java接口操作Hadoop文件（增删改查）

╰+哭是因爲堅強的太久メ 2023-06-19 14:27 33阅读 0赞

**1 创建文件**

private static String uri = "hdfs://192.168.174.130:8020/"; // hdfs 地址
    	private static String local = "C:/Users/Administrator/Desktop/333.txt"; // 本地路径
    	private static String local1 = "C:/Users/Administrator/Desktop/hdfs";
    	private static String remote = "/user/test1";
    	private static Configuration conf = new Configuration();

// 创建一个目录
    	public static void mkdir() throws Exception {
    		/*
    		 * Configuration 用户加载配置文件
    		 * URI全称为Uniform Resource Identifier，统一资源标识符，作用是标识某一互联网资源。
    		 */
    		  FileSystem fs = FileSystem.get(new URI("hdfs://192.168.131.100:8020"), new
    		  Configuration(), "sheng"); // 创建一个文件夹,这里从HDFS的根目录写起的. 
    		  Boolean flag = fs.mkdirs(new Path("/user/test")); fs.close(); 
    		  System.out.println(flag);
    	}

**2 删除一个文件或者目录**

public static void delete() throws Exception {
    		FileSystem fs = FileSystem.get(new URI("hdfs://192.168.174.130:8020"), new Configuration(), "zx");
    		// 创建一个文件夹,这里从HDFS的根目录写起的.
    		Boolean flag = fs.delete(new Path("/user/test"));
    		fs.close();
    		System.out.println(flag);
    	}

**3 修改文件或者目录**

public static void update() throws Exception {
    		FileSystem fs = FileSystem.get(new URI("hdfs://192.168.174.130:8020"), new Configuration(), "zx");
    		// 创建一个文件夹,这里从HDFS的根目录写起的.
    		Boolean flag = fs.rename(new Path("/user/test1"), new Path("/user/test3"));
    		fs.close();
    		System.out.println(flag);
    	}

**4 上传文件**

public static void go() throws Exception {
    
    		FileSystem fs = FileSystem.get(URI.create(uri), conf);
    		fs.copyFromLocalFile(new Path(local), new Path(remote));
    		System.out.println("copy from: " + local + " to " + remote);
    		fs.close();
    
    	}

**5 下载文件**

public static void get() throws Exception {
    		Path path = new Path(remote);
    		FileSystem fs = FileSystem.get(URI.create(uri), conf);
    		fs.copyToLocalFile(path, new Path(local1));
    		System.out.println("download: from" + remote + " to " + local1);
    		fs.close();
    	}

**6 查看文件内容**

public static void cat() throws Exception {
    		/*
    		 * IOUtils.copyBytes(in, out, 4096, false)
    		 * –in:是FSDataInputStream类的对象，是有关读取文件的类，也就是所谓“输入流”
    		 * –out:是FSDataOutputStream类的对象，是有关文件写入的类，也就是“输出流”
    		 * –4096表示用来拷贝的buffer大小（buffer是缓冲区）–缓冲区大小 –// true -
    		 * 是否关闭数据流，如果是false，就在finally里关掉。IOUtils.closeStream(in);
    		 * 
    		 * 
    		 */
    		String path1 = "/user/test1/333.txt";
    		Path path = new Path(path1);
    		FileSystem fs = FileSystem.get(URI.create(uri), conf);
    		FSDataInputStream fsdis = null;
    		System.out.println("cat: " + path1);
    		try {
    			fsdis = fs.open(path);
    			IOUtils.copyBytes(fsdis, System.out, 4096, false);
    		} finally {
    			IOUtils.closeStream(fsdis);
    			fs.close();
    		}
    	}