对HDFS API基本操作都是通过 org.apache.hadoop.fs.FileSystem类进行的，以下是一些常见的操作：

package HdfsAPI;import java.io.BufferedInputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.net.URI;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.BlockLocation;import org.apache.hadoop.fs.FSDataOutputStream;import org.apache.hadoop.fs.FileStatus;import org.apache.hadoop.fs.FileSystem;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IOUtils;import org.junit.Test;import junit.framework.TestCase;public class HDFSAPI extends TestCase{
            public static String hdfsUrl = "hdfs://master:8020";    //创建文件夹    @Test    public void testHDFSmkdir() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        Path path = new Path("/liguodong/hdfs");        fs.mkdirs(path);    }    //创建文件    @Test    public void testHDFSmkFile() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        Path path = new Path("/liguodong/hdfs/liguodong.txt");        FSDataOutputStream fdos = fs.create(path);         fdos.write("hello hadoop".getBytes());    }    //重命名    @Test    public void testHDFSRenameFile() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        Path path = new Path("/liguodong/hdfs/liguodong.txt");        Path Renamepath = new Path("/liguodong/hdfs/love.txt");        System.out.println(fs.rename(path, Renamepath));    }    //上传一个本地文件    @Test    public void testHDFSPutLocalFile1() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        //因为在windows上面调试，所以选择的是windows的文件夹，        //假设在Linxu，须要Linux文件夹。        Path srcpath = new Path("g:/liguodong.txt");        Path destpath = new Path("/liguodong/hdfs");        fs.copyFromLocalFile(srcpath, destpath);    }    @Test    public void testHDFSPutLocalFile2() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        //因为在windows上面调试，所以选择的是windows的文件夹，        //假设在Linxu，须要Linux文件夹。        String srcpath ="g:/oncemore.txt";        Path destpath = new Path("/liguodong/hdfs/kkk.txt");        InputStream is = new BufferedInputStream(                new FileInputStream(new File(srcpath)));        FSDataOutputStream fdos = fs.create(destpath);        IOUtils.copyBytes(is, fdos, 4094);    }    //查看某个文件夹以下的全部文件    @Test    public void testHDFSListFiles() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        Path path = new Path("/liguodong/hdfs");        FileStatus[] files = fs.listStatus(path);        for (FileStatus file : files) {            System.out.println(file.getPath().toString());        }    }    //查看某个文件的数据块信息    @Test    public void testHDFSGetBlockInfo() throws IOException{        Configuration conf = new Configuration();        FileSystem fs = FileSystem.get(URI.create(hdfsUrl),conf);        Path path = new Path("/liguodong/hdfs/kkk.txt");        FileStatus filestatus = fs.getFileStatus(path);        BlockLocation[] blkLoc = fs.getFileBlockLocations                (filestatus, 0, filestatus.getLen());        for (BlockLocation loc : blkLoc) {            for (int i = 0; i < loc.getHosts().length; i++) {                //获取数据块在哪些主机上                System.out.println(loc.getHosts()[i]);//获取文件块的主机名                //因为这个文件仅仅有一个块。所以输出结果为:slave2、slave1、slave5            }        }    }   }