jdbm.helper
Interface CachePolicy

All Known Implementing Classes:

MRU, SoftCache

public interface CachePolicy

CachePolicity is an abstraction for different cache policies. (ie. MRU, time-based, soft-refs, ...)

Version:

$Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $

Author:

Alex Boisvert, Dilum Ranatunga

Method Summary

void	addListener(CachePolicyListener listener) Add a listener to this cache policy.
java.util.Enumeration	elements() Enumerate through the objects currently in the cache.
java.lang.Object	get(java.lang.Object key) Obtain the object stored under the key specified.
void	put(java.lang.Object key, java.lang.Object value) Place an object in the cache.
void	remove(java.lang.Object key) Remove the object stored under the key specified.
void	removeAll() Remove all objects from the cache.
void	removeListener(CachePolicyListener listener) Remove a listener from this cache policy.

Method Detail

put

void put(java.lang.Object key,
         java.lang.Object value)
         throws CacheEvictionException

Place an object in the cache. If the cache does not currently contain an object for the key specified, this mapping is added. If an object currently exists under the specified key, the current object is replaced with the new object.

If the changes to the cache cause the eviction of any objects stored under other key(s), events corresponding to the evictions are fired for each object. If an event listener is unable to handle the eviction, and throws a cache eviction exception, that exception is propagated to the caller. If such an exception is thrown, the cache itself should be left as it was before the put() operation was invoked: the the object whose eviction failed is still in the cache, and the new insertion or modification is reverted.

Parameters:

key - key for the cached object

value - the cached object

Throws:

CacheEvictionException - propagated if, while evicting objects to make room for new object, an eviction listener encountered this problem.

get

java.lang.Object get(java.lang.Object key)

Obtain the object stored under the key specified.

Parameters:

key - key the object was cached under

Returns:

the object if it is still in the cache, null otherwise.

remove

void remove(java.lang.Object key)

Remove the object stored under the key specified. Note that since eviction notices are only fired when objects under different keys are evicted, no event is fired for any object stored under this key (see put( )).

Parameters:

key - key the object was stored in the cache under.

removeAll

void removeAll()

Remove all objects from the cache. Consistent with remove( ), no eviction notices are fired.

elements

java.util.Enumeration elements()

Enumerate through the objects currently in the cache.

addListener

void addListener(CachePolicyListener listener)
                 throws java.lang.IllegalArgumentException

Add a listener to this cache policy.

If this cache policy already contains a listener that is equal to the one being added, this call has no effect.

Parameters:

listener - the (non-null) listener to add to this policy

Throws:

java.lang.IllegalArgumentException - if listener is null.

removeListener

void removeListener(CachePolicyListener listener)

Remove a listener from this cache policy. The listener is found using object equality, not identity.

Parameters:

listener - the listener to remove from this policy