org.cdlib.xtf.cache

Class GeneratingCache<K,V>

Object

Cache<K,V>

GeneratingCache<K,V>

Direct Known Subclasses:

Authenticator.IpListCache, ConfigCache, ImageCache, StylesheetCache

public abstract class GeneratingCache<K,V>
extends Cache<K,V>

A cache that generates an entry if one isn't found. The generate() method must be supplied by the derived class.

Nested Class Summary

Nested classes/interfaces inherited from class Cache

Cache.ListEntry, Cache.NullIterator

Field Summary

Fields

Modifier and Type	Field and Description
private Cache.ListEntry	curEntry The entry being generated

Fields inherited from class Cache

ageList, keyMap

Constructor Summary

Constructors

Constructor and Description
GeneratingCache(int maxEntries, int maxTime) Constructor - sets up the parameters of the cache.

Method Summary

Modifier and Type	Method and Description
void	addDependency(Dependency d) Can be called by the generate() method to add a dependency to the key being generated.
V	find(K key) Check the cache for an entry matching the given key.
protected abstract V	generate(K key) Called when find() fails to locate an entry for the given key.

Methods inherited from class Cache

cleanup, clear, dependenciesValid, getDependencies, has, lastSet, logAction, remove, size

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

curEntry

private Cache.ListEntry curEntry

The entry being generated

Constructor Detail

GeneratingCache

public GeneratingCache(int maxEntries,
                       int maxTime)

Constructor - sets up the parameters of the cache.

Parameters:

maxEntries - Maximum # of entries. Beyond this, older ones will be removed. Zero means no limit.

maxTime - Time (in seconds) an entry can stay in the cache without being used. Entries older than this will be removed. Zero means no limit.

Method Detail

find

public V find(K key)
       throws Exception

Check the cache for an entry matching the given key. If not found, one is generated.

Parameters:

key - The key to look up

Returns:

Value corresponding to that key. Never null.

Throws:

Exception

addDependency

public void addDependency(Dependency d)

Can be called by the generate() method to add a dependency to the key being generated.

Parameters:

d - The dependency to add

generate

protected abstract V generate(K key)
                       throws Exception

Called when find() fails to locate an entry for the given key. This method must be supplied by the derived class, and must produce a value for the key, or throw an exception if it can't.

Parameters:

key - The key to generate a value for.

Returns:

The value for that key

Throws:

Exception - If a value cannot be generated for any reason.