自定义Writable类型

对处理较复杂数据时， Writable自带的类型不能满足要求，可以创建一个类是使用Writable接口，实现一个write()和readFields()方法，还需要无参的构造(用于反射)，和toString()(用于输出)

网上看到了一个统计手机流量的代码，大致数据如下

2323,13083012211,apmac,acmac,host,type,pack,pack,1000,1200,yes2323,13083012211,apmac,acmac,host,type,pack,pack,1000,1200,yes2323,13083012211,apmac,acmac,host,type,pack,pack,1000,1200,yes2323,13083012204,apmac,acmac,host,type,pack,pack,200,300,yes2323,13083012204,apmac,acmac,host,type,pack,pack,200,300,yes2323,13083012204,apmac,acmac,host,type,pack,pack,200,300,yes

其他数据不用关心， 只看第2第9第10 列的数据， 分别表示手机号， 上传流量， 下载流量

MapReduce类

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.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;public class DataCount {    public static class DCMapper extends Mapper<LongWritable, Text, Text, DataBean>{        @Override        protected void map(LongWritable key, Text value, Context context)                throws IOException, InterruptedException {            //accept             String line = value.toString();            //split            String[] fields = line.split(",");            System.out.println(fields[1]+" "+fields[8]+" "+fields[9]);            String tel = fields[1];            long up = Long.parseLong(fields[8]);            long down = Long.parseLong(fields[9]);              DataBean bean = new DataBean(tel, up, down);            //send            context.write(new Text(tel), bean);        }    }    public static class DCReducer extends Reducer<Text, DataBean, Text, DataBean>{        @Override        protected void reduce(Text key, Iterable<DataBean> values, Context context)                throws IOException, InterruptedException {            long up_sum = 0;            long down_sum = 0;            for(DataBean bean : values){                up_sum += bean.getUpPayLoad();                down_sum += bean.getDownPayLoad();            }            DataBean bean = new DataBean("", up_sum, down_sum);            context.write(key, bean);        }       }    public static void main(String[] args) throws Exception {        args = new String[]{"/input/data1","/output"};        Configuration conf = new Configuration();        Job job = Job.getInstance(conf);        job.setJarByClass(DataCount.class);        job.setMapperClass(DCMapper.class);        job.setMapOutputKeyClass(Text.class);        job.setMapOutputValueClass(DataBean.class);        FileInputFormat.setInputPaths(job, new Path(args[0]));        job.setReducerClass(DCReducer.class);        job.setOutputKeyClass(Text.class);        job.setOutputValueClass(DataBean.class);        FileOutputFormat.setOutputPath(job, new Path(args[1]));        job.waitForCompletion(true);    }}

自定义的Writable

package com.cyh;import java.io.DataInput;import java.io.DataOutput;import java.io.IOException;import org.apache.hadoop.io.Writable;public class DataBean implements Writable{    private String tel;    private long upPayLoad;    private long downPayLoad;    private long totalPayLoad;    public DataBean(){}    public DataBean(String tel, long upPayLoad, long downPayLoad) {        this.tel = tel;        this.upPayLoad = upPayLoad;        this.downPayLoad = downPayLoad;        this.totalPayLoad = upPayLoad + downPayLoad;    }    @Override    public String toString() {        return this.upPayLoad + "\t" + this.downPayLoad + "\t" + this.totalPayLoad;    }    // notice : 1 type 2 order    @Override    public void write(DataOutput out) throws IOException {        out.writeUTF(tel);        out.writeLong(upPayLoad);        out.writeLong(downPayLoad);        out.writeLong(totalPayLoad);    }    @Override    public void readFields(DataInput in) throws IOException {        this.tel = in.readUTF();        this.upPayLoad = in.readLong();        this.downPayLoad = in.readLong();        this.totalPayLoad = in.readLong();    }    public String getTel() {        return tel;    }    public void setTel(String tel) {        this.tel = tel;    }    public long getUpPayLoad() {        return upPayLoad;    }    public void setUpPayLoad(long upPayLoad) {        this.upPayLoad = upPayLoad;    }    public long getDownPayLoad() {        return downPayLoad;    }    public void setDownPayLoad(long downPayLoad) {        this.downPayLoad = downPayLoad;    }    public long getTotalPayLoad() {        return totalPayLoad;    }    public void setTotalPayLoad(long totalPayLoad) {        this.totalPayLoad = totalPayLoad;    }}