大数据-WordCount在一堆给定的文本文件中统计输出每一个单词出现的总次数

cd /export/servers 
vim wordcount.txt

hello,world,hadoop 
hive,sqoop,flume,hello 
kitty,tom,jerry,world 
hadoop

hdfs dfs ‐mkdir /wordcount/ 
hdfs dfs ‐put wordcount.txt /wordcount/

    public class JobMain extends Configured implements Tool {
        @Override
        public int run(String[] args) throws Exception {
            Job job = Job.getInstance(super.getConf(), JobMain.class.getSimpleName());
            //打包到集群上面运行时候，必须要添加以下配置，指定程序的main函数 
            job.setJarByClass(JobMain.class);
            //第一步：读取输入文件解析成key，value对 
            job.setInputFormatClass(TextInputFormat.class);
            TextInputFormat.addInputPath(job, new Path("hdfs://192.168.52.250:8020/wordcount"));
            //第二步：设置我们的mapper类 
            job.setMapperClass(WordCountMapper.class);
            //设置我们map阶段完成之后的输出类型 
            job.setMapOutputKeyClass(Text.class);
            job.setMapOutputValueClass(LongWritable.class);
            //第三步，第四步，第五步，第六步，省略 
            // 第七步：设置我们的reduce类 
            job.setReducerClass(WordCountReducer.class);
            //设置我们reduce阶段完成之后的输出类型 
            job.setOutputKeyClass(Text.class);
            job.setOutputValueClass(LongWritable.class);
            //第八步：设置输出类以及输出路径 
            job.setOutputFormatClass(TextOutputFormat.class);
            TextOutputFormat.setOutputPath(job, new Path("hdfs://192.168.52.250:8020/wordcount_out"));
            boolean b = job.waitForCompletion(true);
            return b ? 0 : 1;
        }

        /*** 程序main函数的入口类 * @param args * @throws Exception */
        public static void main(String[] args) throws Exception {
            Configuration configuration = new Configuration();
            Tool tool = new JobMain();
            int run = ToolRunner.run(configuration, tool, args);
            System.exit(run);
        }
    }