org.apache.crunch.io.seq.SeqFileReaderFactory.java Source code

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Here is the source code for org.apache.crunch.io.seq.SeqFileReaderFactory.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 org.apache.crunch.io.seq;

import java.io.IOException;
import java.util.Iterator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.crunch.MapFn;
import org.apache.crunch.fn.IdentityFn;
import org.apache.crunch.io.FileReaderFactory;
import org.apache.crunch.io.impl.AutoClosingIterator;
import org.apache.crunch.types.Converter;
import org.apache.crunch.types.PTableType;
import org.apache.crunch.types.PType;
import org.apache.crunch.types.writable.Writables;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;

import com.google.common.collect.Iterators;
import com.google.common.collect.UnmodifiableIterator;

public class SeqFileReaderFactory<T> implements FileReaderFactory<T> {

    private static final Log LOG = LogFactory.getLog(SeqFileReaderFactory.class);

    private final Converter converter;
    private final MapFn<Object, T> mapFn;
    private final Writable key;
    private final Writable value;

    public SeqFileReaderFactory(PType<T> ptype) {
        this.converter = ptype.getConverter();
        this.mapFn = ptype.getInputMapFn();
        if (ptype instanceof PTableType) {
            PTableType ptt = (PTableType) ptype;
            this.key = SeqFileHelper.newInstance(ptt.getKeyType(), null);
            this.value = SeqFileHelper.newInstance(ptt.getValueType(), null);
        } else {
            this.key = NullWritable.get();
            this.value = SeqFileHelper.newInstance(ptype, null);
        }
    }

    public SeqFileReaderFactory(Class clazz) {
        PType<T> ptype = Writables.writables(clazz);
        this.converter = ptype.getConverter();
        this.mapFn = ptype.getInputMapFn();
        this.key = NullWritable.get();
        this.value = (Writable) ReflectionUtils.newInstance(clazz, null);
    }

    @Override
    public Iterator<T> read(FileSystem fs, final Path path) {
        mapFn.initialize();
        try {
            final SequenceFile.Reader reader = new SequenceFile.Reader(fs, path, fs.getConf());
            return new AutoClosingIterator<T>(reader, new UnmodifiableIterator<T>() {
                boolean nextChecked = false;
                boolean hasNext = false;

                @Override
                public boolean hasNext() {
                    if (nextChecked == true) {
                        return hasNext;
                    }
                    try {
                        hasNext = reader.next(key, value);
                        nextChecked = true;
                        return hasNext;
                    } catch (IOException e) {
                        LOG.info("Error reading from path: " + path, e);
                        return false;
                    }
                }

                @Override
                public T next() {
                    if (!nextChecked && !hasNext()) {
                        return null;
                    }
                    nextChecked = false;
                    return mapFn.map(converter.convertInput(key, value));
                }
            });
        } catch (IOException e) {
            LOG.info("Could not read seqfile at path: " + path, e);
            return Iterators.emptyIterator();
        }
    }

}