在Ubuntu 16.04中使用JAVA中的MapReduce在文本文件中搜索给定单词

Question

I have to make a project to find a given word (string). This string will be inputted by the user. Then find the occurrence of the word in a particular text file stored in HDFS. The output should tell the presence of the word string.

package stringSearchJob;
import java.io.IOException;
import java.util.Scanner;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

public class StringSearch{
    public static void main(String argv[]) throws Exception {
        try {
            if (argv.length<3) {
                System.err.println("Give the input/ output/ keyword!");
                return;
            }
            JobConf conf = new JobConf(StringSearch.class);
            Job job = new Job(conf,"StringSearch");

            FileInputFormat.addInputPath(job, new Path(argv[0]));
            FileOutputFormat.setOutputPath(job, new Path(argv[1]));
            conf.set("search", argv[2]);

            job.setJarByClass(StringSearch.class);
            job.setMapperClass(WordMapper.class);
            job.setNumReduceTasks(0);

            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);

            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(IntWritable.class);

            JobClient.runJob(conf); 
            job.waitForCompletion(true);
       }    
       catch (Exception e) {
           e.printStackTrace();
       }
  }    
  public static class WordMapper extends Mapper<LongWritable, Text, Text, IntWritable>{ 
    @Override 
    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            try {
                Configuration conf = context.getConfiguration();
                String search = conf.get("search");
                String line = value.toString();
                Scanner scanner = new Scanner(line);
                while (scanner.hasNext()) {
                    if (line.contains(search)) {
                        String line1 = scanner.next();
                        context.write(new Text(line1), new IntWritable(1));
                    }
                }
                scanner.close();
            }
            catch (IOException e){
                e.printStackTrace();
            }
            catch (InterruptedException e){
                e.printStackTrace();
            }
        }    
    }    
}

Is my code wrong? Because the output I get on Ubuntu-16.04 Terminal is not correct. The steps I followed are as follows:

1. After wring the above code, I exported it into a Runnable JAR file named as StringSearch.jar . The class name was StringSearch .

2. Now, on the Terminal I wrote the following commands:

    hadoop fs -mkdir /user hadoop fs -mkdir /user/hduser hadoop fs -mkdir /user/hduser/StringSearch hadoop fs -mkdir Stringsearch/input hadoop -fs -copyFromLocal sample.txt StringSearch/input hadoop jar StringSearchNew.jar StringSearch /user/hduser/StringSearch/input user/hduser/StringSearch/output 'Lord' 

3. And I am getting the errors as follows.

    17/08/20 19:17:35 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable 17/08/20 19:17:41 INFO Configuration.deprecation: session.id is deprecated. Instead, use dfs.metrics.session-id 17/08/20 19:17:41 INFO jvm.JvmMetrics: Initializing JVM Metrics with processName=JobTracker, sessionId= 17/08/20 19:17:41 INFO jvm.JvmMetrics: Cannot initialize JVM Metrics with processName=JobTracker, sessionId= - already initialized Exception in thread "main" org.apache.hadoop.mapred.InvalidJobConfException: Output directory not set in JobConf. at org.apache.hadoop.mapred.FileOutputFormat.checkOutputSpecs(FileOutputFormat.java:117) at org.apache.hadoop.mapreduce.JobSubmitter.checkSpecs(JobSubmitter.java:268) at org.apache.hadoop.mapreduce.JobSubmitter.submitJobInternal(JobSubmitter.java:139) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1290) at org.apache.hadoop.mapreduce.Job$10.run(Job.java:1287) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698) at org.apache.hadoop.mapreduce.Job.submit(Job.java:1287) at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:575) at org.apache.hadoop.mapred.JobClient$1.run(JobClient.java:570) at java.security.AccessController.doPrivileged(Native Method) at javax.security.auth.Subject.doAs(Subject.java:422) at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1698) at org.apache.hadoop.mapred.JobClient.submitJobInternal(JobClient.java:570) at org.apache.hadoop.mapred.JobClient.submitJob(JobClient.java:561) at org.apache.hadoop.mapred.JobClient.runJob(JobClient.java:870) at stringSearchJob.StringSearch.main(StringSearch.java:43) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.apache.hadoop.util.RunJar.run(RunJar.java:221) at org.apache.hadoop.util.RunJar.main(RunJar.java:136) 

I basically learned how to use Hadoop MapReduce from Internet only. When I tried to make the program in JAVA after going through all other similar answers, it didn't gave the output. I am a complete newbie to Hadoop and thus would benefit if you please help me to resort the issue. I don't get what's wrong in here!

---

After reading the answer, I edited the code and got the following errors:

    17/08/24 05:01:30 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
    Exception in thread "main" java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.hadoop.util.RunJar.run(RunJar.java:221)
at org.apache.hadoop.util.RunJar.main(RunJar.java:136)
Caused by: java.io.IOException: No FileSystem for scheme: hdfs
at org.apache.hadoop.fs.FileSystem.getFileSystemClass(FileSystem.java:2660)
at org.apache.hadoop.fs.FileSystem.createFileSystem(FileSystem.java:2667)
at org.apache.hadoop.fs.FileSystem.access$200(FileSystem.java:94)
at org.apache.hadoop.fs.FileSystem$Cache.getInternal(FileSystem.java:2703)
at org.apache.hadoop.fs.FileSystem$Cache.get(FileSystem.java:2685)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:373)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:172)
at org.apache.hadoop.fs.FileSystem.get(FileSystem.java:357)
at org.apache.hadoop.fs.Path.getFileSystem(Path.java:295)
at org.apache.hadoop.mapreduce.lib.input.FileInputFormat.addInputPath(FileInputFormat.java:520)
at stringSearchJob.StringSearch.main(StringSearch.java:28)
... 11 more

Answer 1

Set your input and output directory to JobConf object not Job object

You must change as below :

 FileInputFormat.setInputPaths(conf /*from job to conf*/, new Path(args[0]));
 FileOutputFormat.setOutputPath(conf /*from job to conf*/, new Path(args[1]));

So the modified code should look like as below:

if (argv.length<3) {
                System.err.println("Give the input/ output/ keyword!");
                return;
            }
            JobConf conf = new JobConf(StringSearch.class);
            Job job = new Job(conf,"StringSearch");

            FileInputFormat.setInputPaths(conf, new Path(args[0]));
     FileOutputFormat.setOutputPath(conf, new Path(args[1]));
            conf.set("search", argv[2]);

            job.setJarByClass(StringSearch.class);
            job.setMapperClass(WordMapper.class);
            job.setNumReduceTasks(0);

            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(IntWritable.class);

            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(IntWritable.class);

            JobClient.runJob(conf); 
            job.waitForCompletion(true);