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/**
 * Copyright 2012 Twitter, 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 parquet.hadoop.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Counter;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.JobID;
import org.apache.hadoop.mapreduce.MapContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.StatusReporter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.TaskInputOutputContext;

/*
 * This is based on ContextFactory.java from hadoop-2.0.x sources.
 */

/**
 * Utility methods to allow applications to deal with inconsistencies between
 * MapReduce Context Objects API between hadoop-0.20 and later versions.
 */
public class ContextUtil {

  private static final boolean useV21;

  private static final Constructor JOB_CONTEXT_CONSTRUCTOR;
  private static final Constructor TASK_CONTEXT_CONSTRUCTOR;
  private static final Constructor MAP_CONTEXT_CONSTRUCTOR;
  private static final Constructor MAP_CONTEXT_IMPL_CONSTRUCTOR;
  private static final Constructor GENERIC_COUNTER_CONSTRUCTOR;

  private static final Field READER_FIELD;
  private static final Field WRITER_FIELD;
  private static final Field OUTER_MAP_FIELD;
  private static final Field WRAPPED_CONTEXT_FIELD;

  private static final Method GET_CONFIGURATION_METHOD;
  private static final Method GET_COUNTER_METHOD;
  private static final Method INCREMENT_COUNTER_METHOD;

  static {
    boolean v21 = true;
    final String PACKAGE = "org.apache.hadoop.mapreduce";
    try {
      Class.forName(PACKAGE + ".task.JobContextImpl");
    } catch (ClassNotFoundException cnfe) {
      v21 = false;
    }
    useV21 = v21;
    Class jobContextCls;
    Class taskContextCls;
    Class taskIOContextCls;
    Class mapCls;
    Class mapContextCls;
    Class innerMapContextCls;
    Class genericCounterCls;
    try {
      if (v21) {
        jobContextCls =
            Class.forName(PACKAGE+".task.JobContextImpl");
        taskContextCls =
            Class.forName(PACKAGE+".task.TaskAttemptContextImpl");
        taskIOContextCls =
            Class.forName(PACKAGE+".task.TaskInputOutputContextImpl");
        mapContextCls = Class.forName(PACKAGE + ".task.MapContextImpl");
        mapCls = Class.forName(PACKAGE + ".lib.map.WrappedMapper");
        innerMapContextCls =
            Class.forName(PACKAGE+".lib.map.WrappedMapper$Context");
        genericCounterCls = Class.forName(PACKAGE+".counters.GenericCounter");
      } else {
        jobContextCls =
            Class.forName(PACKAGE+".JobContext");
        taskContextCls =
            Class.forName(PACKAGE+".TaskAttemptContext");
        taskIOContextCls =
            Class.forName(PACKAGE+".TaskInputOutputContext");
        mapContextCls = Class.forName(PACKAGE + ".MapContext");
        mapCls = Class.forName(PACKAGE + ".Mapper");
        innerMapContextCls =
            Class.forName(PACKAGE+".Mapper$Context");
        genericCounterCls =
            Class.forName("org.apache.hadoop.mapred.Counters$Counter");
      }
    } catch (ClassNotFoundException e) {
      throw new IllegalArgumentException("Can't find class", e);
    }
    try {
      JOB_CONTEXT_CONSTRUCTOR =
          jobContextCls.getConstructor(Configuration.class, JobID.class);
      JOB_CONTEXT_CONSTRUCTOR.setAccessible(true);
      TASK_CONTEXT_CONSTRUCTOR =
          taskContextCls.getConstructor(Configuration.class,
              TaskAttemptID.class);
      TASK_CONTEXT_CONSTRUCTOR.setAccessible(true);
      GENERIC_COUNTER_CONSTRUCTOR =
          genericCounterCls.getDeclaredConstructor(String.class,
              String.class,
              Long.TYPE);
      GENERIC_COUNTER_CONSTRUCTOR.setAccessible(true);

