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主代码：
package api;
import java.io.File;
import java.io.FileOutputStream;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.BlockLocation;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
/**
* 手动拷贝某个特定的数据块（比如某个文件的第二个数据块）
* @author potter
*
*/
public class TestCat {
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
conf.set("fs.defaultFS", "hdfs://potter2:9000");
System.setProperty("HADOOP_USER_NAME", "potter");
FileSystem fs = FileSystem.get(conf);
FSDataInputStream in = fs.open(new Path("/111.zip"));
System.out.println(in+",1111111");
//获取文件信息
FileStatus[] listStatus = fs.listStatus(new Path("/111.zip"));
System.out.println(listStatus.length+",2222222");
//获取文件块的信息
BlockLocation[] blockLocations = fs.getFileBlockLocations(listStatus[0], 0L, listStatus[0].getLen());
System.out.println(blockLocations.length+",3333333");
//获取第二个块的长度
Long lenght = blockLocations[1].getLength();
System.out.println(lenght+",444444444");
//获取第二个块的起始偏移量
Long offset = blockLocations[1].getOffset();
System.out.println(offset+",5555555");
in.seek(offset);
FileOutputStream os = new FileOutputStream(new File("D:/block2"));
//获取第二个块的写入输出流
IOUtils.copyBytes(in, os, lenght, true);
in.close();
os.close();
}
}