hadoop的一些基本功能

hadoop的一些基本功能

import org.apache.hadoop.fs.*; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; public class hdoopduqu extends FSDataInputStream { private static hdoopduqu myFSDataInputStream; private static InputStream inputStream; private hdoopduqu(InputStream in) { super(in); inputStream = in; } public static hdoopduqu getInstance(InputStream inputStream){ if (null == myFSDataInputStream){ synchronized (hdoopduqu.class){ if (null == myFSDataInputStream){ myFSDataInputStream = new hdoopduqu(inputStream); } } } return myFSDataInputStream; } public static String readline(FileSystem fileStatus){ try { // FSDataInputStream inputStream = fileStatus.open(remotePath); BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); String line = null; if ((line = bufferedReader.readLine()) != null){ bufferedReader.close(); inputStream.close(); return line; } } catch (IOException e) { e.printStackTrace(); } return null; } } import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; public class ifexit { public static void main(String[] args) { try { String fileName="tmp"; Configuration conf=new Configuration(); conf.set("fs.defaultFS", "hdfs://192.168.198.130:8020"); conf.set("fs.hdfs.impl", "org.apache.hadoop.hdfs.DistributedFileSystem"); FileSystem fs=FileSystem.get(conf); if(fs.exists(new Path(fileName))) { System.out.println("File exists"); }else { System.out.println("File doesnot exist"); } }catch (Exception e) { e.printStackTrace(); } } } import java.io.IOException; import java.util.Iterator; import java.util.StringTokenizer; import org.apache.hadoop.*; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Job; import org.apache.hadoop.mapreduce.Mapper; import org.apache.hadoop.mapreduce.Reducer; import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; import org.apache.hadoop.util.GenericOptionsParser; public class WordCount { public WordCount() { } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); String[] otherArgs = (new GenericOptionsParser(conf, args)).getRemainingArgs(); if(otherArgs.length < 2) { System.err.println("Usage: wordcount [...] "); System.exit(2); } Job job = Job.getInstance(conf, "word count"); job.setJarByClass(WordCount.class); job.setMapperClass(WordCount.TokenizerMapper.class); job.setCombinerClass(WordCount.IntSumReducer.class); job.setReducerClass(WordCount.IntSumReducer.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); for(int i = 0; i < otherArgs.length - 1; ++i) { FileInputFormat.addInputPath(job, new Path(otherArgs[i])); } FileOutputFormat.setOutputPath(job, new Path(otherArgs[otherArgs.length - 1])); System.exit(job.waitForCompletion(true)?0:1); } public static class TokenizerMapper extends Mapper { private static final IntWritable one = new IntWritable(1); private Text word = new Text(); public TokenizerMapper() { } public void map(Object key, Text value, Mapper.Context context) throws IOException, InterruptedException { StringTokenizer itr = new StringTokenizer(value.toString()); while(itr.hasMoreTokens()) { this.word.set(itr.nextToken()); context.write(this.word, one); } } } public static class IntSumReducer extends Reducer { private IntWritable result = new IntWritable(); public IntSumReducer() { } public void reduce(Text key, Iterable values, Reducer.Context context) throws IOException, InterruptedException { int sum = 0; IntWritable val; for(Iterator i$ = values.iterator(); i$.hasNext(); sum += val.get()) { val = (IntWritable)i$.next(); } this.result.set(sum); context.write(key, this.result); } } } 以上是实现读取hdfs数据，实现文件存在查询，以及对hdfs的一个文件进行字母数数的功能

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