de.zib.gndms.model.util.GridResourceCache.java Source code

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Here is the source code for de.zib.gndms.model.util.GridResourceCache.java

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package de.zib.gndms.model.util;

/**
 * Copyright 2008-${YEAR} Zuse Institute Berlin (ZIB)
 * 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.
 *
 */

import com.google.common.cache.Cache;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import de.zib.gndms.model.common.GridResource;
import de.zib.gndms.model.common.NoSuchResourceException;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import java.util.concurrent.TimeUnit;

/**
 * @date:   ${DATE}
 * @time:   ${TIME}
 * @author: Jrg Bachmann
 * @email:  bachmann@zib.de
 */
public class GridResourceCache<G extends GridResource> {
    EntityManagerFactory emf;
    final Class<G> clazz;
    final Cache<String, G> cache;

    public static int MAX_CACHE_SIZE = 1000;

    public GridResourceCache(final Class<G> clazz, final EntityManagerFactory emf) {
        this.emf = emf;
        this.clazz = clazz;
        this.cache = CacheBuilder.newBuilder().expireAfterAccess(12, TimeUnit.HOURS).maximumSize(MAX_CACHE_SIZE)
                .initialCapacity(0).build(new GridResourceLoader<G>());
    }

    public GridResourceCache(final Class<G> clazz) {
        this.emf = null;
        this.clazz = clazz;
        this.cache = CacheBuilder.newBuilder().expireAfterAccess(12, TimeUnit.HOURS).maximumSize(MAX_CACHE_SIZE)
                .initialCapacity(0).build(new GridResourceLoader<G>());
    }

    public boolean exists(String id) {
        try {
            get(id);
        } catch (NoSuchResourceException e) {
            return false;
        }
        return true;
    }

    public G get(String id) throws NoSuchResourceException {
        try {
            return cache.get(id);
        } catch (Throwable e) {
            Throwable nested = e.getCause();

            if (nested instanceof NoSuchResourceException) {
                throw NoSuchResourceException.class.cast(nested);
            }

            throw new IllegalStateException("Serious problem while load resource with id " + id + ".", nested);
        }
    }

    public void invalidate(String id) {
        cache.invalidate(id);
    }

    private class GridResourceLoader<G extends GridResource> extends CacheLoader<String, G> {
        @Override
        @SuppressWarnings("unchecked")
        public G load(final String id) throws NoSuchResourceException {
            final EntityManager em = emf.createEntityManager();

            G g = (G) em.find(clazz, id);

            if (null == g)
                throw new NoSuchResourceException("No " + clazz.getCanonicalName() + " with id " + id + " found.");
            return g;
        }
    }

    public void setEmf(EntityManagerFactory emf) {
        this.emf = emf;
    }
}