Package com.globalmentor.cache

Interface Cache<Q,V>

Type Parameters:

Q - The type of query used to request data from the cache.

V - The type of value stored in the cache.

All Known Implementing Classes:

AbstractCache, AbstractFileCache

public interface Cache<Q,V>

A cache that can fetch information when needed.

A cached value is retrieved using a query. The value is stored in the cache as part of the cache data.

Author:

Garret Wilson

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	Cache.Data<VV>	Class for storing a value along with its expiration information and other information.

Method Summary

Modifier and Type	Method	Description
void	addCacheFetchListener(Q key, CacheFetchListener<Q,V> listener)	Adds a listener to listen for a value being fetched.
V	get(Q query)	Retrieves a value from the cache.
V	get(Q query, boolean deferFetch)	Retrieves a value from the cache.
Cache.Data<V>	getData(Q query)	Retrieves data from the cache.
Cache.Data<V>	getData(Q query, boolean deferFetch)	Retrieves data from the cache.
long	getExpiration()
boolean	isCached(Q query)	Determined if a non-stale value is in the cache.
boolean	isFetchSynchronous()
void	removeCacheFetchListener(Q key, CacheFetchListener<Q,V> listener)	Removes a listener to listen for a value being fetched.
void	setExpiration(long expiration)	Sets the life of an object in the cache.
void	setFetchSynchronous(boolean fetchSynchronous)	Sets whether fetching new values is synchronous.
V	uncache(Q query)	Removes a value from the cache.

Method Detail

isFetchSynchronous

boolean isFetchSynchronous()

Returns:

Whether fetching new values is synchronous.

setFetchSynchronous

void setFetchSynchronous(boolean fetchSynchronous)

Sets whether fetching new values is synchronous. Changing this value does not change the sychronicity of fetches that have already started but have not yet completed.

Parameters:

fetchSynchronous - Whether fetches for new values should occur synchronously.

getExpiration

long getExpiration()

Returns:

The life of an object in the cache, in milliseconds.

setExpiration

void setExpiration(long expiration)

Sets the life of an object in the cache.

Parameters:

expiration - The length of time, in milliseconds, to keep cached information.

addCacheFetchListener

void addCacheFetchListener(Q key,
                           CacheFetchListener<Q,V> listener)

Adds a listener to listen for a value being fetched.

Parameters:

key - The query for requesting a value from the cache.

listener - The listener to be notified when the value is fetched.

removeCacheFetchListener

void removeCacheFetchListener(Q key,
                              CacheFetchListener<Q,V> listener)

Removes a listener to listen for a value being fetched.

Parameters:

key - The query for requesting a value from the cache.

listener - The listener to be notified when the value is fetched.

isCached

boolean isCached(Q query)
          throws java.io.IOException

Determined if a non-stale value is in the cache.

Parameters:

query - The query for requesting a value from the cache.

Returns:

Whether the value associated with the given query is in the cache and not stale.

Throws:

java.io.IOException - if there was an error checking the cached information for staleness.

get

V get(Q query)
throws java.io.IOException

Retrieves a value from the cache. Values are fetched from the backing store if needed, and this method blocks until the data is fetched.

Parameters:

query - The query for requesting a value from the cache.

Returns:

The cached value.

Throws:

java.io.IOException - if there was an error fetching the value from the backing store.

get

V get(Q query,
      boolean deferFetch)
throws java.io.IOException

Retrieves a value from the cache. Values are fetched from the backing store if needed, with fetching optionally deferred until later.

Parameters:

query - The query for requesting a value from the cache.

deferFetch - Whether fetching, if needed, should be deffered and performed in an asynchronous thread.

Returns:

The cached value, or null if fetching was deferred.

Throws:

java.io.IOException - if there was an error fetching the value from the backing store.

getData

Cache.Data<V> getData(Q query)
               throws java.io.IOException

Retrieves data from the cache. Data is fetched from the backing store if needed, and this method blocks until the data is fetched.

Parameters:

query - The query for requesting data from the cache.

Returns:

The cached data.

Throws:

java.io.IOException - if there was an error fetching the data from the backing store.

getData

Cache.Data<V> getData(Q query,
                      boolean deferFetch)
               throws java.io.IOException

Retrieves data from the cache. Data is fetched from the backing store if needed, with fetching optionally deferred until later.

Parameters:

query - The query for requesting data from the cache.

deferFetch - Whether fetching, if needed, should be deffered and performed in an asynchronous thread.

Returns:

The cached data, or null if fetching was deferred.

Throws:

java.io.IOException - if there was an error fetching the value from the backing store.

uncache

V uncache(Q query)
   throws java.io.IOException

Removes a value from the cache.

Parameters:

query - The query for requesting a value from the cache.

Returns:

The previously cached value, even if stale, or null if there was no cached value.

Throws:

java.io.IOException - if there was an error removing the value from the cache.