Jython Interactive Servlet Console

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Q> What is Jython Interactive Servlet Console?

A> It is an interactive Jython Console implemented as a Servlet, hence executable in a web server and accessible using a web browser.

Q> Why do I need it?

A> Well, I often use Jython for debugging/testing my Java application code. The command line version isn't deployable in a web server for web applications, so testing/troubleshooting in a running Web container is not an option with the standard Jython Interactive console.

Q> How is this different from the Jython Servlet?

A> The Jython Servlet can be used to run your Jython code in a WebServer as a servlet. It compiles as a Servlet, so it has access to the HttpServletRequest and such, which is useful for certain applications. However, it is not interactive, it requires you to have access to the server so you can upload the file after modifying it, and it requires that you explicitly print anything you want to see in the output. The Jython Interactive Servlet Console on the other hand does not give you access to HttpServletRequest objects and such, since it does not expose a servlet interface. However, it offers the interactivity and ease of use of a normal Jython console in a web environment.

Q> How do you invoke Jython in this environment?

A> When you access the Jython Interactive Servlet Console, you will see the usage screen as follows:
Use the following syntax to pass any command line arguments to the Jython Interpreter,
or simply press the submit button to launch the interpreter without any arguments. 

Syntax: [options] [-jar jar | -c cmd | file ] [args]

Options and arguments:
-i       : inspect interactively after running script
-S       : don't imply `import site' on initialization
-v       : verbose (trace import statements)
-Dprop=v : Set the property `prop' to value `v'
-c cmd   : program passed in as string (terminates option list)
-W arg   : warning control (arg is action:message:category:module:lineno)
-E codec : Use a different codec the reading from the console.
file     : program read from script file
--help   : print this usage message and exit
--version: print Jython version number and exit
args     : arguments passed to program in sys.argv[1:]
You may enter any arguments in the command window at the bottom and submit, or simply enter submit to start Jython without any command arguments. These arguments are a subset of the arguments accepted by the command line version of the Jython Console. Note: Any file arguments will be relative to the server path, rather than the client path.

Q> How do I install the Jython Interactive Servlet Console?

Installation requires some knowledge of the web.xml deployment descriptors used for servlet deployments and assumes that you are familiar with Jython somewhat. You may use the binary download of jython.jar that contains the Java code for the servlet or build Jython from its CVS sources. Copy the following files relative to the webapps directory.
Next merge the web.xml.fragment from the binary download with your application's web.xml to register the Jython Interactive Servlet Console. Finally, copy your existing jython registry file in the WEB-INF/lib directory and modify the paths according to the server environment. You may also copy the lib directory from your existing jython installation as it is under WEB-INF/lib.

You are now ready to access the Jython Interactive Servlet Console by entering the URL that you associate with it in the web.xml. It should default to http://your.server.com/app-prefix/jython.

Q> How do I build the Jython Interactive Servlet Console?

A> You must download the jython source from its CVS repository and make sure you can build jython before you merge the code for the Jython Interactive Servlet Console. There are only two Java source files required by the Jython Interactive Servlet Console. These files are:
The HTML/JSP files are deployed at the root of the webapp, but are not required during the build.

Q> How do I use the Jython Interactive Servlet Console?

A> Using the Jython Interactive Servlet Console is quite intuitive. See the following screen shot, annotated with relevant help.


Download the binary distribution, which is packaged as a zip file. On Unix/Linux environments, simply use jar to unzip the file.

This download is Not an official distribution. It was built from the CVS source of Jython on November 15, 2003 using JDK 1.3.1. It contains the following files:

If you wish to merge this with the official binary download, you can unjar jython.jar from this distribution and include org.python.util.InteractiveServlet*.class and org.python.util.Text2Html.class in your existing jython.jar. It may work if there are no conflicting changes, but I cannot guarantee that.


You are welcome to use the source code or the binary distribution in any manner you deem fit as long as you retain the copyright in the source code. This code comes with no warranty, whatsoever. It is provided "AS IS", and you must use it at your own risk.

If you are one of the Jython authorities yourself, and would like this to be included in the codebase, please send me an email at vgoenka@hotmail.com.

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