总结了一下三个方法:hdfs自带 按字节复制 按行复制 (在java io里还有字符复制,暂且不提)
因为hdfs自带的,不知道为什么有些场合不能用,每次能下载的个数还不一定,所以就考虑自己按照java的方式来复制,就出现第2、3种方法。
有时间好好研究一下IO,比如针对特殊文件,文件复制会出现大小不一样的情况。这里
// void downloadFromHdfs(String hdfsSrc , String localDst) // String hdfsDst = "hdfs://54.0.88.53:8020/user/flume/SyslogNetwork/"; // String localDir = "D://flume//"; //下载单个文件 public static boolean downloadFromHdfs(String hdfsSrc, String localDst) { Configuration conf = new Configuration(); Path dst = new Path(hdfsSrc); try { Path Src = new Path(hdfsSrc); String Filename = Src.getName().toString(); String local = localDst + Filename; Path Dst = new Path(local); FileSystem fs = FileSystem.get(URI.create(hdfsSrc), conf); FSDataInputStream in = fs.open(Src); OutputStream output = new FileOutputStream(new File(local)); IOUtils.copyBytes(in, output, 4096, true); System.out.print(" download successed."); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.print(" download failed."); return false; } return true; } //下载目录下所有文件,方法1: IOUtils.copyBytes或者copyToLocal public static boolean downFromHdfsDir(String hdfsSrc, String localDst) throws IOException { Configuration conf = new Configuration(); Path dstpath = new Path(hdfsSrc); int i = 1; FileSystem fs = FileSystem.get(URI.create(hdfsSrc), conf); try { String subPath = ""; FileStatus[] fList = fs.listStatus(dstpath); for (FileStatus f : fList) { if (null != f) { subPath = new StringBuffer() .append(f.getPath().getParent()).append("/") .append(f.getPath().getName()).toString(); if (f.isDir()) { downFromHdfsDir(subPath, localDst); } else { System.out.println("/t/t" + subPath);// hdfs://54.0.88.53:8020/ Path dst = new Path(subPath); i++; FSDataInputStream in = null; OutputStream output = null; try { Path Src = new Path(subPath); String Filename = Src.getName().toString(); String local = localDst + Filename; Path Dst = new Path(local); FileSystem hdfs = FileSystem.get(URI .create(subPath), conf); in = hdfs.open(Src); output = new FileOutputStream(new File(local)); // true-是否关闭数据流,如果是false则在finally里关闭 // IOUtils.copyBytes(in, output, 4096, false); IOUtils.copyBytes(in, output, conf); output.flush(); System.out.print(" download successed."); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.print(" download failed."); } finally { IOUtils.closeStream(in); IOUtils.closeStream(output); } } } } } catch (Exception e) { } finally { System.out.println("the number of files is :" + i); } return true; } //下载目录下所有文件,方法2: 按字节复制 public static boolean downFromHdfsDir2(String hdfsSrc, String localDst) throws IOException { Configuration conf = new Configuration(); Path dstpath = new Path(hdfsSrc); int i = 1; FileSystem fs = FileSystem.get(URI.create(hdfsSrc), conf); try { String subPath = ""; FileStatus[] fList = fs.listStatus(dstpath); for (FileStatus f : fList) { if (null != f) { subPath = new StringBuffer() .append(f.getPath().getParent()).append("/") .append(f.getPath().getName()).toString(); if (f.isDir()) { downFromHdfsDir(subPath, localDst); } else { System.out.println("/t/t" + subPath);// hdfs://54.0.88.53:8020/ Path dst = new Path(subPath); i++; try { Path Src = new Path(subPath); String Filename = Src.getName().toString(); String local = localDst + Filename; Path Dst = new Path(local); FileSystem localFS = FileSystem.getLocal(conf); FileSystem hdfs = FileSystem.get(URI .create(subPath), conf); FSDataInputStream in = hdfs.open(Src); FSDataOutputStream output = localFS.create(Dst); byte[] buf = new byte[1024]; int readbytes = 0; while ((readbytes = in.read(buf)) > 0) { output.write(buf, 0, readbytes); } in.close(); output.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.print(" download failed."); } finally { } } } } } catch (Exception e) { } finally { System.out.println("the number of files is :" + i); } return true; } //下载目录下所有文件,方法2: 按行复制 public static boolean downFromHdfsDir3(String hdfsSrc, String localDst) throws IOException { Configuration conf = new Configuration(); Path dstpath = new Path(hdfsSrc); int i = 1; FileSystem fs = FileSystem.get(URI.create(hdfsSrc), conf); try { String subPath = ""; FileStatus[] fList = fs.listStatus(dstpath); for (FileStatus f : fList) { if (null != f) { subPath = new StringBuffer() .append(f.getPath().getParent()).append("/") .append(f.getPath().getName()).toString(); if (f.isDir()) { downFromHdfsDir(subPath, localDst); } else { System.out.println("/t/t" + subPath);// hdfs://54.0.88.53:8020/ Path dst = new Path(subPath); i++; try { Path Src = new Path(subPath); String Filename = Src.getName().toString(); String local = localDst + Filename; Path Dst = new Path(local); FileSystem localFS = FileSystem.getLocal(conf); FileSystem hdfs = FileSystem.get(URI .create(subPath), conf); FSDataInputStream in = hdfs.open(Src); BufferedReader read = new BufferedReader(new InputStreamReader(in)); BufferedWriter output=new BufferedWriter(new FileWriter(local)); String line = null; while ((line = read.readLine()) != null) { output.append(line); output.newLine(); output.flush(); } in.close(); read.close(); output.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); System.out.print(" download failed."); } finally { } } } } } catch (Exception e) { } finally { System.out.println("the number of files is :" + i); } return true; }
一次读取整个文件
OutputStream:(一次读入整个文件) 字节 private static String readHdfsFile2(FileSystem fs, Path path, String charset) throws IOException { FSDataInputStream hdfsInStream = fs.open(path); ByteArrayOutputStream bos = new ByteArrayOutputStream(); byte[] ioBuffer = new byte[1024]; int readLen = hdfsInStream.read(ioBuffer); while (-1 != readLen) { bos.write(ioBuffer, 0, readLen); readLen = hdfsInStream.read(ioBuffer); } hdfsInStream.close(); return new String(bos.toByteArray(), charset); }
时间: 2024-10-03 23:16:08