com.intelligentsia.dowsers.entity.store.CachedEntityStore.java Source code

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Here is the source code for com.intelligentsia.dowsers.entity.store.CachedEntityStore.java

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/**
 *        Licensed to the Apache Software Foundation (ASF) under one
 *        or more contributor license agreements.  See the NOTICE file
 *        distributed with this work for additional information
 *        regarding copyright ownership.  The ASF licenses this file
 *        to you 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 com.intelligentsia.dowsers.entity.store;

import java.util.concurrent.TimeUnit;

import com.google.common.base.Preconditions;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.util.concurrent.UncheckedExecutionException;
import com.intelligentsia.dowsers.entity.reference.Reference;
import com.intelligentsia.dowsers.entity.reference.References;

/**
 * <code>CachedEntityStore</code> adding cache functionality.
 * 
 * @author <a href="mailto:jguibert@intelligents-ia.com">Jerome Guibert</a>
 * 
 */
public class CachedEntityStore implements EntityStore {

    /**
     * Delegate {@link EntityStore}.
     */
    protected final EntityStore entityStore;

    private final LoadingCache<KeyCache, Object> entities;

    /**
     * Build a new instance of <code>CachedEntityStore</code> with default
     * cache:
     * <ul>
     * <li>Maximum size : 1000 elements</li>
     * <li>expire after access : 1 hour</li>
     * </ul>
     * 
     * @param entityStore
     * @throws NullPointerException
     */
    public CachedEntityStore(final EntityStore entityStore) throws NullPointerException {
        this(entityStore, CacheBuilder.newBuilder().maximumSize(1000).expireAfterAccess(1, TimeUnit.HOURS));
    }

    /**
     * Build a new instance of <code>CachedEntityStore</code>.
     * 
     * @param entityStore
     * @param cacheBuilder
     */
    public CachedEntityStore(final EntityStore entityStore, final CacheBuilder<Object, Object> cacheBuilder) {
        super();
        this.entityStore = Preconditions.checkNotNull(entityStore);
        /**
         * Add specific cache loader.
         */
        entities = cacheBuilder.build(new CacheLoader<KeyCache, Object>() {
            @Override
            public Object load(final KeyCache key) throws Exception {
                return entityStore.find(key.expectedType, key.reference);
            }
        });
    }

    @Override
    public Iterable<Reference> find(final Class<?> expectedType) throws NullPointerException {
        return entityStore.find(expectedType);
    }

    @Override
    public Iterable<Reference> find(final Reference reference) throws NullPointerException {
        return entityStore.find(reference);
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T> T find(final Class<T> expectedType, final Reference reference)
            throws EntityNotFoundException, NullPointerException, IllegalArgumentException {
        try {
            return (T) entities.getUnchecked(new KeyCache(expectedType, reference));
        } catch (final UncheckedExecutionException e) {
            throw new EntityNotFoundException(e);
        }
    }

    @Override
    public <T> void store(final T entity)
            throws NullPointerException, ConcurrencyException, IllegalArgumentException {
        entities.invalidate(new KeyCache(null, References.identify(entity)));
        entityStore.store(entity);
    }

    @Override
    public <T> void remove(final T entity) throws NullPointerException, IllegalArgumentException {
        entities.invalidate(new KeyCache(null, References.identify(entity)));
        entityStore.remove(entity);
    }

    @Override
    public void remove(final Reference reference) throws NullPointerException, IllegalArgumentException {
        entities.invalidate(new KeyCache(null, reference));
        entityStore.remove(reference);
    }

    /**
     * <code>KeyCache</code>.
     * 
     * @author <a href="mailto:jguibert@intelligents-ia.com">Jerome Guibert</a>
     * 
     */
    private static class KeyCache {
        private final Class<?> expectedType;
        private final Reference reference;

        public KeyCache(final Class<?> expectedType, final Reference reference) {
            super();
            this.expectedType = expectedType;
            this.reference = reference;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = (prime * result) + ((reference == null) ? 0 : reference.hashCode());
            return result;
        }

        @Override
        public boolean equals(final Object obj) {
            if (this == obj) {
                return true;
            }
            if (obj == null) {
                return false;
            }
            if (getClass() != obj.getClass()) {
                return false;
            }
            final KeyCache other = (KeyCache) obj;
            if (reference == null) {
                if (other.reference != null) {
                    return false;
                }
            } else if (!reference.equals(other.reference)) {
                return false;
            }
            return true;
        }
    }

}