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- Installation -

Download4J is a JAVA/JSP/Servlets download component.

A [WAR] archive is available to make Download4J installation easier. It needs a servlet engine SERVLETS 2.2+ API compliant or a J2EE1.2+ compliant application server. ZIP and TAR.GZ archives are also available, uncompress and deploy them manually in your servlet engine if you're not familiar with WAR archive.

Any problem ? Read the [FAQ] first. Still a problem ? Post your question to our online JSP Forum.

WAR Installation

Download4J is available as a WAR archive. It's a SERVLETS 2.2 standard archive for Web Applications.
What does it mean ?... It means that WAR installation is as easy as a copy/paste, regardless to the servlet engine vendor.

  1. To install Download4J WAR archive, copy download4j.war under the webapps folder of your servlet engine before running it. That's all :-)
    Note that webapps folder depends on your servlet engine. It could be webapps/, applications/ ... The WAR file will be automatically uncompressed under download4j/ folder.
    Note that application servers (JRun, Websphere, Weblogic, ...) provide a graphical console to install and deploy WAR files.

  2. Run Download4J for the first time :
    Documentation :
    Administration sample :
    Sample 1 :
    Sample 2 :
    Sample 2 :
    Note that at this step, Download4J is running but not configured yet.

  3. Once launched for the first time, stop the servlet engine to setup Download4J (JSP samples and/or configuration file) as you need. Browse the configuration section to learn more about Download4J parameters.

The Download4J WAR archive is downloadable at Download4J HomePage.

  • How to install Download4J ZIP package ?
    Depending on your servlet engine or Application server, you have to create a new web application directory and then uncompress Download4J ZIP or TAR.GZ package into this directory.
  • Is there a JSP sample that work without any customization ?
    Yes, foldersample.jsp is a ready-to-run sample. Matching download source is downloadroot/ folder under WEB-INF/ folder. All is configured and included to make it run without any configuration.
  • I get "404 not found" error when trying to download a file ?
    If filename inludes "%" or ";" or ".." characters then you will get a 404 error because of blacklist filtering. You could reset the blacklist in JSP (Keys.BLACKLIST = null).
  • I get an Exception when running databasesample.jsp ?
    Check that :
    - Your JDBC driver is available in the web application CLASSPATH.
    - Your RDBMS is up.
    - Download4J configuration file matches to the JDBC driver and URL, database account and schema.
  • Could Download4J generate log files with download hits ?
    Yes, enable it in your XML file (e.g. folder.xml) in DOWNLOAD tag such as :
  • How to reload configuration file without restarting the servlet engine ?
    You can't. You have to restart the servlet engine each time you modify the configuration file. We plan to add dynamic reload later.
  • How to integrate UploadBean and Download4J with MySQL ?
    See the following thread for step-by-step instructions.
  • How to implement my own DownloadServlet using Download4J ?
    See API & Design section for a sample source of a DownloadServlet.
  • How to implement my own SQL requests into Download4J ?
    See DownloadMyDB add-on to learn how to override Download4J DownloadSource database implementation. You will see how to pass a custom parameter from JSP to DownloadSource too.
  • How to download files with chinese filename ?
    Checkout and install MultilanguageLink add-on. If your files are in a database, depending on encoding, you might
    have to implement a DownloadSource to translate HTTP request encoding to database encoding.
  • Counters are lost when I restart my servlet engine ?
    Yes, Download4J does not record download hits in file. However you could implement this feature thanks to the DownloadBean notification system.
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