Mapper,Reducer,Wrapper的Java模板

http://www.easyigloo.org/?p=1145


很多时候想要测试hadoop上的一个想法，要求快速创建并运行任务。每个任务包含了至少3个组件。

Mapper类
Reducer类
Wrapper类

下面的代码用以产生空模板，只是将变量替换成自己的类名

MAPPER
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MAPPER
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import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import java.io.IOException;

/* In case you are using Multiple outputs */
//import org.apache.hadoop.io.NullWritable;
//import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;

public class Mapper extends Mapper {
    private Configuration conf;
    private Text outputKey = new Text();
    private Text outputValue = new Text();
    private String line = null;

    /* In case you are using Multiple outputs */
    //private NullWritable outputValue = NullWritable.get();
    //private MultipleOutputs contextMulti = null;

    @Override
    public void setup(Mapper.Context context) {
        this.conf = context.getConfiguration();

        /* In case you are using Multiple outputs */
        //contextMulti = new MultipleOutputs(context);
    }

    @Override
    public void map(LongWritable key, Text values, Context context)
            throws IOException, InterruptedException {
    }

    @Override
    public void cleanup (Mapper.Context context)throws IOException, InterruptedException {

        /* In case you are using Multiple outputs */
        //contextMulti.close();
    }
}

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REDUCER
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import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

/* In case you are using Multiple outputs */
//import org.apache.hadoop.io.NullWritable;
//import org.apache.hadoop.mapreduce.lib.output.MultipleOutputs;

public class Reducer extends Reducer {
    private Configuration conf;
    private Text outputKey = new Text();
    private Text outputValue = new Text();
    private String line = null;

    /* In case you are using Multiple outputs */
    //private NullWritable outputValue = NullWritable.get();
    //private MultipleOutputs contextMulti = null;

    @Override
    public void setup(Reducer.Context context) {
        this.conf = context.getConfiguration();

        /* In case you are using Multiple outputs */
        //contextMulti = new MultipleOutputs(context);
    }

    @Override
    public void reduce(Text key, Iterable values, Context context)
            throws IOException, InterruptedException {
    }

    @Override
    public void cleanup(Reducer.Context context) {
        /* In case you are using Multiple outputs */
        //contextMulti.close();
    }
}
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WRAPPER
这个类用到下面两个类

https://sites.google.com/site/hadoopandhive/home/ExtendedFileUtil.java?attredirects=0&d=1

https://sites.google.com/site/hadoopandhive/home/StringUtil.java?attredirects=0&d=1

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import StringUtil;

import ExtendedFileUtil;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;
import java.text.ParseException;

public class  extends Configured implements Tool, Constants {
    private Configuration conf = null;
    private Job job = null;
    private String inputDirList = null;
    private String outputDir = null;
    private String[] filesToProcess = null;
    private int totalReducers = 0;
    private int jobRes = 0;
    private ExtendedFileUtil fileUtil = new ExtendedFileUtil();

    public static void main(String[] args) throws Exception {
         ob = new ();
        int jobRes = ToolRunner.run(ob, args);
    }

    public int run(String[] args)
            throws ClassNotFoundException, IOException, InterruptedException, ParseException {
        jobRes = readCmdArgs(args);
        if (jobRes == 0) {
            jobRes = readConfig();
        }
        if (jobRes == 0) {
            jobRes = runMrJob();
        }
        return jobRes;
    }

    private int readCmdArgs(String[] args) {
        if (args.length == 2) {
            inputDirList = args[0];
            outputDir = args[1];
        } else {
            printUsage();
            System.exit(1);
        }
        return 0;
    }

    private int readConfig() throws IOException, InterruptedException, ClassNotFoundException {
        conf = new Configuration();
        //conf.set("SET_NEW_CONFIG_NAME", SET_NEW_CONFIG_VALUE);
        job = new Job(conf);
        if ((job.getJar() == null) || (job.getJar() == "")) {
            job.setJarByClass(.class);
        }
        return 0;
    }

    private int runMrJob()
            throws IOException, InterruptedException, ClassNotFoundException {
        filesToProcess = fileUtil.getFilesOnly(inputDirList, true);
        job.setJobName("");
        TextInputFormat.addInputPaths(job, StringUtil.arrayToString(filesToProcess, ","));
        TextOutputFormat.setOutputPath(job, new Path(outputDir));
        System.out.println("Input Dir: " + inputDirList);
        System.out.println("Output Dir: " + outputDir);

        job.setMapperClass(Mapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(Text.class);

        job.setReducerClass(Reducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        totalReducers = Math.round((fileUtil.size(inputDirList) / 134217728) * 0.1F);
        totalReducers = Math.max(totalReducers, 1);
        job.setNumReduceTasks(totalReducers );
        deleteOutputDirectory(outputDir);
        jobRes = job.waitForCompletion(true) ? 0 : 1;
        deleteLogsDirectory();
        fileUtil.removeAllZeroByteFiles(outputDir);
        return 0;
    }

    private int deleteOutputDirectory(String outputDir) throws IOException {
        fileUtil.removeHdfsPath(new Path(outputDir).toString());
        return 0;
    }

    private int printUsage() {
        System.out.println("USAGE:
");
        return 0;
    }

    private int deleteLogsDirectory()
            throws IOException {
        Path outputLogPath = new Path(new Path(outputDir).toString() + "/" + "_logs");
        fileUtil.removeHdfsPath(outputLogPath.toString());
        return 0;
    }
}