搭建一个web服务下载HDFS的文件

为了能方便快速的获取HDFS中的文件，简单的搭建一个web服务提供下载很方便快速，而且在web服务器端不留临时文件，只做stream中转，效率相当高！
使用的框架是SpringMVC+HDFS API

关键代码 @Controller @RequestMapping("/file") public class FileDownloadController { private static final String BASE_DIR = "/user/app/dump/"; @RequestMapping(value = "/download/{filename}", method = RequestMethod.GET) @ResponseBody public void fileDownload(@PathVariable("filename") String fileName, HttpServletRequest request, HttpServletResponse response) { try { response.setContentType("application/octet-stream; charset=utf-8"); response.addHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName + ".csv", "UTF-8")); String path = BASE_DIR + fileName; HdfsUtils.copyFileAsStream(path, response.getOutputStream()); } catch (Exception e) { e.printStackTrace(); } } }

加载要下载的文件都在 /user/app/dump/这个目录下

下载路径 :port/file/download/xxxfile

HdfsUtils.copyFileAsStream 实现 public class HdfsUtils { private static FileSystem hdfs = null; static { URL.setURLStreamHandlerFactory(new FsUrlStreamHandlerFactory()); Configuration conf=new Configuration(); try { hdfs = FileSystem.get(URI.create("hdfs://xxxxxxx"), conf, "app"); } catch (Exception e) { e.printStackTrace(); } } public static void copyFileAsStream(String fpath, OutputStream out) throws IOException, InterruptedException { org.apache.hadoop.fs.Path path = new org.apache.hadoop.fs.Path(fpath); FSDataInputStream fsInput = hdfs.open(path); IOUtils.copyBytes(fsInput, out, 4096, false); fsInput.close(); out.flush(); } }

是不是非常简单？ HDFS的文件流没落在web服务上，而是直接copy到了浏览器的OutputStream上

更进一步提升性能，压缩

修改 web端的代码, 是zip进行压缩，默认的压缩比例是1：5，大大减少了流在网络上传输量

@Controller @RequestMapping("/file") public class FileDownloadController { private static final String BASE_DIR = "/user/app/dump/"; @RequestMapping(value = "/download/zip/{filename}", method = RequestMethod.GET) @ResponseBody public void hdfsDownload2(@PathVariable("filename") String fileName, HttpServletRequest request, HttpServletResponse response) { try { response.setContentType("application/octet-stream; charset=utf-8"); response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName + ".zip", "UTF-8")); ZipOutputStream zipOut = null; try { zipOut = new ZipOutputStream(new BufferedOutputStream(response.getOutputStream())); zipOut.putNextEntry(new ZipEntry(fileName + ".csv")); } catch (Exception e) { e.printStackTrace(); } String path = BASE_DIR + fileName; HdfsUtils.copyFileAsStream(path, zipOut); zipOut.close(); } catch (Exception e) { e.printStackTrace(); } } } 一些用的主要jar版本 <properties> <spring.version>4.2.5.RELEASE</spring.version> <hadoop.version>2.7.0</hadoop.version> </properties> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-client</artifactId> <version>${hadoop.version}</version> </dependency> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>${hadoop.version}</version> </dependency> </dependencies>