com.cloudera.crunch.materialize.MaterializableIterable.java Source code

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Here is the source code for com.cloudera.crunch.materialize.MaterializableIterable.java

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/**
 * Copyright (c) 2011, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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.cloudera.crunch.materialize;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.cloudera.crunch.Pipeline;
import com.cloudera.crunch.impl.mr.run.CrunchRuntimeException;
import com.cloudera.crunch.io.ReadableSourceTarget;

public class MaterializableIterable<E> implements Iterable<E> {

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

    private final Pipeline pipeline;
    private final ReadableSourceTarget<E> sourceTarget;
    private Iterable<E> materialized;

    public MaterializableIterable(Pipeline pipeline, ReadableSourceTarget<E> source) {
        this.pipeline = pipeline;
        this.sourceTarget = source;
        this.materialized = null;
    }

    public ReadableSourceTarget<E> getSourceTarget() {
        return sourceTarget;
    }

    @Override
    public Iterator<E> iterator() {
        if (materialized == null) {
            pipeline.run();
            materialize();
        }
        return materialized.iterator();
    }

    public void materialize() {
        try {
            materialized = sourceTarget.read(pipeline.getConfiguration());
        } catch (IOException e) {
            LOG.error("Could not materialize: " + sourceTarget, e);
            throw new CrunchRuntimeException(e);
        }
    }
}