mapreduce项目统计hbase成绩表中 单科最高单科排名、总分排名代码
时间: 2023-02-05 14:53:14 浏览: 33
这是一个使用 MapReduce 来统计 HBase 中单科最高分排名和总分排名的例子:
```java
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.mapreduce.TableReducer;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
public class HBaseRankCalculator {
public static class RankMapper
extends TableMapper<Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(ImmutableBytesWritable row, Result value,
Context context) throws IOException, InterruptedException {
String val = Bytes.toString(value.getValue(
Bytes.toBytes("scores"), Bytes.toBytes("math")));
word.set(val);
context.write(word, one);
}
}
public static class RankReducer
extends TableReducer<Text, IntWritable, ImmutableBytesWritable> {
public void reduce(Text key, Iterable<IntWritable> values,
Context context) throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
Put put = new Put(Bytes.toBytes(key.toString()));
put.addColumn(Bytes.toBytes("ranks"), Bytes.toBytes("math"),
Bytes.toBytes(sum));
context.write(null, put);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = HBaseConfiguration.create();
Job job = new Job(conf, "HBase Rank Calculator");
job.setJarByClass(HBaseRankCalculator.class);
Scan scan = new Scan();
scan.addColumn(Bytes.toBytes("scores"), Bytes.toBytes("math"));
TableMapReduceUtil.initTableMapperJob("scores", scan,
RankMapper.class, Text.class, IntWritable.class, job);
TableMapReduceUtil.initTableReducer