如何在map reduce程序中解析PDF文件？

Mehraban 发表于 Dev

Mehraban

我想在hadoop 2.2.0程序中解析PDF文件，我发现了this，遵循了它的意思，直到现在，我拥有这三个类：

PDFWordCount：包含map和reduce函数的主类。（就像本地hadoop wordcount示例一样，但TextInputFormat我没有使用我的PDFInputFormat课程。

PDFRecordReader extends RecordReader<LongWritable, Text>：这是这里的主要工作。尤其是我将initialize功能放在此处以进行更多说明。

public void initialize(InputSplit genericSplit, TaskAttemptContext context)
      throws IOException, InterruptedException {
      System.out.println("initialize");
      System.out.println(genericSplit.toString());
    FileSplit split = (FileSplit) genericSplit;
    System.out.println("filesplit convertion has been done");
    final Path file = split.getPath();
    Configuration conf = context.getConfiguration();
    conf.getInt("mapred.linerecordreader.maxlength", Integer.MAX_VALUE);
    FileSystem fs = file.getFileSystem(conf);
    System.out.println("fs has been opened");
    start = split.getStart();
    end = start + split.getLength();
    System.out.println("going to open split");
    FSDataInputStream filein = fs.open(split.getPath());
    System.out.println("going to load pdf");
    PDDocument pd = PDDocument.load(filein);
    System.out.println("pdf has been loaded");
    PDFTextStripper stripper = new PDFTextStripper();
    in =
    new LineReader(new ByteArrayInputStream(stripper.getText(pd).getBytes(
        "UTF-8")));
    start = 0;
    this.pos = start;
    System.out.println("init has finished");
  }

（您可以看到我system.out.println的进行调试。此方法无法转换genericSplit为FileSplit。我在控制台中看到的最后一件事是：

hdfs://localhost:9000/in:0+9396432

这是 genericSplit.toString()

PDFInputFormat extends FileInputFormat<LongWritable, Text>：仅new PDFRecordReader在createRecordReader方法中创建。

我想知道我的错误是什么？

我需要额外的课程吗？

Padmalcom

读取PDF并不那么困难，您需要扩展FileInputFormat类和RecordReader。由于FileInputClass是二进制文件，因此它们不能拆分PDF文件。

public class PDFInputFormat extends FileInputFormat<Text, Text> {

  @Override
  public RecordReader<Text, Text> createRecordReader(InputSplit split,
    TaskAttemptContext context) throws IOException, InterruptedException {
      return new PDFLineRecordReader();
  }

  // Do not allow to ever split PDF files, even if larger than HDFS block size
  @Override
  protected boolean isSplitable(JobContext context, Path filename) {
    return false;
  }

}

然后，RecordReader自己执行读取（我正在使用PDFBox读取PDF）。

public class PDFLineRecordReader extends RecordReader<Text, Text> {

private Text key = new Text();
private Text value = new Text();
private int currentLine = 0;
private List<String> lines = null;

private PDDocument doc = null;
private PDFTextStripper textStripper = null;

@Override
public void initialize(InputSplit split, TaskAttemptContext context)
        throws IOException, InterruptedException {

    FileSplit fileSplit = (FileSplit) split;
    final Path file = fileSplit.getPath();

    Configuration conf = context.getConfiguration();
    FileSystem fs = file.getFileSystem(conf);
    FSDataInputStream filein = fs.open(fileSplit.getPath());

    if (filein != null) {

        doc = PDDocument.load(filein);

        // Konnte das PDF gelesen werden?
        if (doc != null) {
            textStripper = new PDFTextStripper();
            String text = textStripper.getText(doc);

            lines = Arrays.asList(text.split(System.lineSeparator()));
            currentLine = 0;

        }

    }
}

    // False ends the reading process
@Override
public boolean nextKeyValue() throws IOException, InterruptedException {

    if (key == null) {
        key = new Text();
    }

    if (value == null) {
        value = new Text();
    }

    if (currentLine < lines.size()) {
        String line = lines.get(currentLine);

        key.set(line);

        value.set("");
        currentLine++;

        return true;
    } else {

        // All lines are read? -> end
        key = null;
        value = null;
        return false;
    }
}

@Override
public Text getCurrentKey() throws IOException, InterruptedException {
    return key;
}

@Override
public Text getCurrentValue() throws IOException, InterruptedException {
    return value;
}

@Override
public float getProgress() throws IOException, InterruptedException {
    return (100.0f / lines.size() * currentLine) / 100.0f;
}

@Override
public void close() throws IOException {

    // If done close the doc
    if (doc != null) {
        doc.close();
    }

}