org.nickelproject.nickel.objectStore.CachingObjectStore.java Source code

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Here is the source code for org.nickelproject.nickel.objectStore.CachingObjectStore.java

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/*
 * Copyright (c) 2013 Nigel Duffy
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.nickelproject.nickel.objectStore;

import java.io.Serializable;
import java.util.concurrent.ExecutionException;

import org.apache.commons.lang3.SerializationUtils;
import org.nickelproject.nickel.blobStore.BlobRef;
import org.nickelproject.nickel.blobStore.BlobStore;
import org.nickelproject.util.RethrownException;
import org.nickelproject.util.tuple.Pair;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheBuilderSpec;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.cache.Weigher;
import com.google.inject.Inject;
import com.google.inject.Singleton;

@Singleton
public final class CachingObjectStore implements ObjectStore {
    private final BlobStore blobStore;
    private final LoadingCache<BlobRef, Pair<Integer, Object>> cache;

    @Inject
    public CachingObjectStore(final BlobStore bStore, final CacheBuilderSpec cacheBuilderSpec) {
        this.blobStore = bStore;
        this.cache = CacheBuilder.from(cacheBuilderSpec).weigher(new Weigher<BlobRef, Pair<Integer, Object>>() {
            @Override
            public int weigh(final BlobRef key, final Pair<Integer, Object> value) {
                return value.getA();
            }
        }).build(new CacheLoader<BlobRef, Pair<Integer, Object>>() {
            @Override
            public Pair<Integer, Object> load(final BlobRef key) throws Exception {
                final byte[] bytes = blobStore.get(key);
                if (bytes == null) {
                    throw new RuntimeException("Unable to load for key: " + key);
                } else {
                    return Pair.of(bytes.length, SerializationUtils.deserialize(bytes));
                }
            }
        });
    }

    @Override
    public boolean contains(final BlobRef blob) {
        return cache.getIfPresent(blob) != null || blobStore.contains(blob);
    }

    @Override
    public Object get(final BlobRef blob) {
        try {
            return contains(blob) ? cache.get(blob).getB() : null;
        } catch (final ExecutionException e) {
            throw RethrownException.rethrow(e);
        }
    }

    @Override
    public BlobRef put(final Object data) {
        final byte[] bytes = Util.bytesFromObject((Serializable) data);
        BlobRef blobRef = BlobRef.keyFromBytes(bytes);
        if (cache.getIfPresent(blobRef) == null) {
            blobRef = blobStore.put(bytes);
            cache.put(blobRef, Pair.of(bytes.length, data));
        }
        return blobRef;
    }
}