MapReduceTopK TreeMap

MapReduce TopK统计加排序中介绍的TopK在mapreduce的实现。

本案例省略的上面案例中的Sort步骤，改用TreeMap来实现获取前K个词

package TopK1;
import java.io.IOException;
import java.util.StringTokenizer;

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;

/**
 * 统计词频
 * @author zx
 * [email protected]
 */
public class WordCount {

	/**
	 * 读取单词
	 * @author zx
	 *
	 */
	public static class Map extends Mapper<Object,Text,Text,IntWritable>{

		IntWritable count = new IntWritable(1);

		@Override
		protected void map(Object key, Text value, Context context)
				throws IOException, InterruptedException {
			StringTokenizer st = new StringTokenizer(value.toString());
			while(st.hasMoreTokens()){
				String word = st.nextToken().replaceAll("\"", "").replace("'", "").replace(".", "");
				context.write(new Text(word), count);
			}
		}

	}

	/**
	 * 统计词频
	 * @author zx
	 *
	 */
	public static class Reduce extends Reducer<Text,IntWritable,Text,IntWritable>{

		@SuppressWarnings("unused")
		@Override
		protected void reduce(Text key, Iterable<IntWritable> values,Context context)
				throws IOException, InterruptedException {
			int count = 0;
			for (IntWritable intWritable : values) {
				count ++;
			}
			context.write(key,new IntWritable(count));
		}

	}

	@SuppressWarnings("deprecation")
	public static boolean run(String in,String out) throws IOException, ClassNotFoundException, InterruptedException{

		FileUtil.deleteFile(out);

		Configuration conf = new Configuration();

		Job job = new Job(conf,"WordCount1");
		job.setJarByClass(WordCount.class);
		job.setMapperClass(Map.class);
		job.setReducerClass(Reduce.class);

		// 设置Map输出类型
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        // 设置Reduce输出类型
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        // 设置输入和输出目录
        FileInputFormat.addInputPath(job, new Path(in));
        FileOutputFormat.setOutputPath(job, new Path(out));

        return job.waitForCompletion(true);
	}

}

package TopK1;

import java.io.IOException;
import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeMap;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
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.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.NullOutputFormat;

/**
 *
 * @author zx
 *[email protected]
 */
public class TopK {

	public static class TopKMap extends Mapper<Object, Text, IntWritable, IntWritable>{

		TreeMap<Integer,String> tm = new TreeMap<Integer,String>(new Comparator<Integer>() {

			/**
			 * treeMap中的元素逆序排列
			 * @param o1
			 * @param o2
			 * @return
			 */
			@Override
			public int compare(Integer o1, Integer o2) {
				return o2.compareTo(o1);
			}

		});
		int k = 0;

		@Override
		protected void cleanup(Context context) throws IOException,
				InterruptedException {
			Configuration conf = context.getConfiguration();
			Path topKPath = new Path(conf.get("topKOut"));
			FileSystem fs = topKPath.getFileSystem(conf);
			FSDataOutputStream fsDOS = fs.create(topKPath);
			Iterator<Integer> it = tm.keySet().iterator();
			while(it.hasNext()){
				Integer key = it.next();
				String value = tm.get(key).toString();
				String line = value + "\t" + key + "\r";
				fsDOS.write(line.getBytes(), 0, line.length());
			}
			fsDOS.flush();
			fsDOS.close();
		}

		@Override
		protected void setup(Context context) throws IOException,
				InterruptedException {
			k = Integer.parseInt(context.getConfiguration().get("K"));
		}

		@Override
		protected void map(Object key, Text value, Context context)
				throws IOException, InterruptedException {
			String[] parts = value.toString().split("\t");
			tm.put(Integer.parseInt(parts[1]),parts[0]);
			if(tm.size() > k){
				tm.remove(tm.lastKey());
			}
		}

	}

	@SuppressWarnings("deprecation")
	public static void main(String args[]) throws ClassNotFoundException, IOException, InterruptedException{

		if(args.length < 4){
			throw new IllegalArgumentException("要有4个参数:1，要统计的文本文件名。2，统计后的结果路径。3，topK的结果目录，4，K");
		}

		FileUtil.deleteFile(args[2]);

		//要统计字数的文本文件名
		String in = args[0];

		//统计字数后的结果
		String wordCount = args[1];

		in = FileUtil.loadFile(wordCount, "TopK1", in);

		//如果统计字数的job完成后就开始求topK
		if(WordCount.run(in, wordCount)){

			int k = Integer.parseInt(args[3]);
			Configuration conf = new Configuration();

			FileUtil.deleteFile(args[2]);
			conf.set("topKOut", args[2]);
			conf.set("K", k+"");

			Job job = new Job(conf,"TopK1");

			job.setJarByClass(TopK.class);
			job.setMapperClass(TopKMap.class);

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

			FileInputFormat.addInputPath(job, new Path(wordCount));
			job.setOutputFormatClass(NullOutputFormat.class);

			System.exit(job.waitForCompletion(true)?0:1);
		}

	}

}

package TopK1;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

/**
 *
 * @author zx
 *
 */
public class FileUtil {

	/**
	 * 上传数据文件到hdfs
	 * @param inputPath
	 * @param fileName
	 * @return
	 * @throws IOException
	 */
	public static String loadFile(String inputPath,String folder,String fileName) throws IOException{

		//获取数据文件的全路径

		if(null != folder && !"".equals(folder)){
			folder = folder + "/";
		}

		String srcPathDir = FileUtil.class.getProtectionDomain().getCodeSource().getLocation()
                .getFile() + folder + fileName;

		Path srcpath = new Path("file:///" + srcPathDir);

		Path dstPath = new Path(getJobRootPath(inputPath) + fileName);

		Configuration conf = new Configuration();

		FileSystem fs = dstPath.getFileSystem(conf);

		fs.delete(dstPath, true);

		fs.copyFromLocalFile(srcpath, dstPath);

		fs.close();

		return getJobRootPath(inputPath) + fileName;
	}

	/**
	 * 如果路径的最后不包哈“/”就加一个“/”
	 * @param path
	 * @return
	 */
	public static String getJobRootPath(String path){
		if(path.lastIndexOf("/") == path.length()-1){
			path = path.substring(0, path.lastIndexOf("/"));
		}
		return path.substring(0, path.lastIndexOf("/")+1);
	}

	public static void deleteFile(String ...filePath) throws IOException{
		Configuration conf = new Configuration();
		for (int i = 0; i < filePath.length; i++) {
			Path path = new Path(filePath[i]);
			FileSystem fs = path.getFileSystem(conf);
			fs.delete(path,true);
		}
	}

}

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