JobContext.java
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上传日期:2018-01-08
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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.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();
- }
- }