hadoop-HDFS除了在linux上以shell的方式进行操作外，还可以利用java来操作，接下来我们就来实现吧
【1】新建java工程，引入hadoop的源码包
java操作hadoop1.png
当然，也可以新建lib包，复制hadoop/下的jar
【2】代码操作
方式一：FileSystem与IOUtils
/**
*
* @author mis
* 使用systemfile
*/
public class app2 {
//查看hadoop的根目录下的hello文件
public static final String HDFS_PATH = "hdfs://hadoop:9000/hello";
public static final String DIR_PATH = "/DIR001";
public static final String FILE_PATH = "/DIR001/F1";
private static FsPermission permission;
public static void main(String[] args) throws Exception {
final FileSystem file = FileSystem.get(new URI(HDFS_PATH ), new Configuration());
//创建文件夹
//file.mkdirs(f)
file.mkdirs(new Path(DIR_PATH));
//file.mkdirs(f, permission)
file.mkdirs(new Path("/DIR002"), permission);
//file.mkdirs(fs, dir, permission)
//上传文件
final FSDataOutputStream out = file.create(new Path(FILE_PATH));
final FileInputStream in = new FileInputStream("E:/Demo.py");
IOUtils.copyBytes(in, out, 1024,true);
//下载文件
final FSDataInputStream in = file.open(new Path(FILE_PATH));
IOUtils.copyBytes(in, System.out, 1024,true);
//删除文件（夹）
file.delete(new Path(DIR_PATH), true);
//后边的boolean值是表示 递归与否（如果是删除文件夹就需要用true，问建true或false）
//文件路径是否存在
// boolean falg = file.exists(new Path("/DIR003/file/Demo.py"));
// System.out.println(falg);
//重命名
// file.rename(new Path("/DIR003/Demo1.py"), new Path("/DIR003/Demo.py"));
//是否是文件
// boolean falg1 = file.isFile(new Path("/DIR003/Demo.py"));
// System.out.println(falg1);
//剪切本地文件到hdfs
// file.moveFromLocalFile(new Path("E:/Demo.py"), new Path("/Demo.py"));
//复制本地文件到hdfs
// file.copyFromLocalFile(new Path("E:/Demo.py"), new Path("/Demo.py"));
... ...
}
}
方式二：FileSystem
public class app3 extends TestCase {
public static String hdfsUrl = "hdfs://hadoop:9000";
@Test
// create HDFS folder 创建一个文件夹
public void testHDFSMkdir() throws Exception {
//一般url只认识http协议
//URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory());//保证url也认识hdfs协议，这样就可以解析HDFS_PATH了
//普通操作
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path path = new Path("/test5");
fs.mkdirs(path);
//简化
FileSystem fs = FileSystem.get(new URI(hdfsUrl), new Configuration());
fs.mkdirs(new Path("/dir01"));
}
@Test
// create a file 创建一个文件
public void testCreateFile() throws Exception {
//标准操作
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path path = new Path("/test/a.txt");
FSDataOutputStream out = fs.create(path);
out.write("hello hadoop!".getBytes());
//简单操作
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), new Configuration());
FSDataOutputStream out = fs.create(new Path("/dir01/deom2.txt"));
out.write("hadoop 小试牛刀！".getBytes("utf-8"));
}
@Test
// rename a file 重命名
public void testRenameFile() throws Exception { // rename a file 重命名
//标准操作
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path path = new Path("/test/a.txt");
Path newPath = new Path("/test/bb.txt");
System.out.println(fs.rename(path, newPath));
//简洁操作
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), new Configuration());
System.out.print(fs.rename(new Path("/dir01/deom2.txt"), new Path("/dir01/demo03.txt")));
}
@Test
// 上传文件
public void testUploadLocalFile1() throws Exception { // upload a local file
//标准操作
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path src = new Path("E:/Demo.py");
Path dst = new Path("/test");
fs.copyFromLocalFile(src, dst);
//简洁操作
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), new Configuration());
fs.copyFromLocalFile(new Path("E:/Demo.py"), new Path("/dir01"));
}
@Test
//上传文件
public void testUploadLocalFile2() throws Exception {
//标准书写
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path src = new Path("E:/Demo.py");
Path dst = new Path("/test1");
InputStream in = new BufferedInputStream(new FileInputStream(new File(
"/home/hadoop/hadoop-1.2.1/bin/rcc")));
FSDataOutputStream out = fs.create(new Path("/test/rcc1"));
IOUtils.copyBytes(in, out, 4096);
//简单
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), new Configuration());
final FSDataOutputStream out = fs.create(new Path("/dir01/files"));
final FileInputStream in = new FileInputStream("E:/Demo.py");
IOUtils.copyBytes(in, out, 1024,true);
}
@Test
// 列出文件
public void testListFIles() throws Exception { // list files under folder
//标准书写
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path dst = new Path("/test");
FileStatus[] files = fs.listStatus(dst);
for (FileStatus file : files) {
System.out.println(file.getPath().toString());
}
//简洁书写
FileSystem fs = FileSystem.get(URI.create(hdfsUrl),new Configuration());
FileStatus[] files = fs.listStatus(new Path("/dir01"));
for (FileStatus file : files) {
System.out.println(file.getPath().toString());
}
}
@Test
// 查找文件所在的数据块
public void testGetBlockInfo() throws Exception { // list block info of file
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), conf);
Path dst = new Path("/dir01/Demo.py");
FileStatus fileStatus = fs.getFileStatus(dst);
BlockLocation[] blkloc = fs.getFileBlockLocations(fileStatus, 0,
fileStatus.getLen()); // 查找文件所在数据块
for (BlockLocation loc : blkloc) {
for (int i = 0; i < loc.getHosts().length; i++)
System.out.println(loc.getHosts()[i]);
}
}
@Test
//删除文件、文件夹
public void testRemoveFile () throws Exception {
FileSystem fs = FileSystem.get(URI.create(hdfsUrl), new Configuration());
fs.delete(new Path("/test5"), true);//是否递归删除
}
}