Projects / jo!


jo! is a pure Java Web server that implements the Servlet API, JSP, and HTTP/1.1. It features advanced thread management, virtual hosts, memory-sensitive file cache, authentication using a role abstraction, automatic compressed transfer of text or HTML files, auto internationalization, auto servlet and JSP reloading, auto reload of WARs, hot deployment of WARs, JSR-45 support, and an easy-to-use Swing console.

Operating Systems

Recent releases

  •  07 Jul 2005 15:13

    Release Notes: This release prominently features JSR-45 support (, which means that you can now debug JSP on the source level. JSR-45 support has been tested with JSwat ( Other improvements are minor bugfixes.

    •  15 Mar 2005 23:17

      Release Notes: This release features some UI enhancements, most importantly clickable filenames in the log panel. This allows JSP developers to simply click on the error message in the log to open the offending Java or JSP file (so far Windows and Mac OS only). It also indicates the exact line number in the Java files as well as the JSP file. Log messages are now color-coded by importance. Under the hood, Java 5 (aka JDK 1.5) compatibility was improved, and the now dispensable DOM implementation was removed.

      •  20 Jan 2005 06:11

        Release Notes: The version added drag-and-drop deployment support, which allows you to simply drag your WAR (Web application archive) onto jo!'s Swing console to deploy it. A Mac OS X disk image was provided. Minor GUI improvements were made and support for system properties expansion was included, allowing you to include a system property in certain configuration parameters such as log file names. This makes it easier to distribute Web applications launched directly from a CD-ROM.

        •  03 Jan 2005 01:19

          Release Notes: The main enhancement in this release is full support for JSP 1.2/Servlet 2.3. Another noteworthy addition is the JSR-45 support. Please note that it is unverified, and feedback is very welcome. The JSP parser now uses standard JDK DOM. XML JSP format and JSP validation are now supported. Support for jikes and Mac OS X was improved.

          •  28 Jun 2004 18:11

            Release Notes: The oal of 1.1 is to provide complete servlet API 2.3 and JSP 1.2 support as well as some other goodies (e.g. run the server as a Windows service). Servlet API 2.3 support should be achieved with this release. JSP 1.2 still has a number of open issues (e.g. XML format support and validation). As this is an alpha release, APIs aren't stable, the documentation is faulty and/or incomplete, etc.


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