/**
* 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.hadoop.mapreduce;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.mapreduce.lib.partition.HashPartitioner;
/**
* A read-only view of the job that is provided to the tasks while they
* are running.
*/
public class JobContext {
// Put all of the attribute names in here so that Job and JobContext are
// consistent.
protected static final String INPUT_FORMAT_CLASS_ATTR =
"mapreduce.inputformat.class";
protected static final String MAP_CLASS_ATTR = "mapreduce.map.class";
protected static final String COMBINE_CLASS_ATTR = "mapreduce.combine.class";
protected static final String REDUCE_CLASS_ATTR = "mapreduce.reduce.class";
protected static final String OUTPUT_FORMAT_CLASS_ATTR =
"mapreduce.outputformat.class";
protected static final String PARTITIONER_CLASS_ATTR =
"mapreduce.partitioner.class";
protected final org.apache.hadoop.mapred.JobConf conf;
private final JobID jobId;
public JobContext(Configuration conf, JobID jobId) {
this.conf = new org.apache.hadoop.mapred.JobConf(conf);
this.jobId = jobId;
}
/**
* Return the configuration for the job.
* @return the shared configuration object
*/
public Configuration getConfiguration() {
return conf;
}
/**
* Get the unique ID for the job.
* @return the object with the job id
*/
public JobID getJobID() {
return jobId;
}
/**
* Get configured the number of reduce tasks for this job. Defaults to
* <code>1</code>.
* @return the number of reduce tasks for this job.
*/
public int getNumReduceTasks() {
return conf.getNumReduceTasks();
}
/**
* Get the current working directory for the default file system.
*
* @return the directory name.
*/
public Path getWorkingDirectory() throws IOException {
return conf.getWorkingDirectory();
}
/**
* Get the key class for the job output data.
* @return the key class for the job output data.
*/
public Class<?> getOutputKeyClass() {
return conf.getOutputKeyClass();
}
/**
* Get the value class for job outputs.
* @return the value class for job outputs.
*/
public Class<?> getOutputValueClass() {
return conf.getOutputValueClass();
}
/**
* Get the key class for the map output data. If it is not set, use the
* (final) output key class. This allows the map output key class to be
* different than the final output key class.
* @return the map output key class.
*/
public Class<?> getMapOutputKeyClass() {
return conf.getMapOutputKeyClass();
}
/**
* Get the value class for the map output data. If it is not set, use the
* (final) output value class This allows the map output value class to be
* different than the final output value class.
*
* @return the map output value class.
*/
public Class<?> getMapOutputValueClass() {
return conf.getMapOutputValueClass();
}
/**
* Get the user-specified job name. This is only used to identify the
* job to the user.
*
* @return the job's name, defaulting to "".
*/
public String getJobName() {
return conf.getJobName();
}
/**
* Get the {@link InputFormat} class for the job.
*
* @return the {@link InputFormat} class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends InputFormat<?,?>> getInputFormatClass()
throws ClassNotFoundException {
return (Class<? extends InputFormat<?,?>>)
conf.getClass(INPUT_FORMAT_CLASS_ATTR, TextInputFormat.class);
}
/**
* Get the {@link Mapper} class for the job.
*
* @return the {@link Mapper} class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends Mapper<?,?,?,?>> getMapperClass()
throws ClassNotFoundException {
return (Class<? extends Mapper<?,?,?,?>>)
conf.getClass(MAP_CLASS_ATTR, Mapper.class);
}
/**
* Get the combiner class for the job.
*
* @return the combiner class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends Reducer<?,?,?,?>> getCombinerClass()
throws ClassNotFoundException {
return (Class<? extends Reducer<?,?,?,?>>)
conf.getClass(COMBINE_CLASS_ATTR, null);
}
/**
* Get the {@link Reducer} class for the job.
*
* @return the {@link Reducer} class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends Reducer<?,?,?,?>> getReducerClass()
throws ClassNotFoundException {
return (Class<? extends Reducer<?,?,?,?>>)
conf.getClass(REDUCE_CLASS_ATTR, Reducer.class);
}
/**
* Get the {@link OutputFormat} class for the job.
*
* @return the {@link OutputFormat} class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends OutputFormat<?,?>> getOutputFormatClass()
throws ClassNotFoundException {
return (Class<? extends OutputFormat<?,?>>)
conf.getClass(OUTPUT_FORMAT_CLASS_ATTR, TextOutputFormat.class);
}
/**
* Get the {@link Partitioner} class for the job.
*
* @return the {@link Partitioner} class for the job.
*/
@SuppressWarnings("unchecked")
public Class<? extends Partitioner<?,?>> getPartitionerClass()
throws ClassNotFoundException {
return (Class<? extends Partitioner<?,?>>)
conf.getClass(PARTITIONER_CLASS_ATTR, HashPartitioner.class);
}
/**
* Get the {@link RawComparator} comparator used to compare keys.
*
* @return the {@link RawComparator} comparator used to compare keys.
*/
public RawComparator<?> getSortComparator() {
return conf.getOutputKeyComparator();
}
/**
* Get the pathname of the job's jar.
* @return the pathname
*/
public String getJar() {
return conf.getJar();
}
/**
* Get the user defined {@link RawComparator} comparator for
* grouping keys of inputs to the reduce.
*
* @return comparator set by the user for grouping values.
* @see Job#setGroupingComparatorClass(Class) for details.
*/
public RawComparator<?> getGroupingComparator() {
return conf.getOutputValueGroupingComparator();
}
}