重写recordreader以一次读取段落而不是行

q43xntqr  于 2021-06-03  发布在  Hadoop
关注(0)|答案(1)|浏览(306)

我正在重写recordreader类的“next”方法和textinputformat类的“getrecordreader”,以便将整个段落发送到Map器,而不是逐行发送(我使用的是旧的api,我的段落定义是附加的,直到我的文本文件中出现一个空行。)
下面是我的代码:

public class NLinesInputFormat extends TextInputFormat  
{  
   @Override
   public RecordReader<LongWritable, Text> getRecordReader(InputSplit split, JobConf conf, Reporter reporter)throws IOException     {   
        reporter.setStatus(split.toString());  
        return new ParagraphRecordReader(conf, (FileSplit)split);
    }
}

public class ParagraphRecordReader implements RecordReader<LongWritable, Text> 
{
        private LineRecordReader lineRecord;
        private LongWritable lineKey;
        private Text lineValue;
        public ParagraphRecordReader(JobConf conf, FileSplit split) throws IOException {
            lineRecord = new LineRecordReader(conf, split);
            lineKey = lineRecord.createKey();
            lineValue = lineRecord.createValue();
        }

        @Override
        public void close() throws IOException {
            lineRecord.close();
        }

        @Override
        public LongWritable createKey() {
            return new LongWritable();

        }

        @Override
        public Text createValue() {
            return new Text("");

        }

        @Override
        public float getProgress() throws IOException {
            return lineRecord.getPos();

        }

        @Override
        public synchronized boolean next(LongWritable key, Text value) throws IOException {
            boolean appended, gotsomething;
            boolean retval;
            byte space[] = {' '};
            value.clear();
            gotsomething = false;
            do {
                appended = false;
                retval = lineRecord.next(lineKey, lineValue);
                if (retval) {
                    if (lineValue.toString().length() > 0) {
                        byte[] rawline = lineValue.getBytes();
                        int rawlinelen = lineValue.getLength();
                        value.append(rawline, 0, rawlinelen);
                        value.append(space, 0, 1);
                        appended = true;
                    }
                    gotsomething = true;
                }
            } while (appended);

            //System.out.println("ParagraphRecordReader::next() returns "+gotsomething+" after setting value to: ["+value.toString()+"]");
            return gotsomething;
        }

        @Override
        public long getPos() throws IOException {
            return lineRecord.getPos();
        }
    }

问题:
1我没有找到任何具体的指南如何做到这一点,所以可能有什么我做错了请评论任何建议?
2我能够正确地编译这个,但当我运行我的工作,我的Map器是不断运行,我不能找出问题出在哪里?

iyr7buue

iyr7buue1#

你的代码对我来说非常好。我所做的唯一改变是将这些类作为内部类,并使它们成为静态的。
输入文件如下:

This is awesome.
WTF is this.

This is just a test.

Map程序代码如下所示:

@Override
public void map(LongWritable key, Text value, OutputCollector<Text, Text> output, Reporter reporter)
    throws IOException {

    System.out.println(key+" : "+value);
}

结果是:

0 : This is awesome. WTF is this. 
0 : This is just a test.

我相信您不会忘记设置输入格式,但为了以防万一,请按以下方式设置:

conf.setInputFormat(NLinesInputFormat.class);

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