org.apache.batik.util

Class SoftReferenceCache

public class SoftReferenceCache extends Object

This class manages a cache of soft references to objects that may take some time to load or create, such as images loaded from the network.

Adding an object is two fold:

If someone requests a key after it has been added but before it has been put they will be blocked until the put.

Field Summary
protected Mapmap
The map of cached objects.
Constructor Summary
protected SoftReferenceCache()
Let people create their own caches.
Method Summary
protected voidclearImpl(Object key)
Clear the entry for key.
voidflush()
Let people flush the cache (remove any cached data).
protected booleanisDoneImpl(Object key)
Check if request(key) will return immediately with the Object.
protected booleanisPresentImpl(Object key)
Check if request(key) will return with an Object (not putting you on the hook for it).
protected voidputImpl(Object key, Object object)
Associate object with key.
protected ObjectrequestImpl(Object key)
If this returns null then you are now 'on the hook'. to put the Object associated with key into the cache.

Field Detail

map

protected final Map map
The map of cached objects. Must not change after creation, so it's final.

Constructor Detail

SoftReferenceCache

protected SoftReferenceCache()
Let people create their own caches.

Method Detail

clearImpl

protected final void clearImpl(Object key)
Clear the entry for key. This is the easiest way to 'get off the hook'. if you didn't intend to get on it.

flush

public void flush()
Let people flush the cache (remove any cached data). Pending requests will be treated as though clear() was called on the key, this should cause them to go and re-read the data.

isDoneImpl

protected final boolean isDoneImpl(Object key)
Check if request(key) will return immediately with the Object. Note that it is possible that this will return true but between this call and the call to request the soft-reference will be cleared.

isPresentImpl

protected final boolean isPresentImpl(Object key)
Check if request(key) will return with an Object (not putting you on the hook for it). Note that it is possible that this will return true but between this call and the call to request the soft-reference will be cleared. So it is still possible for request to return NULL, just much less likely (you can always call 'clear' in that case).

putImpl

protected final void putImpl(Object key, Object object)
Associate object with key. 'object' is only referenced through a soft reference so don't rely on the cache to keep it around. If the map no longer contains our url it was probably cleared or flushed since we were put on the hook for it, so in that case we will do nothing.

requestImpl

protected final Object requestImpl(Object key)
If this returns null then you are now 'on the hook'. to put the Object associated with key into the cache.
Copyright B) 2008 Apache Software Foundation. All Rights Reserved.