public class HdfsClient {
    public static void main(String[] args) throws IOException, InterruptedException, URISyntaxException {
        /**
         * configuration参数对象的机制：
         *      构造时，会先加载jar包中的默认配置 xx-default.xml
         *      再加载用户配置xx-default.xml，覆盖掉默认参数
         *      
         *      构造完成后，还可以conf.set("p", "n")，会再次覆盖用户配置文件中的参数值
         */
        //new Configuration()会从项目的classpath中自动加载core-defult.xml hdfs-defult.xml hdfs-site.xml等文件
        Configuration conf = new Configuration();
        //指定本客户端上传文件到hdfs时需要保存的副本为：2
        conf.set("dfs.replication", "2");
        //指定本客户端上传文件到hdfs时切块的规格大小：64M
        conf.set("dfs.blocksize", "64m");
                
        //构造一个访问指定HDFS系统的客户端对象：参数1:HDFS系统的URI，参数2：客户端指定的参数，参数3：客户身份（用户名）
        FileSystem fs = FileSystem.get(new URI("hdfs://222.18.157.50:9000/"), conf, "root");
        
        
        //上传一个文件到hdfs中
        fs.copyFromLocalFile(new Path("C:\\xxx\\xx\\xx\\xxxx.txt"), new Path("/"));
        
        fs.close();
    }
 }

public class HdfsClient {
    FileSystem fs = null;
    
    @Before
    public void init() throws IOException, InterruptedException, URISyntaxException {

        //new Configuration()会从项目的classpath中自动加载core-defult.xml hdfs-defult.xml hdfs-site.xml等文件
        Configuration conf = new Configuration();

        //指定本客户端上传文件到hdfs时需要保存的副本为：2
        conf.set("dfs.replication", "2");

        //指定本客户端上传文件到hdfs时切块的规格大小：64M
        conf.set("dfs.blocksize", "64m");
                
        //构造一个访问指定HDFS系统的客户端对象：参数1:HDFS系统的URI，参数2：客户端指定的参数，参数3：客户身份（用户名）
        fs = FileSystem.get(new URI("hdfs://222.18.157.50:9000/"), conf, "root");        
    }
    
    /**
     * 从HDFS中下载文件到本地磁盘
     * @throws Exception 
     * @throws IllegalArgumentException 
     */
    @Test
    public void testGet() throws IllegalArgumentException, Exception {
        
        fs.copyToLocalFile(new Path("/xxx.txt"), new Path("F:\\"));
        fs.close();
    }    
}

/**
 * 在HDFS内部移动（修改）文件名称
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testRename() throws Exception {

    fs.rename(new Path("/office激活.txt"), new Path("/install.log"));
        
    fs.close();
}

/**
 * 在HDFS中创建文件夹
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testMkdir() throws IllegalArgumentException, IOException {
    fs.mkdirs(new Path("/client/java"));
    fs.mkdirs(new Path("/client/command"));
    fs.close();
}

/**
 * 在HDFS中删除文件或文件夹
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testRm() throws IllegalArgumentException, IOException {
    fs.delete(new Path("/install.log"), false);
    fs.close();
}

/**
 * 查询HDFS指定目录下的文件信息
 * @throws IOException 
 * @throws IllegalArgumentException 
 * @throws FileNotFoundException 
 */
@Test
public void testLs() throws FileNotFoundException, IllegalArgumentException, IOException {
    // 只查询文件信息，不返回文件夹信息
    RemoteIterator<LocatedFileStatus> iter = fs.listFiles(new Path("/client/java"), true);
    
    while(iter.hasNext()) {
        LocatedFileStatus status = iter.next();
        System.out.println("文件全路径：" + status.getPath());
        System.out.println("块大小：" +  status.getBlockSize());
        System.out.println("文件长度：" + status.getLen());
        System.out.println("副本数量：" + status.getReplication());
        System.out.println("快信息：" + Arrays.toString(status.getBlockLocations()));
        System.out.println("所属用户：" + status.getOwner());
        System.out.println("========华==丽==的==分==割==线========");        
    }
    fs.close();
}

/**
 * 查询HDFS指定目录下的文件和文件夹信息
 * @throws IOException 
 * @throws IllegalArgumentException 
 * @throws FileNotFoundException 
 */
@Test
public void testLs2() throws FileNotFoundException, IllegalArgumentException, IOException {
    FileStatus[] liststatus = fs.listStatus(new Path("/client/"));
    
    for(FileStatus status : liststatus) {
        System.out.println("文件全路径：" + status.getPath());
        System.out.println(status.isDirectory() ? "这是文件夹" : "这是文件");
        System.out.println("块大小：" + status.getBlockSize());
        System.out.println("文件长度：" + status.getLen());
        System.out.println("副本数量：" + status.getReplication());
        System.out.println("========华==丽==的==分==割==线========");
        
    }
    fs.close();
}

/**
 * 读取HDFS中的文件内容
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testReadData() throws IllegalArgumentException, IOException {
    FSDataInputStream in =fs.open(new Path("/doc/HadoopReadMe.txt"));
    
    BufferedReader br = new BufferedReader(new InputStreamReader(in));
    
    String line = null;
    while((line = br.readLine()) != null) {
        System.out.println(line);
    }
    br.close();
    in.close();
    fs.close();
}

/**
 * 读取HDFS中文件指定偏移量范围的内容
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testRandomReadData() throws IllegalArgumentException, IOException {
    FSDataInputStream in = fs.open(new Path("/doc/HadoopReadMe.txt"));
    
    // 指定读取的起始位置
    in.seek(32);
    
    // 指定读取长度：读取64个字节
    byte[] buf =new byte[64];
    in.read(buf);
    
    System.out.println(new String(buf));
    
    in.close();
    fs.close();
}

/**
 * 往HDFS中的文件写数据
 * @throws IOException 
 * @throws IllegalArgumentException 
 */
@Test
public void testWriteData() throws IllegalArgumentException, IOException {
    FSDataOutputStream out = fs.create(new Path("/client/java/testPic.jpg"));
    
    FileInputStream in =new FileInputStream("C:\\xxx\\xx\\Desktop\\xxxx\\xxxx\\xxxx.png");
    
    byte[] buf = new byte[1024];
    int read = 0;
    while((read = in.read(buf)) != -1) {
        out.write(buf, 0, read);
    }
    in.close();
    out.close();
    fs.close();
    
}