactory} class has been supplied, which users should derive their custom {@link CacheFactory} instances from, if they wish so. Please consult existing {@link CacheFactory} implementations such as {@link TimeLimitedFactory} or {@link 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;   
    }
    
 }