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    • org.xson.web.cache.WeakCache Maven / Gradle / Ivy

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    xco-web is an easy to use control layer framework, is part of the SOA system, using xml language to describe the controller.

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    package org.xson.web.cache;

import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.LinkedList;

public class WeakCache extends AbstractCache {
	private final LinkedList		hardLinksToAvoidGarbageCollection;
	private final ReferenceQueue	queueOfGarbageCollectedEntries;
	private final ICache					delegate;
	private int								numberOfHardLinks;

	public WeakCache(ICache delegate, int size) {
		this.delegate = delegate;
		// this.numberOfHardLinks = 256;
		this.numberOfHardLinks = size;
		this.hardLinksToAvoidGarbageCollection = new LinkedList();
		this.queueOfGarbageCollectedEntries = new ReferenceQueue();
	}

	@Override
	public String getId() {
		return delegate.getId();
	}

	@Override
	public int getSize() {
		removeGarbageCollectedItems();
		return delegate.getSize();
	}

	public void setSize(int size) {
		this.numberOfHardLinks = size;
	}

	// @Override
	// public void putObject(Object key, Object value) {
	// removeGarbageCollectedItems();
	// delegate.putObject(key, new WeakEntry(key, value, queueOfGarbageCollectedEntries));
	// }

	@Override
	public void putObject(Object key, Object value, Integer time) {
		removeGarbageCollectedItems();
		delegate.putObject(key, new WeakEntry(key, value, queueOfGarbageCollectedEntries));
	}

	@Override
	public Object getObject(Object key) {
		Object result = null;
		@SuppressWarnings("unchecked")
		// assumed delegate cache is totally managed by this cache
		WeakReference weakReference = (WeakReference) delegate.getObject(key);
		if (weakReference != null) {
			result = weakReference.get();
			if (result == null) {
				delegate.removeObject(key);
			} else {
				hardLinksToAvoidGarbageCollection.addFirst(result);
				if (hardLinksToAvoidGarbageCollection.size() > numberOfHardLinks) {
					hardLinksToAvoidGarbageCollection.removeLast();
				}
			}
		}
		return result;
	}

	@Override
	public Object removeObject(Object key) {
		removeGarbageCollectedItems();
		return delegate.removeObject(key);
	}

	@Override
	public void clear() {
		hardLinksToAvoidGarbageCollection.clear();
		removeGarbageCollectedItems();
		delegate.clear();
	}

	private void removeGarbageCollectedItems() {
		WeakEntry sv;
		while ((sv = (WeakEntry) queueOfGarbageCollectedEntries.poll()) != null) {
			delegate.removeObject(sv.key);
		}
	}

	private static class WeakEntry extends WeakReference {
		private final Object	key;

		private WeakEntry(Object key, Object value, ReferenceQueue garbageCollectionQueue) {
			super(value, garbageCollectionQueue);
			this.key = key;
		}
	}

}
    
    
    
    

    




    
    
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