Combiner应用

r囧r小猫 2024-04-19 07:00 60阅读 0赞

package MovieCount;
    
    import Use.Rates.UserRateTopN;
    import org.apache.hadoop.conf.Configuration;
    import org.apache.hadoop.fs.Path;
    import org.apache.hadoop.io.IntWritable;
    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;
    import org.codehaus.jackson.map.ObjectMapper;
    
    
    import java.io.IOException;
    import java.util.Comparator;
    import java.util.Map;
    import java.util.TreeMap;
    
    
    public class RateHotn {
        public static class RateHotMap extends Mapper<LongWritable, Text,Text, IntWritable>{
            //ObjectMapper是Jackson提供的一个类，作用是将java对象与json格式相互转化
            //ObjectMapper 通过 writeValue 系列方法 将 java 对 象序列化 为 json，并 将 json 存 储成不同的格式，String（writeValueAsString），Byte Array（writeValueAsString），Writer， File，OutStream 和 DataOutput。
            //ObjectMapper 通过 readValue 系列方法从不同的数据源像 String ， Byte Array， Reader，File，URL， InputStream 将 json 反序列化为 java 对象。
            ObjectMapper objectMapper = new ObjectMapper();
    
    
            @Override
            protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
                String line = value.toString();
                UserRateTopN userRateTopN = objectMapper.readValue(line, UserRateTopN.class);
                String movie  = userRateTopN.getMovie();
                context.write(new Text(movie),new IntWritable(1));
            }
        }
        public static class RateHotnReduce extends Reducer<Text,IntWritable,Text,IntWritable>{
            TreeMap<IntWritable,Text>map;
    
            @Override
            protected void setup(Context context) throws IOException, InterruptedException {
                map = new TreeMap<>(new Comparator<IntWritable>(){
    
                    @Override
                    public int compare(IntWritable o1, IntWritable o2) {
                        return o2.compareTo(o1);
                    }
                });
            }
    
            @Override
            protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
                Integer count = 0;
                for(IntWritable value:values){
                    count = count + value.get();
                }
                map.put(new IntWritable(count),new Text(key));
    
            }
    
            @Override
            protected void cleanup(Context context) throws IOException, InterruptedException {
                Configuration conf = context.getConfiguration();
                int suibian = conf.getInt("suibian",3);
                 for(int i = 0;i<suibian;i++){
                     Map.Entry<IntWritable,Text> entry = map.pollFirstEntry();
                     IntWritable count = entry.getKey();
                     Text movie = entry.getValue();
                     context.write(movie,count);
    
                 }
            }
        }
    
        public static void main(String[] args) throws IOException, ClassNotFoundException, InterruptedException {
            Configuration conf = new Configuration();
            conf.setInt("suibian",Integer.parseInt(args[0]));
            Job job = Job.getInstance(conf);
            job.setCombinerClass(RateHotnCombiner.class);
            job.setJarByClass(RateHotn.class);
            job.setMapperClass(RateHotMap.class);
            job.setReducerClass(RateHotnReduce.class);
    
            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(IntWritable.class);
    
            FileInputFormat.setInputPaths(job,new Path(""));
            FileOutputFormat.setOutputPath(job,new Path(""));
            boolean b = job.waitForCompletion(true);
            System.exit(b?0:1);
        }
    }

package MovieCount;
    
    import org.apache.hadoop.io.IntWritable;
    import org.apache.hadoop.io.Text;
    import org.apache.hadoop.mapreduce.Reducer;
    
    import java.io.IOException;
    
    public class RateHotnCombiner extends Reducer<Text, IntWritable,Text,IntWritable> {
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            Integer count = 0;
            for(IntWritable value:values){
                count ++;
    
            }
            context.write(key,new IntWritable(count));
        }
    }