hadoop--单表关联

给出child-parent表，输出grandchild-grandparent表child parentTom LucyTom JackJone LucyLucy MaryLucy BenJack AliceJack JesseTerry AliceTerry JessePhilip TerryPhilip AlmaMark TerryMark 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：