com.lithium.flow.filer.CachedReadFiler.java Source code

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Here is the source code for com.lithium.flow.filer.CachedReadFiler.java

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/*
 * Copyright 2015 Lithium Technologies, Inc.
 *
 * 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 com.lithium.flow.filer;

import static com.google.common.base.Preconditions.checkNotNull;

import com.lithium.flow.util.Caches;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.ExecutionException;

import javax.annotation.Nonnull;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.tuple.Pair;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.LoadingCache;

/**
 * Decorates an instance of {@link Filer} to cache file reads.
 *
 * @author Matt Ayres
 */
public class CachedReadFiler extends DecoratedFiler {
    private final LoadingCache<String, Pair<Long, byte[]>> cache;

    public CachedReadFiler(@Nonnull Filer delegate) {
        super(checkNotNull(delegate));
        cache = Caches.build(path -> {
            try (InputStream in = delegate.readFile(path)) {
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                IOUtils.copy(in, out);
                return Pair.of(delegate.getRecord(path).getTime(), out.toByteArray());
            }
        }, CacheBuilder::softValues);
    }

    @Override
    @Nonnull
    public InputStream readFile(@Nonnull String path) throws IOException {
        checkNotNull(path);

        Pair<Long, byte[]> pair = cache.getIfPresent(path);
        if (pair != null && pair.getLeft().equals(super.getRecord(path).getTime())) {
            return new ByteArrayInputStream(pair.getRight());
        }

        try {
            return new ByteArrayInputStream(cache.get(path).getRight());
        } catch (ExecutionException e) {
            if (e.getCause() instanceof IOException) {
                throw (IOException) e.getCause();
            } else {
                throw new IOException(e);
            }
        }
    }
}