hadoop--单表关联

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给出child-parent表，输出grandchild-grandparent表

child parent
Tom Lucy
Tom Jack
Jone Lucy
Lucy Mary
Lucy Ben
Jack Alice
Jack Jesse
Terry Alice
Terry Jesse
Philip Terry
Philip Alma
Mark Terry
Mark Alma

代码：

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

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 STjoin {
    public static int time=0;
    public static class Map extends Mapper<LongWritable, Text, Text, Text>{
    @Override
        protected void map(LongWritable key, Text value,Context context)
                throws IOException, InterruptedException {
        String childname=new String();
        String parentname=new String();
        String relationtype=new String();
        String line=value.toString();
        int i=0;
        while(line.charAt(i)!=' '){
            i++;
        }
        String[] values={line.substring(0, i),line.substring(i+1)};
        if(values[0].compareTo("child")!=0){
            childname=values[0];
            parentname=values[1];
            relationtype="1";//左右表区分标志
            context.write(new Text(values[1]), new Text(relationtype+"+"+childname+"+"+parentname));
            //右表
            relationtype="2";
            context.write(new Text(values[0]), new Text(relationtype+"+"+childname+"+"+parentname));
        }
    }
 }

    public static class Reduce extends Reducer<Text, Text, Text, Text>{
        @Override
        protected void reduce(Text key, Iterable<Text> values,Context context)
                throws IOException, InterruptedException {
            if(time==0){
                //输出表头
                context.write(new Text("grandchild"), new Text("grandparent"));
                time++;
            }
            int grandchildnum=0;
            String grandchild[]=new String[10];
            int grandparentnum=0;
            String grandparent[]=new String[10];
            Iterator iterator=values.iterator();
            while(iterator.hasNext()){
                String record=iterator.next().toString();
                int len=record.length();
                int i=2;
                if(len==0)
                    continue;
                char relationtype=record.charAt(0);
                String childname=new String();
                String parentname=new String();
                //获取value-list中value的child
                while(record.charAt(i)!='+'){
                    childname=childname+record.charAt(i);
                    i++;
                }
                i=i+1;//越过加号
                //获取value-list中value的parent
                while(i<len){
                    parentname=parentname+record.charAt(i);
                    i++;
                }
                System.out.println("childname="+childname+" parentname="+parentname);
                //左表，取出child放入grandchild
                if(relationtype=='1'){
                    grandchild[grandchildnum]=childname;
                    grandchildnum++;
                }else{//右表，取出parent放入 grandparent
                    grandparent[grandparentnum]=parentname;
                    grandparentnum++;   
                }
            }
            //grandchild和grandparent数组求笛卡儿积
            if(grandparentnum!=0&&grandchildnum!=0){
                System.out.println("******执行成功************");
                for(int m=0;m<grandchildnum;m++){
                    for(int n=0;n<grandparentnum;n++){
                        context.write(new Text(grandchild[m]), new Text(grandparent[n]));
                    }
                }
            }
        }
    }
    public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
        Configuration conf=new Configuration();
        Job job=new Job(conf, "STJOIN");
        job.setJarByClass(STjoin.class);
        job.setMapperClass(Map.class);
        job.setReducerClass(Reduce.class);

        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        FileInputFormat.addInputPath(job, new Path("/input/st"));
        FileOutputFormat.setOutputPath(job, new Path("/output/st"));
        System.out.println(job.waitForCompletion(true) ? 0:1);
    }

}

结果：