public class WordCount extends Configured implements Tool {

    /**
     * @author Edison Chou
     * @version 1.0
     */
    public static class MyMapper extends
            Mapper<LongWritable, Text, Text, LongWritable> {
        /*
         * @param KEYIN →k1 表示每一行的起始位置（偏移量offset）
         * 
         * @param VALUEIN →v1 表示每一行的文本内容
         * 
         * @param KEYOUT →k2 表示每一行中的每个单词
         * 
         * @param VALUEOUT →v2表示每一行中的每个单词的出现次数，固定值为1
         */
        protected void map(LongWritable key, Text value,
                Mapper<LongWritable, Text, Text, LongWritable>.Context context)
                throws java.io.IOException, InterruptedException {
            Counter sensitiveCounter = context.getCounter("Sensitive Words:", "Hello");
            
            String line = value.toString();
            // 这里假定Hello是一个敏感词
            if(line.contains("Hello")){
                sensitiveCounter.increment(1L);
            }
            String[] spilted = line.split(" ");
            for (String word : spilted) {
                context.write(new Text(word), new LongWritable(1L));
            }
        };
    }

    /**
     * @author Edison Chou
     * @version 1.0
     */
    public static class MyReducer extends
            Reducer<Text, LongWritable, Text, LongWritable> {
        /*
         * @param KEYIN →k2 表示每一行中的每个单词
         * 
         * @param VALUEIN →v2 表示每一行中的每个单词的出现次数，固定值为1
         * 
         * @param KEYOUT →k3表示每一行中的每个单词
         * 
         * @param VALUEOUT →v3 表示每一行中的每个单词的出现次数之和
         */
        protected void reduce(Text key,
                java.lang.Iterable<LongWritable> values,
                Reducer<Text, LongWritable, Text, LongWritable>.Context context)
                throws java.io.IOException, InterruptedException {
            long count = 0L;
            for (LongWritable value : values) {
                count += value.get();
            }
            context.write(key, new LongWritable(count));
        };
    }

    // 输入文件路径
    public static String INPUT_PATH = "hdfs://hadoop-master:9000/testdir/input/words.txt";
    // 输出文件路径
    public static String OUTPUT_PATH = "hdfs://hadoop-master:9000/testdir/output/wordcount";

    @Override
    public int run(String[] args) throws Exception {
        // 首先删除输出路径的已有生成文件
        FileSystem fs = FileSystem.get(new URI(INPUT_PATH), getConf());
        Path outPath = new Path(OUTPUT_PATH);
        if (fs.exists(outPath)) {
            fs.delete(outPath, true);
        }

        Job job = new Job(getConf(), "WordCount");
        // 设置输入目录
        FileInputFormat.setInputPaths(job, new Path(INPUT_PATH));
        // 设置自定义Mapper
        job.setMapperClass(MyMapper.class);
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(LongWritable.class);
        // 设置自定义Reducer
        job.setReducerClass(MyReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(LongWritable.class);
        // 设置输出目录
        FileOutputFormat.setOutputPath(job, new Path(OUTPUT_PATH));

        System.exit(job.waitForCompletion(true) ? 0 : 1);
        return 0;
    }

    public static void main(String[] args) {
        Configuration conf = new Configuration();
        try {
            int res = ToolRunner.run(conf, new WordCount(), args);
            System.exit(res);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}