mapreduce序列化java代码

package demo;


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


import java.io.IOException;


import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;


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;


/**
 * 将自定义的map和reduce等类写一个文件中，创建静态内部类
 */
public class MTest {



/**
     * 自定义MR序列化对象，将分析字符串封装到对象（java POJO）
     * MR自定义序列化对象，实现org.apache.hadoop.io.Writable接口
     */
static class MyPo implements Writable{
private String date;//yyyy-MM-dd
private double temp;//气温
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
public double getTemp() {
return temp;
}
public void setTemp(double temp) {
this.temp = temp;
}
@Override
public void write(DataOutput out) throws IOException {
//将当前对象属性依次写入MR上下提供DataOutput参数中
out.writeUTF(date);//针对String类型的属性写入
out.writeDouble(temp);
}
@Override
public void readFields(DataInput in) throws IOException {
//将MR上下文环境中DataInput参数依次传入当前对象的每一个属性
this.date=in.readUTF();
this.temp=in.readDouble();
}


        @Override
        public String toString() {
        // TODO Auto-generated method stub
        return this.date;
        }
}
    static class MyMapper extends Mapper<LongWritable,Text,MyPo, DoubleWritable>{
    private MyPo keypo=new MyPo();//输出的key
    private DoubleWritable temp=new DoubleWritable();//输出的value
    @Override
    protected void map(LongWritable key, Text value,Context context)
    throws IOException, InterruptedException {
    //得到当前行
    String line=value.toString();
    //按空格分隔
    String[] arr=line.split("\\s+");
    if(arr==null||arr.length<1)
    return;
    //当前行分解的数据封装到自定义的序列化对象中
//     封装年-月
    keypo.setDate(arr[0]+"-"+arr[1]);//2016-3 
//     封装气温
    temp.set(new Double(arr[3]));
   
    //向MR上下文对象写入key-value对
    context.write(keypo, temp);
    }
    }
    static class MyReduce extends Reducer<MyPo, DoubleWritable, Text, Text>{
    private Text mykey=new Text();
    private Text myvalue=new Text();
    @Override
    protected void reduce(MyPo key, Iterable<DoubleWritable> iter,
    Context ctx) throws IOException, InterruptedException {
    // TODO Auto-generated method stub
    StringBuilder buf=new StringBuilder("[");
    for (DoubleWritable wea : iter) {
    buf.append(wea.get()+",");
   
   
    }
    String temp=buf.substring(0,buf.lastIndexOf(","))+"]";
   
    mykey.set(key.getDate());
   
    myvalue.set(temp);
   
    ctx.write(mykey, myvalue);
   
    }
    }
    
public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {

Configuration cfg=new Configuration();

Job job = Job.getInstance(cfg);

job.setJobName("我是一个序列化");

job.setJarByClass(MTest.class);

job.setMapperClass(MyMapper.class);

job.setOutputKeyClass(MyPo.class);

job.setMapOutputValueClass(DoubleWritable.class);

job.setOutputKeyClass(Text.class);

job.setOutputValueClass(Text.class);

job.setReducerClass(MyReduce.class);

//格式化
FileInputFormat.addInputPath(job, new Path("hdfs://cai4:9000/minput/wea.txt"));
        FileOutputFormat.setOutputPath(job, new Path("hdfs://cai4:9000/mouts"));



        boolean flag = job.waitForCompletion(true);

System.exit(flag?0:1);



}





}