CollectionReaderWrapper.java

/*******************************************************************************
 * Copyright 2013
 * TU Darmstadt, FG Sprachtechnologie
 * 
 * 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.dkpro.bigdata.io.hadoop;

import java.io.IOException;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.RecordReader;
import org.apache.uima.UIMAException;
import org.apache.uima.cas.CAS;
import org.apache.uima.collection.CollectionException;
import org.apache.uima.collection.CollectionReader;
import org.apache.uima.fit.factory.JCasFactory;
import org.apache.uima.fit.factory.TypeSystemDescriptionFactory;
import org.apache.uima.resource.ResourceInitializationException;
import org.apache.uima.resource.metadata.TypeSystemDescription;
import org.apache.uima.util.Progress;

/**
 * Wraps an existing CollectionReader (UIMA) instance as RecordReader<Text, CASWritable> (Hadoop).
 * 
 * @author Johannes Simon
 */
public class CollectionReaderWrapper
    implements RecordReader<Text, CASWritable>
{

    final private CollectionReader reader;

    private TypeSystemDescription typeSystem;

    public CollectionReaderWrapper(CollectionReader reader)
    {
        this.reader = reader;
        try {
            typeSystem = TypeSystemDescriptionFactory.createTypeSystemDescription();
        }
        catch (ResourceInitializationException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void close()
        throws IOException
    {
        reader.close();
    }

    @Override
    public Text createKey()
    {
        return new Text();
    }

    @Override
    public CASWritable createValue()
    {
        return new CASWritable();
    }

    @Override
    public long getPos()
        throws IOException
    {
        Progress[] progressArr = reader.getProgress();
        for (Progress p : progressArr) {
            if (p.getUnit().equals(Progress.BYTES)) {
                return p.getCompleted();
            }
        }

        return 0;
    }

    private static float getPercent(long part, long total)
    {
        if (total == 0) {
            return 0.0f;
        }
        return (float) part / (float) total;
    }

    @Override
    public float getProgress()
        throws IOException
    {
        Progress[] progressArr = reader.getProgress();
        for (Progress p : progressArr) {
            // Use the first progress type that reports a total > 0
            if (p.getTotal() > 0) {
                return getPercent(p.getCompleted(), p.getTotal());
            }
        }

        return 0.0f;
    }

    @Override
    public boolean next(Text key, CASWritable value)
        throws IOException
    {

        try {
            if (!reader.hasNext()) {
                return false;
            }
            CAS nextCAS = JCasFactory.createJCas(typeSystem).getCas();
            reader.getNext(nextCAS);
            value.setCAS(nextCAS);

            return true;
        }
        catch (CollectionException e) {
            e.printStackTrace();
        }
        catch (UIMAException e) {
            e.printStackTrace();
        }

        // Error occured. Stop reading.
        return false;
    }

}