操作HDFS集群的JavaAPI

一、准备阶段

首先配置本机的环境变量，配置好HADOOP_HOME；在eclipse中安装好插件，以便在eclipse中操作HDFS集群，将hadoop-eclipse-plugin-2.6.0.jar包放入到eclipse安装文件夹下的dropins文件夹中的plugins下，此后重启eclipse即可在eclipse中操作hdfs集群。
注意： 编写的代码若有操作文件（例如修改、删除等功能）时，需要在本机配置权限的环境变量：HADOOP_USER_NAME=root，这样才会避免在eclipse中出现权限问题。

二、eclipse中的配置

环境变量配置好后，在eclipse中完成配置即可操作hdfs集群：
1）eclipse中的Hadoop控制平台

2）配置好所要连接的namenodeIP地址
此前要修改本机的hosts文件来确定IP地址对应的主机名

3）操作

4）替换工程对应的Hadoop包下的bin文件夹，使其方便操作

5）导入工程必需的jar包

三、JavaAPI代码

/**
 * 1、查看文件
 * 2、创建新文件夹
 * 3、上传文件
 * 4、下载文件
 * 5、删除文件
 * 6、内部移动
 * 7、内部复制
 * 8、重命名
 * 9、创建新的文件
 * 10、写文件
 * 11、读文件内容
 * 
 */
    //操作HDFS之前得先创建配置对象
	Configuration conf = new Configuration(true);
	//创建操作HDFS的对象
	FileSystem fs = FileSystem.get(conf);

功能API代码：

//获取数据的位置
	private static void getFileLocation(FileSystem fs, String string) throws IOException {
		FileStatus fileStatus = fs.getFileStatus(new Path(string));
		long len = fileStatus.getLen();
		BlockLocation[] fileBlockLocations = fs.getFileBlockLocations(fileStatus, 0, len);
		String[] hosts = fileBlockLocations[0].getHosts();
		for (String string2 : hosts) {
			System.out.println(string2);
		}
		
		HdfsBlockLocation blockLocation = (HdfsBlockLocation)fileBlockLocations[0];
		long blockId = blockLocation.getLocatedBlock().getBlock().getBlockId();
		System.out.println(blockId);
	}
//读文件内容
	private static void readFromHDFSFile(FileSystem fs, String string) throws IllegalArgumentException, IOException {
		FSDataInputStream inputStream = fs.open(new Path(string));
		FileStatus fileStatus = fs.getFileStatus(new Path(string));
		long len = fileStatus.getLen();
		
		byte[] b = new byte[(int)len];
		int read = inputStream.read(b);
		while(read != -1){
			System.out.println(new String(b));
			read = inputStream.read(b);
		}
	}
//写文件
private static void writeToHDFSFile(FileSystem fs, String filePath, String content) throws IllegalArgumentException, IOException {
		 FSDataOutputStream outputStream = fs.create(new Path(filePath));
		 outputStream.write(content.getBytes("UTF-8"));
		 outputStream.flush();
		 outputStream.close();
	}
//创建一个新文件
private static void createNewFile(FileSystem fs, String string) throws IllegalArgumentException, IOException {
	fs.createNewFile(new Path(string));
}

//内部移动 内部复制
private static void innerCopyAndMoveFile(FileSystem fs, Configuration conf,String src, String dest) throws IOException {
	Path srcPath = new Path(src);
	Path destPath = new Path(dest);
	//内部拷贝
	FileUtil.copy(srcPath.getFileSystem(conf), srcPath, destPath.getFileSystem(conf), destPath,false, conf);
	//内部移动
	FileUtil.copy(srcPath.getFileSystem(conf), srcPath, destPath.getFileSystem(conf), destPath,true, conf);
}

//重命名
private static void renameFile(FileSystem fs, String src, String dest) throws IOException {
	Path srcPath = new Path(src);
	Path destPath = new Path(dest);
	fs.rename(srcPath, destPath);
}

//下载文件
private static void downLoadFileFromHDFS(FileSystem fs, String src, String dest) throws IOException {
	Path srcPath = new Path(src);
	Path destPath = new Path(dest);
	//copyToLocal
	fs.copyToLocalFile(srcPath, destPath);
	//moveToLocal
	fs.copyToLocalFile(true,srcPath, destPath);
}
//上传文件
private static void uploadFileToHDFS(FileSystem fs, String src, String dest) throws IOException {
	Path srcPath = new Path(src);
	Path destPath = new Path(dest);
	//copyFromLocal
	fs.copyFromLocalFile(srcPath, destPath);
	//moveFromLocal
	fs.copyFromLocalFile(true,srcPath, destPath);
}
//创建文件夹
private static void createDir(FileSystem fs, String string) throws IllegalArgumentException, IOException {
	Path path = new Path(string);
	if(fs.exists(path)){
		fs.delete(path, true);
	}
	fs.mkdirs(path);
}
//查看文件系统的内容
private static List listFileSystem(FileSystem fs, String path) throws FileNotFoundException, IOException {
	Path ppath = new Path(path);	
	FileStatus[] listStatus = fs.listStatus(ppath);		
	for (FileStatus fileStatus : listStatus) {
		System.out.println(fileStatus.getPath());
	}
	return null;
}

//删除文件
private static String del(String path) throws IOException{
			Configuration conf=new Configuration(true);
			FileSystem fs = FileSystem.get(conf);
			Path ppath=new Path(path);
			try {
				fs.delete(ppath);
				fs.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
			System.out.println("删除文件："+ppath);
		}