Module io.sf.carte.echosvg.util
Package io.sf.carte.echosvg.util

Class SoftReferenceCache

java.lang.Object
io.sf.carte.echosvg.util.SoftReferenceCache
Direct Known Subclasses:
NamedProfileCache, URLImageCache
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:

  • First you add the key, this lets the cache know that someone is working on that key.
  • Then when the completed object is ready you put it into the cache.

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

    Fields
    Modifier and Type
    Field
    Description
    protected final Map<Object,SoftReference<Object>>
    map
    The map of cached objects.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    SoftReferenceCache()
    Let people create their own caches.
    protected
    SoftReferenceCache(boolean synchronous)
    Constructs a soft reference cache.

  • Method Summary

    Modifier and Type
    Method
    Description
    protected final void
    clearImpl(Object key)
    Clear the entry for key.
    void
    flush()
    Let people flush the cache (remove any cached data).
    protected final boolean
    isDoneImpl(Object key)
    Check if request(key) will return immediately with the Object.
    protected final boolean
    isPresentImpl(Object key)
    Check if request(key) will return with an Object (not putting you on the hook for it).
    protected final void
    putImpl(Object key, Object object)
    Associate object with key.
    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.

    Methods inherited from class java.lang.Object

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

  • Field Details

  • Constructor Details

    • SoftReferenceCache

      protected SoftReferenceCache()
      Let people create their own caches.

    • SoftReferenceCache

      protected SoftReferenceCache(boolean synchronous)
      Constructs a soft reference cache.
      Parameters:
      synchronous - true to enable synchronous mode, false to enable waiting on requestImpl() until another thread adds the missing object

  • Method Details

    • 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.

    • 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).

    • 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.

    • 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.

    • 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.

    • 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.