SequenceFile

以 recooed 為單位的有無壓縮的儲存格式	以 Block 為單位的壓縮儲存格式

public class SequenceFileWriteDemo {
    public static void main(String[] args) throws IOException {
        String uri = "/sequence/sequenceFile.txt";
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(URI.create(uri), conf);
        Path path = new Path(uri);
        IntWritable key = new IntWritable();
        Text value = new Text();
        SequenceFile.Writer writer = null;
        try {
            writer = SequenceFile.createWriter(fs, conf, path, key.getClass(), value.getClass());
            for (int i = 0; i < 100; i++) {
                key.set(i+1);
                value.set(String.format("item(%03d) Data", key.get()));
                System.out.printf("len:[%04d] data:%s\n", writer.getLength(), value);
                writer.append(key, value);
            }
        } finally {
            IOUtils.closeStream(writer);
        }
    }
}

public class SequenceFileRead {
    public static void main(String[] args) throws IOException {
        String uri = "/sequence/sequenceFile.txt";
        Configuration conf = new Configuration();
        FileSystem fs = FileSystem.get(URI.create(uri), conf);
        Path path = new Path(uri);
        SequenceFile.Reader reader = null;
        try {
            reader = new SequenceFile.Reader(fs, path, conf);
            Writable key = (Writable) ReflectionUtils.newInstance(reader.getKeyClass(), conf);
            Writable value = (Writable) ReflectionUtils.newInstance(reader.getValueClass(), conf);
            long position = reader.getPosition();
            while (reader.next(key, value)) {
                String syncSeen = reader.syncSeen() ? "Y" : " ";
                System.out.printf("Pos:%04d SyncSeen[%s] data[%03d]=%s\n", position, syncSeen, ((IntWritable)key).get(),    value);
                position = reader.getPosition(); // 下一筆位置
            }
        } finally {
            IOUtils.closeStream(reader);
        }
    }
}