IDEA上TopN案例

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FlowBean类：

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package com.atguigu.topn;

import org.apache.hadoop.io.WritableComparable;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

public class FlowBean implements WritableComparable<FlowBean> {
    private long upFlow;
    private long downFlow;
    private long sumFlow;

    @Override
    public String toString() {
        return upFlow + "\t" + downFlow + "\t" + sumFlow;
    }

    public void set(long upFlow,long downFlow){
        this.upFlow = upFlow;
        this.downFlow = downFlow;
        this.sumFlow = upFlow + downFlow;
    }

    public long getUpFlow() {
        return upFlow;
    }

    public void setUpFlow(long upFlow) {
        this.upFlow = upFlow;
    }

    public long getDownFlow() {
        return downFlow;
    }

    public void setDownFlow(long downFlow) {
        this.downFlow = downFlow;
    }

    public long getSumFlow() {
        return sumFlow;
    }

    public void setSumFlow(long sumFlow) {
        this.sumFlow = sumFlow;
    }

    @Override
    public void write(DataOutput dataOutput) throws IOException {
        dataOutput.writeLong(upFlow);
        dataOutput.writeLong(downFlow);
        dataOutput.writeLong(sumFlow);
    }

    @Override
    public void readFields(DataInput dataInput) throws IOException {
        upFlow = dataInput.readLong();
        downFlow = dataInput.readLong();
        sumFlow = dataInput.readLong();
    }

    @Override
    public int compareTo(FlowBean o) {
        return Long.compare(o.sumFlow,this.sumFlow);
    }
}

FlowMapper类：

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package com.atguigu.topn;

import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;

public class FlowMapper extends Mapper<LongWritable, Text,FlowBean,Text> {
    private FlowBean flow = new FlowBean();
    private Text phone = new Text();

    @Override
    protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String[] fields = value.toString().split("\t");
        phone.set(fields[0]);

        flow.set(Long.parseLong(fields[1]),Long.parseLong(fields[2]));
        context.write(flow,phone);
    }
}

FlowReducer类：

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package com.atguigu.topn;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

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

public class FlowReducer extends Reducer<FlowBean,Text, Text,FlowBean> {
    @Override
    protected void reduce(FlowBean key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        //因为所有数据都一样，进入了同一组，所以只取前10个即可
        Iterator<Text> iterator = values.iterator();
        for(int i = 0;i<10;++i){
            if(iterator.hasNext()){
                context.write(iterator.next(),key);
            }
        }
    }
}

FlowComparator类：

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package com.atguigu.topn;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;

/**
 * 让所有数据都分到同一组的比较器
 */
public class FlowComparator extends WritableComparator {
    protected FlowComparator() {
        super(FlowBean.class,true);
    }

    @Override
    public int compare(WritableComparable a, WritableComparable b) {
        return 0;//所有数据都一样，就都进入同一组
    }
}

FlowDriver类：

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package com.atguigu.topn;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

public class FlowDriver {
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Job job = Job.getInstance();

        job.setJarByClass(FlowDriver.class);
        job.setMapperClass(FlowMapper.class);
        job.setReducerClass(FlowReducer.class);

        job.setMapOutputKeyClass(FlowBean.class);
        job.setMapOutputValueClass(Text.class);
        job.setGroupingComparatorClass(FlowComparator.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(FlowBean.class);

        FileInputFormat.setInputPaths(job,new Path("F://input"));
        FileOutputFormat.setOutputPath(job,new Path("F://output"));
        boolean b = job.waitForCompletion(true);
        System.exit(b ? 0 : 1);
    }
}

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