好久没有更新博客了，最近复习了一下mapreduce，有一点忘记代码了，我还是弄一点模板。
import java.io.IOException;
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.Mapper;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.Reducer.Context;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;public class SortCount
{public static class SortMapperextends Mapper<LongWritable, Text, InfoBean, NullWritable> //map方法{private InfoBean i = new InfoBean();protected void map(LongWritable key, Text value, Mapper<LongWritable, Text, InfoBean, NullWritable>.Context context)throws IOException, InterruptedException{String line = value.toString();try{String[] fields = line.split("\\s+"); //正则表达式String name = fields[0];long sum = Long.parseLong(fields[1]);this.i.set(sum, name);context.write(this.i, NullWritable.get()); }catch (Exception e){e.printStackTrace();}}}public static class SortReducerextends Reducer<InfoBean, NullWritable, Text, InfoBean> //reduce方法{private Text t = new Text();private InfoBean i = new InfoBean();protected void reduce(InfoBean key, Iterable<NullWritable> values, Reducer<InfoBean, NullWritable, Text, InfoBean>.Context context)throws IOException, InterruptedException{String name = key.getName();this.t.set(name);this.i.set(key.getSum(), "");context.write(this.t, this.i);}}public static void main(String[] args)throws IOException, ClassNotFoundException, InterruptedException{Configuration conf = new Configuration();Job job = Job.getInstance(conf);job.setJarByClass(SortCount.class);job.setMapperClass(SortMapper.class);job.setMapOutputKeyClass(InfoBean.class);job.setMapOutputValueClass(NullWritable.class);FileInputFormat.setInputPaths(job, new Path[] { new Path(args[0]) });job.setReducerClass(SortReducer.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(InfoBean.class);FileOutputFormat.setOutputPath(job, new Path(args[1]));job.waitForCompletion(true);}
}import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.io.WritableComparable;public class InfoBeanimplements WritableComparable<InfoBean> //调用WritableComparable接口（其中包含排序），也可以调用Writable接口
{private long sum;private String name;public void set(long sum, String name){this.sum = sum;this.name = name;}public String toString(){return this.name + this.sum;}public long getSum(){return this.sum;}public void setSum(long sum){this.sum = sum;}public String getName(){return this.name;}public void setName(String name){this.name = name;}public void write(DataOutput out)throws IOException{out.writeUTF(this.name);out.writeLong(this.sum);}public void readFields(DataInput in)throws IOException{this.name = in.readUTF();this.sum = in.readLong();}public int compareTo(InfoBean arg0){return this.sum > arg0.getSum() ? -1 : 1;}
}