hadoop上下文信息获取方法

 import java.io.IOException;
 import java.net.URI;

 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.io.LongWritable;
 import org.apache.hadoop.io.NullWritable;
 import org.apache.hadoop.io.Text;
 import org.apache.hadoop.mapreduce.Job;
 import org.apache.hadoop.mapreduce.JobID;
 import org.apache.hadoop.mapreduce.Mapper;
 import org.apache.hadoop.mapreduce.TaskAttemptID;
 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
 import org.apache.hadoop.mapreduce.lib.input.FileSplit;
 import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
 import org.apache.hadoop.util.GenericOptionsParser;

 public class GetIDMapReduce {
     public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
         Configuration conf = new Configuration();
        // String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
         if(args.length!=2){
             System.err.println("Usage databaseV1 <inputpath> <outputpath>");
         }

         Job job = Job.getInstance(conf, GetIDMapReduce.class.getSimpleName() + "1");
         job.setJarByClass(GetIDMapReduce.class);
         job.setMapOutputKeyClass(Text.class);
         job.setMapOutputValueClass(Text.class);
         job.setOutputKeyClass(Text.class);
         job.setOutputValueClass(NullWritable.class);
         job.setMapperClass(MyMapper1.class);
         job.setNumReduceTasks(0);
         job.setInputFormatClass(TextInputFormat.class);
         job.setOutputFormatClass(TextOutputFormat.class);
         FileInputFormat.addInputPath(job, new Path(args[0]));
         FileOutputFormat.setOutputPath(job, new Path(args[1]));
         job.waitForCompletion(true);
     }
     public static class MyMapper1 extends Mapper<LongWritable, Text, Text, NullWritable>{
         @Override
         protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, Text, NullWritable>.Context context)
                 throws IOException, InterruptedException {

             FileSplit fileSplit=(FileSplit) context.getInputSplit();
             String pathname=fileSplit.getPath().getName();
             JobID jobid=context.getJobID(); //获取jobid
             LongWritable keyout=context.getCurrentKey(); //获取key偏移量
             Text valueout=context.getCurrentValue();  //获取一行的值
             String jobname=context.getJobName();    //获得job名字
             TaskAttemptID taskid=context.getTaskAttemptID();    //获得taskid
             float progress=context.getProgress();   //获取任务执行进度
             String jar = context.getJar();  //作业运行之前，往集群拷贝的作业资源jar
             //String status = context.getStatus();
             String user = context.getUser(); //获取当前用户
             //String[] fileTimestamps = context.getFileTimestamps();
             int numReduceTasks = context.getNumReduceTasks(); //获得reduce的数量
             //Path[] fileClassPaths = context.getFileClassPaths();
             Configuration configuration = context.getConfiguration();   //获得作业配置文件
             //RawComparator<?> groupingComparator = context.getGroupingComparator();
             boolean jobSetupCleanupNeeded = context.getJobSetupCleanupNeeded(); //Get whether job-setup and job-cleanup is needed for the job
             int maxMapAttempts = context.getMaxMapAttempts(); //the max number of attempts per map task
             int maxReduceAttempts = context.getMaxReduceAttempts(); //he max number of attempts per reduce task.
             //@SuppressWarnings("deprecation")
             //Path[] localCacheFiles = context.getLocalCacheFiles();
             //OutputCommitter outputCommitter = context.getOutputCommitter();
             Path workingDirectory = context.getWorkingDirectory(); //工作目录
             boolean nextKeyValue = context.nextKeyValue();  //下一个键值对
             //URI[] cacheFiles = context.getCacheFiles();
             URI[] cacheArchives = context.getCacheArchives(); //Get cache archives set in the Configuration
             Path[] archiveClassPaths = context.getArchiveClassPaths();//Get the archive entries in classpath as an array of Path
             boolean profileEnabled = context.getProfileEnabled();//Get whether the task profiling is enabled.
             //String profileParams = context.getProfileParams();
             @SuppressWarnings("deprecation")
             boolean symlink = context.getSymlink();// Originally intended to check if symlinks should be used, but currently symlinks cannot be disabled
             //RawComparator<?> sortComparator = context.getSortComparator();
             //int hashCode = context.hashCode();
             context.write(new Text("===================================================================================="), NullWritable.get());
             context.write(new Text("pathname--"+pathname), NullWritable.get());
             context.write(new Text("jobid--"+jobid.toString()), NullWritable.get());
             context.write(new Text("keyout--"+keyout.toString()), NullWritable.get());
             context.write(new Text("keyout--"+valueout), NullWritable.get());
             context.write(new Text("jobname--"+jobname), NullWritable.get());
             context.write(new Text("taskid--"+taskid.toString()), NullWritable.get());
             context.write(new Text("progress--"+progress), NullWritable.get());
             context.write(new Text("jar--"+jar.toString()), NullWritable.get());
             //context.write(new Text("status--"+status), NullWritable.get());
             context.write(new Text("user--"+user), NullWritable.get());
             //context.write(new Text("fileTimestamps--"+fileTimestamps), NullWritable.get());
             context.write(new Text("numReduceTasks--"+numReduceTasks), NullWritable.get());
             //context.write(new Text("fileClassPaths--"+fileClassPaths), NullWritable.get());
             context.write(new Text("configuration--"+configuration), NullWritable.get());
             //context.write(new Text("groupingComparator--"+groupingComparator), NullWritable.get());
             context.write(new Text("jobSetupCleanupNeeded--"+jobSetupCleanupNeeded), NullWritable.get());
             context.write(new Text("maxMapAttempts--"+maxMapAttempts), NullWritable.get());
             context.write(new Text("maxReduceAttempts--"+maxReduceAttempts), NullWritable.get());
             //context.write(new Text("localCacheFiles--"+localCacheFiles), NullWritable.get());
             //context.write(new Text("outputCommitter--"+outputCommitter), NullWritable.get());
             context.write(new Text("workingDirectory--"+workingDirectory), NullWritable.get());
             context.write(new Text("nextKeyValue--"+nextKeyValue), NullWritable.get());
             //context.write(new Text("cacheFiles--"+cacheFiles), NullWritable.get());
             context.write(new Text("cacheArchives--"+cacheArchives), NullWritable.get());
             context.write(new Text("archiveClassPaths--"+archiveClassPaths), NullWritable.get());
             context.write(new Text("profileEnabled--"+profileEnabled), NullWritable.get());
             //context.write(new Text("profileParams--"+profileParams), NullWritable.get());
             context.write(new Text("symlink--"+symlink), NullWritable.get());
             //context.write(new Text("sortComparator--"+sortComparator), NullWritable.get());
             //context.write(new Text("hashCode--"+hashCode), NullWritable.get());
         }
     }
 }

注：并非原著，备注下来方便后面自己查看