20170924MapReduce学习总结

Map过程

IntWritable one = new IntWritable(1);public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException{String []res=value.toString().split("\t");String url=res[28];context.write(new Text(url), one);} 

Reduce过程

public void reduce(Text key, Iterable<IntWritable> values,              Context context) throws IOException, InterruptedException{int sum = 0;        for(IntWritable value:values){            sum+=value.get();        }        context.write(new Text(key.toString()+":"+sum),NullWritable.get());} 

job过程

public static void main(String[] args) throws Exception{    Configuration conf =new Configuration();    Job job= Job.getInstance(conf,"Pv");    job.setJarByClass(PvUvjob.class);    Path in=new Path("/user/input/pv");    Path out=new Path("/user/output/pv");    FileInputFormat.addInputPath(job, in);    FileOutputFormat.setOutputPath(job, out);    job.setInputFormatClass(TextInputFormat.class);    job.setOutputFormatClass(TextOutputFormat.class);    job.setMapperClass(PvUvMap.class);    job.setReducerClass(PvUvReduce.class);    //map输出类型    job.setMapOutputKeyClass(Text.class);    job.setMapOutputValueClass(IntWritable.class);    //reduce 输出类型    job.setOutputKeyClass(Text.class);    job.setOutputValueClass(NullWritable.class);    job.setNumReduceTasks(1);    job.waitForCompletion(true);}