读取指定偏移量的数据-蒲公英云

读取指定偏移量的数据

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.Arrays;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocatedFileStatus;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.RemoteIterator;
import org.junit.Before;
import org.junit.Test;
public class HdfsClientDemo {
    FileSystem fs = null;
    @Before
    public void init() throws Exception {
        Configuration conf = new Configuration();
        conf.set("dfs.replication", "2");
        conf.set("dfs.blocksize", "64m");
        fs = FileSystem.get(new URI("hdfs://192.168.228.130:9000/"), conf, "root");
    }
    /**
     * 读取hdfs中文件的指定偏移量范围的内容
     * 从第12个字节开始读，读16个字节
     * 
     * 
     * @throws IOException
     * @throws IllegalArgumentException
     */
    @Test
    public void testRandomReadData() throws IllegalArgumentException, IOException {
        FSDataInputStream in = fs.open(new Path("/xx.dat"));
        // 将读取的起始位置进行指定
        in.seek(12);
        // 读16个字节
        byte[] buf = new byte[16];
        in.read(buf);
        System.out.println(new String(buf));
        in.close();
        fs.close();
    }
}