驾驶员等级

public class abdDriver {

    public static void main(String arg[]) {
        try {
            Path input = new Path("amazon.txt");
            Path output = new Path("./outPutData");

            Configuration conf = new Configuration();
            Job job = Job.getInstance(conf);
            job.setJarByClass(abdDriver.class);

            job.setMapperClass(abdMapper.class);
            job.setMapOutputKeyClass(LongWritable.class);
            job.setMapOutputValueClass(Text.class);

            job.setReducerClass(abdReducer.class);
            job.setOutputKeyClass(NullWritable.class);
            job.setOutputValueClass(Text.class);

            job.setInputFormatClass(abdRecordReader.class);
            //job.setOutputFormatClass(TextOutputFormat.class);

            FileInputFormat.addInputPath(job, input);
            FileOutputFormat.setOutputPath(job, output);

            output.getFileSystem(job.getConfiguration()).delete(output, true);

            job.waitForCompletion(true);

            System.out.println("Completed successfully");

        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
}

Map类

public class abdMapper extends Mapper<LongWritable, abdRecordClass, LongWritable, Text> {

    @Override
    public void map(LongWritable key, abdRecordClass value, Context con) throws IOException, InterruptedException {
        if (value.getTITLE().toString().trim().length() > 0) {
            con.write(key, value.getTITLE());
            System.out.println(key + "\t" + value.getTITLE() + "\t" + value.getCATEGORIES());
        }
    }
}

减速器等级

public class abdReducer extends Reducer<LongWritable, Text, NullWritable, Text> {

    @Override
    public void reduce(LongWritable key, Iterable<Text> value, Context con) throws IOException, InterruptedException {
        System.out.println("reducer");

        for (Text t : value) {
            System.out.println(t);
            con.write(NullWritable.get(), t);
        }
    }

}

自定义可写类

public class abdRecordClass implements WritableComparable<abdRecordClass> {

    private Text ID, ASIN, TITLE, GROUP, SALESRANK, REV_SUMMARY,

    SIMILAR, CATEGORIES, REVIEWS;

    public abdRecordClass() {
        ID = new Text();
        ASIN = new Text();
        TITLE = new Text();
        GROUP = new Text();
        SALESRANK = new Text();
        REV_SUMMARY = new Text();
        SIMILAR = new Text();
        CATEGORIES = new Text();
        REVIEWS = new Text();
        ;
    }

    public abdRecordClass(Text id, Text asin, Text title, Text group, Text rank, Text similar, Text cat, Text rev_summary, Text reviews) {
        super();
        this.ID = id;
        this.ASIN = asin;
        this.TITLE = title;
        this.GROUP = group;
        this.SALESRANK = rank;
        this.SIMILAR = similar;
        this.CATEGORIES = cat;
        this.REV_SUMMARY = rev_summary;
        this.REVIEWS = reviews;
        System.out.println("new record created");
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        System.out.println("read fields");
        this.ID.readFields(in);
        this.ASIN.readFields(in);
        this.TITLE.readFields(in);
        this.GROUP.readFields(in);
        this.SALESRANK.readFields(in);
        this.SIMILAR.readFields(in);
        this.CATEGORIES.readFields(in);
        this.REV_SUMMARY.readFields(in);
        this.REVIEWS.readFields(in);

    }

    @Override
    public void write(DataOutput out) throws IOException {

        this.ID.write(out);
        System.out.println("write fields");
        this.ASIN.write(out);
        this.TITLE.write(out);
        this.GROUP.write(out);
        this.SALESRANK.write(out);
        this.SIMILAR.write(out);
        this.CATEGORIES.write(out);
        this.REV_SUMMARY.write(out);
        this.REVIEWS.write(out);

    }
}

问题是：代码在mapper上运行良好，因为mapper中的sysout提供了完美的输出，但在mapper reducer之后，我们永远不会被调用。可写类有什么问题吗？