一步一步跟我学习hadoop(6)----hadoop利用FileSystem API 执行hadoop文件读写操作

    hadoop文件系统较普通的文件系统差异性主要在于其容错性，普通文件系统不能直接查看hadoop的hdfs对应的文件信息。文件存储起来之后，我们是需要可以访问才能够体现它的价值，hadoop提供了FileSystem API来进行hadoop的文件读写。

    本节我是对照hadoop的API中的FileSystem类写的demo，包含了一些主要的方法，更多的需要从相关api中进行查询编写。

package org.apache.hadoop.wyg;import java.io.IOException;import java.net.URI;import org.apache.hadoop.conf.Configuration;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.junit.Test;public class FileSystemAPI {private static final String BASE_URL = "hdfs://192.168.88.128:9000";/** * 追加到文件 * @throws IOException  */@Testpublic void testAppend() throws IOException{Configuration conf= new Configuration();    FileSystem fs = FileSystem.get(URI.create(BASE_URL+"/1.txt"),conf);    fs.append(new Path(BASE_URL+"/user/root/input/2.txt"));    System.out.println();}/**本地文件上传测试 * @throws IOException */@Testpublic void testCopyFromLocalFile() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);fs.copyFromLocalFile(new Path("C:\\Users\\lenovo\\Desktop\\3.txt"), new Path(BASE_URL+"/user/root/input"));}/**从hdfs下载文件到本地 * @throws IOException */@Testpublic void testCopyToLocalFile() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);fs.copyToLocalFile(new Path(BASE_URL+"/user/root/input/3.txt"), new Path("C:\\Users\\lenovo\\Desktop\\4.txt"));}/**测试文件创建 * @throws IOException */@Testpublic void testCreate() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/4.txt");FSDataOutputStream out = fs.create(path,true);out.write("hello hadoop".getBytes());}/**创建空文件 * @throws IOException */@Testpublic void testCreateNewFile() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/5.txt");fs.createNewFile(path);}/**删除文件 * @throws IOException */@Testpublic void testDelete() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/5.txt");fs.delete(path);}/**文件是否存在 * @throws IOException */@Testpublic void testExists() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/5.txt");System.out.println(fs.exists(path));}/**文件状态 * @throws IOException */@Testpublic void testGetFileStatus() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/1.txt");FileStatus status = fs.getFileStatus(path);System.out.println(status.getModificationTime());}/**文件状态，可以获得文件夹信息 * @throws IOException */@Testpublic void testListFile() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input");FileStatus[] status = fs.listStatus(path);for (FileStatus fileStatus : status) {System.out.println(fileStatus.getPath());}}/**创建文件夹 * @throws IOException */@Testpublic void testMkdirs() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/sub");fs.mkdirs(path);}/**移动本地文件到hdfs * @throws IOException */@Testpublic void testMoveFromLocalFile() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/sub");fs.moveFromLocalFile(new Path("C:\\Users\\lenovo\\Desktop\\4.txt"), path);}/**重命名 * @throws IOException */@Testpublic void testRename() throws IOException{Configuration conf = new Configuration();FileSystem fs = FileSystem.get(URI.create(BASE_URL), conf);Path path = new Path("/user/root/input/sub/4.txt");Path dest = new Path("/user/root/input/sub/4_1.txt");fs.rename(path, dest);}}

    源代码下载地址：http://download.csdn.net/detail/wuyinggui10000/8954567