hdfs MapReduce到haase

1. 上传数据到hdfs中

2. 写Map\Reduce过程

3. 输出结果到hbase中

Tips：

1. 因为map是从hdfs中取数据，因此没有太大变化；而reduce需要输出结果到hbase中，所以这里继承了 TableReduce<keyin,valuein,keyout>，这里没有valueout，但是规定TableReduce的 valueout必须是Put或者Delete实例。

2. 已经确定了输入输出路径，所以不用在eclipse中配置Run Configuration了。

import java.io.IOException;  
    import java.util.StringTokenizer;  
      
    import org.apache.hadoop.conf.Configuration;  
    import org.apache.hadoop.fs.Path;  
    import org.apache.hadoop.hbase.HBaseConfiguration;  
    import org.apache.hadoop.hbase.HColumnDescriptor;  
    import org.apache.hadoop.hbase.HTableDescriptor;  
    import org.apache.hadoop.hbase.client.HBaseAdmin;  
    import org.apache.hadoop.hbase.client.Put;  
    import org.apache.hadoop.hbase.mapreduce.TableOutputFormat;  
    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.LongWritable;  
    import org.apache.hadoop.io.NullWritable;  
    import org.apache.hadoop.io.Text;  
    import org.apache.hadoop.mapreduce.Job;  
    import org.apache.hadoop.mapreduce.Mapper;  
    import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;  
    import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;  
      
    public class WordCountHBase {  
      
        /** 
         * @param args 
         * @throws IOException  
         * @throws ClassNotFoundException  
         * @throws InterruptedException  
         */  
        public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {  
            // TODO Auto-generated method stub  
            String tablename = "wordcount";  
            Configuration conf = new Configuration();  
            conf.set(TableOutputFormat.OUTPUT_TABLE, tablename);  
            createHBaseTable(tablename);  
            Job job = new Job(conf,"WordCount table");  
            job.setJarByClass(WordCountHBase.class);  
            job.setNumReduceTasks(3);  
            job.setMapperClass(Map.class);  
            job.setReducerClass(Reduce.class);  
            job.setMapOutputKeyClass(Text.class);  
            job.setMapOutputValueClass(IntWritable.class);  
            job.setInputFormatClass(TextInputFormat.class);  
            job.setOutputFormatClass(TableOutputFormat.class);  
            // 设置输入目录   
            FileInputFormat.addInputPath(job, new Path("hdfs://master:9000/input/wordcount/*"));   
            System.exit(job.waitForCompletion(true)?0:1);  
        }  
      
        public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {  
            private final static IntWritable one = new IntWritable(1);  
            private Text text = new Text();   
              
            @Override  
            public void map(LongWritable key, Text value, Context context) throws IOException,InterruptedException{  
                String s = value.toString();  
                StringTokenizer st = new StringTokenizer(s);  
                while(st.hasMoreTokens()) {  
                    text.set(st.nextToken());  
                    context.write(text, one);  
                }  
            }  
        }  
          
        public static class Reduce extends TableReducer<Text, IntWritable, NullWritable> {  
              
            @Override  
            public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException,InterruptedException{  
                int sum = 0;  
                for(IntWritable i:values) {  
                    sum+=i.get();  
                }  
                Put put = new Put(Bytes.toBytes(key.toString()));  
                // row,columnFamily:column,value = word,content:count,sum   
                put.add(Bytes.toBytes("content"),Bytes.toBytes("count"),Bytes.toBytes(String.valueOf(sum)));  
                context.write(NullWritable.get(), put);  
            }  
        }  
        /**  
         * create a table  
         * @param tablename  
         * @throws IOException  
         */  
        public static void createHBaseTable(String tablename) throws IOException {  
            HTableDescriptor htd = new HTableDescriptor(tablename);  
            HColumnDescriptor col = new HColumnDescriptor("content");  
            htd.addFamily(col);  
            Configuration cfg = HBaseConfiguration.create();  
            HBaseAdmin admin = new HBaseAdmin(cfg);  
            if(admin.tableExists(tablename)) {  
                System.out.println("table exists,trying recreate table!");  
                admin.disableTable(tablename);  
                admin.deleteTable(tablename);  
                admin.createTable(htd);  
            }  
            else {  
                System.out.println("create new table:"+tablename);  
                admin.createTable(htd);  
            }  
        }  
    }