Hadoop序列化

序列化

把内存中对象转换成字节序列（或其他数据传输协议）以便于存储到磁盘（持久化）和网络传输

反序列化

接收到的字节序列或者其他传输协议或者是磁盘的持久化数据转换成内存的对象

自定义bean对象实现序列化接口（Writable）

具体实现bean对象序列化步骤如下7步。
（1）必须实现Writable接口
（2）反序列化时，需要反射调用空参构造函数，所以必须有空参构造
（3）重写序列化方法
（4）重写反序列化方法
（5）注意反序列化的顺序和序列化的顺序完全一致
（6）要想把结果显示在文件中，需要重写toString()，可用”\t”分开，方便后续用。
（7）如果需要将自定义的bean放在key中传输，则还需要实现Comparable接口，因为MapReduce框中的Shuffle过程要求对key必须能排序。详见后面排序案例。

hello word

测试数据

1   13726230503 24681   24681   200
2   13826544101 264 0   200
3   13926435656 132 1512    200
4   13926251106 240 0   200
5   18211575961 1527    2106    200
6   18211575961 4116    1432    200
7   13560439658 1116    954 200
8   15920133257 3156    2936    200
9   13719199419 240 0   200
10  13660577991 6960    690 200
11  15013685858 3659    3538    200
12  15989002119 1938    180 200
13  13560439658 918 4938    200
14  13480253104 80  180 200
15  13602846565 1938    2910    200
16  13922314466 3008    3720    200
17  13502468823 7335    110349  200
18  18320173382 9531    2412    200
19  13925057413 11058   48243   200
20  13760778710 120 120 200
21  13560436666 2481    24681   200
22  13560436666 1116    954 200

hadoop 序列化和反序列化对象

package com.bigdata.mapreduce.flowdata;

import org.apache.hadoop.io.Writable;

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

public class FlowBean implements Writable {
    private long upFlow;
    private long downFlow;
    private long sumFlow;

    public FlowBean() {
    }

    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;
    }

    // 序列化
    public void write(DataOutput dataOutput) throws IOException {
        dataOutput.writeLong(upFlow);
        dataOutput.writeLong(downFlow);
        dataOutput.writeLong(sumFlow);
    }

    // 反序列 跟序列化顺序一致
    public void readFields(DataInput dataInput) throws IOException {
        upFlow = dataInput.readLong();
        downFlow = dataInput.readLong();
        sumFlow = dataInput.readLong();
    }
}

maper

package com.bigdata.mapreduce.flowdata;

import org.apache.hadoop.io.Writable;

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

public class FlowBean implements Writable {
    private long upFlow;
    private long downFlow;
    private long sumFlow;

    public FlowBean() {
    }

    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;
    }

    // 序列化
    public void write(DataOutput dataOutput) throws IOException {
        dataOutput.writeLong(upFlow);
        dataOutput.writeLong(downFlow);
        dataOutput.writeLong(sumFlow);
    }

    // 反序列 跟序列化顺序一致
    public void readFields(DataInput dataInput) throws IOException {
        upFlow = dataInput.readLong();
        downFlow = dataInput.readLong();
        sumFlow = dataInput.readLong();
    }
}

reducer

package com.bigdata.mapreduce.flowdata;

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

import java.io.IOException;

public class FlowReducer extends Reducer {
    private FlowBean sumFlow = new FlowBean();

    @Override
    protected void reduce(Text key, Iterable values, Context context) throws IOException, InterruptedException {
        long sumUpFlow = 0;
        long sumDownFlow = 0;
        for (FlowBean value : values) {
            sumUpFlow += value.getUpFlow();
            sumDownFlow += value.getDownFlow();
        }
        sumFlow.set(sumUpFlow, sumDownFlow);
        context.write(key, sumFlow);
    }
}

driver

package com.bigdata.mapreduce.flowdata;

import org.apache.hadoop.conf.Configuration;
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(new Configuration());

        //设置类路径
        job.setJarByClass(FlowDriver.class);
        job.setMapperClass(FlowMapper.class);
        job.setReducerClass(FlowReducer.class);

        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(FlowBean.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(FlowBean.class);

        FileInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        boolean b = job.waitForCompletion(true);
        System.exit(b ? 0 : 1);

    }
}

运行结果

13480253104 80  180 260
13502468823 7335    110349  117684
13560436666 3597    25635   29232
13560439658 2034    5892    7926
13602846565 1938    2910    4848
13660577991 6960    690 7650
13719199419 240 0   240
13726230503 24681   24681   49362
13760778710 120 120 240
13826544101 264 0   264
13922314466 3008    3720    6728
13925057413 11058   48243   59301
13926251106 240 0   240
13926435656 132 1512    1644
15013685858 3659    3538    7197
15920133257 3156    2936    6092
15989002119 1938    180 2118
18211575961 5643    3538    9181
18320173382 9531    2412    11943