mapreduce中map方法一次读取整个文件

最近有一个项目，需要将爬虫获取的众多网页解析出来，并将内容插入hbase，考虑采用mapreduce来实现。由于一个html文件最大不过几M，所以一个文件将会交给一个map处理，mapreduce中最常见的是按行读取文本文件，而我们需要的是一次读取整个文件内容，然后在map方法中用jsoup解析内容。现将实现一次读取整个文件内容的代码贴出来。

1、定义一个FileInputFormat类

public class WholeFileInputFormat extends FileInputFormat<Text,Text>{

    @Override
    public RecordReader<Text, Text> createRecordReader(InputSplit arg0, TaskAttemptContext arg1) throws IOException,
            InterruptedException {
        // TODO Auto-generated method stub
        RecordReader<Text,Text> recordReader = new WholeFileRecordReader();
        return recordReader;
    }

}

2、自定义RecordReader方法

public class WholeFileRecordReader extends RecordReader<Text,Text>{

    private FileSplit fileSplit;
    private JobContext jobContext;
    private Text currentKey = new Text();
    private Text currentValue = new Text();
    private boolean finishConverting = false;
    @Override
    public void close() throws IOException {
        // TODO Auto-generated method stub

    }

    @Override
    public Text getCurrentKey() throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        return currentKey;
    }

    @Override
    public Text getCurrentValue() throws IOException,
            InterruptedException {
        // TODO Auto-generated method stub
        return currentValue;
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        float progress = 0;
        if(finishConverting){
            progress = 1;
        }
        return progress;
    }

    @Override
    public void initialize(InputSplit arg0, TaskAttemptContext arg1)
            throws IOException, InterruptedException {
        this.fileSplit = (FileSplit) arg0;
        this.jobContext = arg1;
        String filename = fileSplit.getPath().getName();
        this.currentKey = new Text(filename);
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        // TODO Auto-generated method stub
        if(!finishConverting){
            int len = (int)fileSplit.getLength();
// byte[] content = new byte[len];
            Path file = fileSplit.getPath();
            FileSystem fs = file.getFileSystem(jobContext.getConfiguration());
            FSDataInputStream in = fs.open(file);
            BufferedReader br = new BufferedReader(new InputStreamReader(in,"gbk"));
// BufferedReader br = new BufferedReader(new InputStreamReader(in,"utf-8"));
            String line="";
            String total="";
            while((line= br.readLine())!= null){
                total =total+line+"\n";
            }
            br.close();
            in.close();
            fs.close();
            currentValue = new Text(total);
            finishConverting = true;
            return true;
        }
        return false;
    }

}

实现RecordReader接口，最核心的就是处理好迭代多行文本的内容的逻辑，每次迭代通过调用nextKeyValue()方法来判断是否还有可读的文本行，直接设置当前的Key和Value，分别在方法getCurrentKey()和getCurrentValue()中返回对应的值。

更多信息请参考