Servlet - save file to disk, but not sure what path to use?

Question

I have a servlet which accepts a file upload, I'd like to store the file in a specific directory on disk. I'm using jetty. The file system looks like this:

/jetty
  /bin
  /contexts
  /stuff
  /webapps
    foo.war   // one web app
    grok.war  // another web app
  start.jar

I start jetty from that start.jar file. In the context of the servlet, I'm not sure how to save the file to my desired destination, the "/stuff" folder:

protected void doPost(HttpServletRequest request, HttpServletResponse response) 
    throws ServletException, IOException 
{
    File downloaded = new File("some/path/here/stuff"); // ?
}

Yeah - I'm not sure what path to use - is there a way I can print the current working directory in java using the File class to figure that out maybe?

Thanks

If you consider it's not specific to Jetty, this question is a duplicate of [Writing to file from within a servlet](http://stackoverflow.com/questions/4482353/writing-to-file-from-within-a-servletdeployertomcat) — rds, Feb 28 '13 at 09:53

score 7 · Accepted Answer · answered Mar 17 '11 at 18:51

This is a pretty poor practice. There is no guarantee that it works on all servletcontainers other than Jetty. Even then, I'm not sure if it works on Jetty. At least, tt would make your webapp unportable to other containers.

When the WAR is expanded (it's servletcontainer specific if and where the WAR will be expanded!), then the ServletContext#getRealPath() can be used to convert a webcontent-relative path to an absolute disk file system path.

When the following line is called in a servlet inside foo.war

String absoluteFooWebPath = getServletContext().getRealPath("/");

and Jetty has expanded the WAR file in the same webapps folder, then this will result in an absolute path to /jetty/webapps/foo. Then, to get from there to /jetty/stuff, you need to navigate two directories up and then from there navigate the stuff directory.

String absoluteStuffPath = getServletContext().getRealPath("../../stuff");

After all, the most reliable way is to specify a servletcontainer-independent fixed path with read/write rights which you document properly in the installation manual of your webapp or to make it configureable by some VM argument / system property.

Agreed it's a horrible practice. – user291701 Mar 17 '11 at 23:48 — user291701, Mar 17 '11 at 23:48

score 0 · Answer 2 · answered Mar 17 '11 at 17:44

You can print the current dir, parent dir using following code:

import java.io.File;
public class FileOperations {
public static void main (String args[]) {
 File dir1 = new File (".");
 File dir2 = new File ("..");
 try {
   System.out.println ("Current dir : " + dir1.getCanonicalPath());
   System.out.println ("Parent  dir : " + dir2.getCanonicalPath());
   }
 catch(Exception e) {
   e.printStackTrace();
   }
 }
}

score 0 · Answer 3 · answered Mar 17 '11 at 18:39

0

The startup.jar should set the jetty.home system property. Access it using System.getProperty("jetty.home").

answered Mar 17 '11 at 18:39

Brent Worden

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score 0 · Answer 4 · answered Mar 09 '12 at 11:46

Though getRealPath is likely to return a valid path when running your war file in Jetty, that is likely to be different when you'll switch to a different app server in future.

It would be better to make it a configurable option in web.xml, using init-param for instance, which would simply contain an absolute path to some pre-existing folder on the server. Putting it in web.xml allows changing it live when using for instance JBoss. You can use getInitParameter on the ServletConfig to get the value.

Servlet - save file to disk, but not sure what path to use?

4 Answers4