org.apache.crunch.hadoop.mapreduce.TaskAttemptContextFactory.java Source code

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Here is the source code for org.apache.crunch.hadoop.mapreduce.TaskAttemptContextFactory.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.hadoop.mapreduce;

import java.lang.reflect.Constructor;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;

/**
 * A factory class that allows us to hide the fact that {@code TaskAttemptContext} is a class in
 * Hadoop 1.x.x and an interface in Hadoop 2.x.x.
 */
@SuppressWarnings("unchecked")
public class TaskAttemptContextFactory {

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

    private static final TaskAttemptContextFactory INSTANCE = new TaskAttemptContextFactory();

    public static TaskAttemptContext create(Configuration conf, TaskAttemptID taskAttemptId) {
        return INSTANCE.createInternal(conf, taskAttemptId);
    }

    private Constructor<TaskAttemptContext> taskAttemptConstructor;

    private TaskAttemptContextFactory() {
        Class<TaskAttemptContext> implClass = TaskAttemptContext.class;
        if (implClass.isInterface()) {
            try {
                implClass = (Class<TaskAttemptContext>) Class
                        .forName("org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl");
            } catch (ClassNotFoundException e) {
                LOG.fatal("Could not find TaskAttemptContextImpl class, exiting", e);
            }
        }
        try {
            this.taskAttemptConstructor = implClass.getConstructor(Configuration.class, TaskAttemptID.class);
        } catch (Exception e) {
            LOG.fatal("Could not access TaskAttemptContext constructor, exiting", e);
        }
    }

    private TaskAttemptContext createInternal(Configuration conf, TaskAttemptID taskAttemptId) {
        try {
            return (TaskAttemptContext) taskAttemptConstructor.newInstance(conf, taskAttemptId);
        } catch (Exception e) {
            LOG.error("Could not construct a TaskAttemptContext instance", e);
            return null;
        }
    }
}