      if (useV21) {
        MAP_CONTEXT_CONSTRUCTOR =
            innerMapContextCls.getConstructor(mapCls,
                MapContext.class);
        MAP_CONTEXT_IMPL_CONSTRUCTOR =
            mapContextCls.getDeclaredConstructor(Configuration.class,
                TaskAttemptID.class,
                RecordReader.class,
                RecordWriter.class,
                OutputCommitter.class,
                StatusReporter.class,
                InputSplit.class);
        MAP_CONTEXT_IMPL_CONSTRUCTOR.setAccessible(true);
        WRAPPED_CONTEXT_FIELD =
            innerMapContextCls.getDeclaredField("mapContext");
        WRAPPED_CONTEXT_FIELD.setAccessible(true);
        Method get_counter_method;
        try {
          get_counter_method = Class.forName(PACKAGE + ".TaskAttemptContext").getMethod("getCounter", String.class,
                  String.class);
        } catch (Exception e) {
          get_counter_method = Class.forName(PACKAGE + ".TaskInputOutputContext").getMethod("getCounter",
                  String.class, String.class);
        }
        GET_COUNTER_METHOD=get_counter_method;
      } else {
        MAP_CONTEXT_CONSTRUCTOR =
            innerMapContextCls.getConstructor(mapCls,
                Configuration.class,
                TaskAttemptID.class,
                RecordReader.class,
                RecordWriter.class,
                OutputCommitter.class,
                StatusReporter.class,
                InputSplit.class);
        MAP_CONTEXT_IMPL_CONSTRUCTOR = null;
        WRAPPED_CONTEXT_FIELD = null;
        GET_COUNTER_METHOD=taskIOContextCls.getMethod("getCounter", String.class, String.class);
      }
      MAP_CONTEXT_CONSTRUCTOR.setAccessible(true);
      READER_FIELD = mapContextCls.getDeclaredField("reader");
      READER_FIELD.setAccessible(true);
      WRITER_FIELD = taskIOContextCls.getDeclaredField("output");
      WRITER_FIELD.setAccessible(true);
      OUTER_MAP_FIELD = innerMapContextCls.getDeclaredField("this$0");
      OUTER_MAP_FIELD.setAccessible(true);
      GET_CONFIGURATION_METHOD = Class.forName(PACKAGE+".JobContext")
          .getMethod("getConfiguration");
      INCREMENT_COUNTER_METHOD = Class.forName(PACKAGE+".Counter")
              .getMethod("increment", Long.TYPE);
    } catch (SecurityException e) {
      throw new IllegalArgumentException("Can't run constructor ", e);
    } catch (NoSuchMethodException e) {
      throw new IllegalArgumentException("Can't find constructor ", e);
    } catch (NoSuchFieldException e) {
      throw new IllegalArgumentException("Can't find field ", e);
    } catch (ClassNotFoundException e) {
      throw new IllegalArgumentException("Can't find class", e);
    }
  }

  /**
   * Creates JobContext from a JobConf and jobId using the correct constructor
   * for based on Hadoop version. jobId could be null.
   */
  public static JobContext newJobContext(Configuration conf, JobID jobId) {
    try {
      return (JobContext)
          JOB_CONTEXT_CONSTRUCTOR.newInstance(conf, jobId);
    } catch (InstantiationException e) {
      throw new IllegalArgumentException("Can't instantiate JobContext", e);
    } catch (IllegalAccessException e) {
      throw new IllegalArgumentException("Can't instantiate JobContext", e);
    } catch (InvocationTargetException e) {
      throw new IllegalArgumentException("Can't instantiate JobContext", e);
    }
  }

  /**
   * Creates TaskAttempContext from a JobConf and jobId using the correct
   * constructor for based on Hadoop version.
   */
  public static TaskAttemptContext newTaskAttemptContext(
      Configuration conf, TaskAttemptID taskAttemptId) {
    try {
      return (TaskAttemptContext)
          TASK_CONTEXT_CONSTRUCTOR.newInstance(conf, taskAttemptId);
    } catch (InstantiationException e) {
      throw new IllegalArgumentException("Can't instantiate TaskAttemptContext", e);
    } catch (IllegalAccessException e) {
      throw new IllegalArgumentException("Can't instantiate TaskAttemptContext", e);
    } catch (InvocationTargetException e) {
      throw new IllegalArgumentException("Can't instantiate TaskAttemptContext", e);
    }
  }

  /**
   * @return with Hadoop 2 : new GenericCounter(args),
* with Hadoop 1 : new Counter(args) */ public static Counter newGenericCounter(String name, String displayName, long value) { try { return (Counter) GENERIC_COUNTER_CONSTRUCTOR.newInstance(name, displayName, value); } catch (InstantiationException e) { throw new IllegalArgumentException("Can't instantiate Counter", e); } catch (IllegalAccessException e) { throw new IllegalArgumentException("Can't instantiate Counter", e); } catch (InvocationTargetException e) { throw new IllegalArgumentException("Can't instantiate Counter", e); } } /** * Invoke getConfiguration() method on JobContext. Works with both * Hadoop 1 and 2. */ public static Configuration getConfiguration(JobContext context) { try { return (Configuration) GET_CONFIGURATION_METHOD.invoke(context); } catch (IllegalAccessException e) { throw new IllegalArgumentException("Can't invoke method", e); } catch (InvocationTargetException e) { throw new IllegalArgumentException("Can't invoke method", e); } } public static Counter getCounter(TaskInputOutputContext context, String groupName, String counterName) { return (Counter) invoke(GET_COUNTER_METHOD, context, groupName, counterName); } /** * Invokes a method and rethrows any exception as runtime exceptions. */ private static Object invoke(Method method, Object obj, Object... args) { try { return method.invoke(obj, args); } catch (IllegalAccessException e) { throw new IllegalArgumentException("Can't invoke method " + method.getName(), e); } catch (InvocationTargetException e) { throw new IllegalArgumentException("Can't invoke method " + method.getName(), e); } } public static void incrementCounter(Counter counter, long increment) { invoke(INCREMENT_COUNTER_METHOD, counter, increment); } }




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