This week's book giveaway is in the Servlets forum.
We're giving away four copies of Murach's Java Servlets and JSP and have Joel Murach on-line!
See this thread for details.
The moose likes Servlets and the fly likes Writting to a local file Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login


Win a copy of Murach's Java Servlets and JSP this week in the Servlets forum!
JavaRanch » Java Forums » Java » Servlets
Bookmark "Writting to a local file" Watch "Writting to a local file" New topic
Author

Writting to a local file

Nick Delauney
Ranch Hand

Joined: Sep 28, 2002
Posts: 43
Hello all,
I would like to write to a local file in my web application using servlets.
I'm using tomcat and my servlet is in WEB-INF/servlet. However, if I try to create/write to a file at root of the app by doing "../../logfile.html". I't does not work. Could anyone help me please.
Thanks in advance,


N.D:"Anything worth having, takes time to get"
Ray Stojonic
Ranch Hand

Joined: Aug 08, 2003
Posts: 326
Use an absolute file path based off the results from System.getProperty("user.directory")
Frank Carver
Sheriff

Joined: Jan 07, 1999
Posts: 6920
Any approach you take to this is likely to be server-dependent. It is completely up to the server which directory it uses for the "current directory". Although on some installations getting the user directory might make sense, there are plenty of servlet containers runnning as users which don't have a home directory.
If you need to store files to the file system you have a few basic choices:
  • hard-code the full absolute file name in your code. This is effective only if you are completely sure that the application will only ever be run on one machine, configured in one way. You are almost always better off choosing another alternative.
  • If all you need is to write some sort of file for later use by the same application, the the servlet container is required to provide a "temporary directory" for each application to work in. This may be retrieved using File dir = (File)getServletContext().getAttribute("javax.servlet.context.tempdir");
  • If you have control over the deployment process, it can often make sense to "pass in" the full absolute path of the file as an init parameter in web.xml
  • If you can't control the deployment, you may be better off fetching the full filename from an external source once the application is running using JNDI, a database, HTTP, or whatever suits your application.


  • The bottom line is that you should never depend on the "current directory" or the "user home directory" returning anything sensible in a web application.


    Read about me at frankcarver.me ~ Raspberry Alpha Omega ~ Frank's Punchbarrel Blog
    Michael Cleary
    Ranch Hand

    Joined: Jul 29, 2003
    Posts: 93
    How does one "pass in the full absolute path of the file as an init parameter in web.xml". I need to do this for a small part of a project of mine, and I've never seen any examples of this.
    Thanks,
    Mike


    Mike<br />SCJP 1.4<br />----------------------------<br />mdcleary@earthlink.net<br />----------------------------<br />There are 10 types of people<br />in the world. Those that <br />understand binary, and those<br />that don't.
    Jeroen Wenting
    Ranch Hand

    Joined: Oct 12, 2000
    Posts: 5093

    should return the real path of the WEB-INF directory for your web-app.
    Based on that you should be able to find the directory you need.
    It works on Tomcat, and will likely fail miserably on Novel Extends (SilverStream) as the latter does not use a filesystem to store files.
    Anybody's guess what it will return (and what will happen if you try to write there) if your webapp is contained in a packaged (meaning not expanded at deployment time) warfile.
    Might be interesting to try


    42
    Frank Carver
    Sheriff

    Joined: Jan 07, 1999
    Posts: 6920
    How does one "pass in the full absolute path of the file as an init parameter in web.xml". I need to do this for a small part of a project of mine, and I've never seen any examples of this.
    web.xml:

    in your servlet init method:
    Jeanne Boyarsky
    internet detective
    Marshal

    Joined: May 26, 2003
    Posts: 30068
        
    149

    I didn't see putting the full path in a property file in Frank's list, but that's another way. Then the property file can be changed if you deploy to a different environment and the code can stay the same.


    [Blog] [JavaRanch FAQ] [How To Ask Questions The Smart Way] [Book Promos]
    Blogging on Certs: SCEA Part 1, Part 2 & 3, Core Spring 3, OCAJP, OCPJP beta, TOGAF part 1 and part 2
    Ko Ko Naing
    Ranch Hand

    Joined: Jun 08, 2002
    Posts: 3178
    Originally posted by Jeanne Boyarsky:
    I didn't see putting the full path in a property file in Frank's list, but that's another way.

    What Frank have done is put the param in the web.xml as a context initialization parameters... They are available application-wide to all JSPs and servlets in that web application... We can set such params as much as you need... Hope it helps you to clear the doubt on Frank's implementation...


    Co-author of SCMAD Exam Guide, Author of JMADPlus
    SCJP1.2, CCNA, SCWCD1.4, SCBCD1.3, SCMAD1.0, SCJA1.0, SCJP6.0
     
    It is sorta covered in the JavaRanch Style Guide.
     
    subject: Writting to a local file
     
    Similar Threads
    Having problems with Security
    File Upload....
    problem in running exec() from servlet
    I/O operation in jsp
    Servlet Context and Struts - Action class