On Jul 20, 2010, at 1:01 PM, James Carman wrote:
[SNIP]
> I have also been thinking a bit about
> how to best create proxies to things that have to be looked up (such
> as Spring beans) when they're deserialized. Basically, you need to
> use the writeReplace()/readResolve() mechanism so that you don't write
> out actual references to the Spring bean. That gave me another idea,
> commons-flyweight. Basically, a flyweight would be a stand-in for a
> more heavyweight object and it can be used to retrieve it (or
> readResolve() it). Here's some code I threw together really quick:
>
> public class Flyweight<T> implements Serializable
> {
> //**********************************************************************************************************************
> // Fields
> //**********************************************************************************************************************
>
> private static Map<String, Object> flyweights = new
> TreeMap<String, Object>();
> private final String id;
>
> //**********************************************************************************************************************
> // Static Methods
> //**********************************************************************************************************************
>
> public static <T> Flyweight<T> register(T object)
> {
> final String id = UUID.randomUUID().toString();
> flyweights.put(id, object);
> return new Flyweight<T>(id);
> }
>
> //**********************************************************************************************************************
> // Constructors
> //**********************************************************************************************************************
>
> private Flyweight(String id)
> {
> this.id = id;
> }
>
> //**********************************************************************************************************************
> // Other Methods
> //**********************************************************************************************************************
>
> protected T readResolve()
> {
> return getObject();
> }
>
> public T getObject()
> {
> return (T) flyweights.get(id);
> }
> }
>
> I haven't thought through the memory "leaks" and stuff yet. This is
> just a rough idea. Maybe this sort of thing belongs in [lang] rather
> as its own module.
>
I know what you mean; it's potentially not that much code. Maybe start in the
sandbox and, once everything's working satisfactorily, decide what to do with
it? As for memory, what if you actually put the map of flyweight id:instance
onto a Flyweights class and managed *its* id mappings statically/weakly? Then
a given Flyweight would just become expired whenever its owning Flyweights
instance () was no longer accessible, and its getObject could reflect that
somehow. Typically it would be a sign of a programming error if a Flyweight
associated with a given container were used after its container had been
reclaimed, so a simple exception might be enough. Just ruminating...
-Matt
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