Below is a very simple example for how to print in Tomcat the contents of a file stored in HDFS.<\/p>\n
I am not entirely sure where this would be useful, for the following reasons:<\/p>\n
* Unless you have a list of the output files from a set of map reduce jobs, and can parse the output in a JSP, the raw files may not be relevant
\n* HUE (the Hadoop UI from Cloudera) already has a file browser component<\/p>\n
However, the exercise was very useful in understanding the Hadoop filesystem API, and how it can be used in a web front end.<\/p>\n
Use it as a learning tool.<\/p>\n
\r\n<%@page import=\"java.io.*, java.net.*, java.util.*,org.apache.hadoop.conf.*,org.apache.hadoop.fs.*;\"%>\r\n<%\r\n try {\r\n Configuration conf = new Configuration();\r\n FileSystem fs = FileSystem.get(new URI(\"hdfs:\/\/expressdb1:9000\"), conf);\r\n Path file = new Path(request.getParameter(\"fname\"));\r\n FSDataInputStream getIt = fs.open(file);\r\n BufferedReader d = new BufferedReader(new InputStreamReader(getIt));\r\n String s = \"\";\r\n while ((s = d.readLine()) != null) {\r\n out.println(s + \"
\");\r\n }\r\n d.close();\r\n fs.close();\r\n }\r\n catch (Exception e) {\r\n e.printStackTrace();\r\n }\r\n%>\r\n<\/pre>\nIf you wanted to take this to the next level, you could list every file in HDFS, and construct a hyperlink with the file name. The page would either:<\/p>\n
present a list of hyperlinks to each HDFS file if the fname query string parameter wasn’t present<\/p>\n
-or-<\/p>\n
fetch the file in the fname parameter if the fname query string parameter was present<\/p>\n
What is below does exactly that.<\/p>\n
\r\n<%@page import=\"java.io.*, java.net.*, java.util.*,org.apache.hadoop.conf.*,org.apache.hadoop.fs.*;\"%>\r\n<%\r\n try {\r\n Configuration conf = new Configuration();\r\n FileSystem fs = FileSystem.get(new URI(\"hdfs:\/\/expressdb1:9000\"), conf);\r\n if (request.getParameter(\"fname\") == null) {\r\n RemoteIterator files = fs.listFiles(new Path(\"\/\"),true);\r\n while (files.hasNext()) {\r\n LocatedFileStatus lfs = (LocatedFileStatus)files.next();\r\n out.println(\"\" + lfs.getPath() + \"<\/a>
\");\r\n }\r\n }\r\n else {\r\n Path file = new Path(request.getParameter(\"fname\"));\r\n FSDataInputStream fileIn = fs.open(file);\r\n BufferedReader d = new BufferedReader(new InputStreamReader(fileIn));\r\n String s = \"\";\r\n while ((s = d.readLine()) != null) {\r\n out.println(s + \"
\");\r\n }\r\n d.close();\r\n }\r\n fs.close();\r\n }\r\n catch (Exception e) {\r\n e.printStackTrace();\r\n }\r\n%>\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"Below is a very simple example for how to print in Tomcat the contents of a file stored in HDFS. I am not entirely sure where this would be useful, for the following reasons: * Unless you have a list…<\/p>\n