Recipe14.9.Running a Servlet with Jython

Recipe 14.9. Running a Servlet with Jython

Credit: Brian Zhou

Problem

You need to code a servlet using Jython.

Solution

Java (and Jython) are most often deployed server-side, and thus servlets are a typical way of deploying your code. Jython makes servlets very easy to use. Here is a tiny "hello world" example servlet:

import java, javax, sys class hello(javax.servlet.http.HttpServlet):     def doGet(self, request, response):         response.setContentType("text/html")         out = response.getOutputStream( )         print >>out, """<html> <head><title>Hello World</title></head> <body>Hello World from Jython Servlet at %s! </body> </html> """ % (java.util.Date( ),)         out.close( )         return

Discussion

This recipe is no worse than a typical JSP (Java Server Page) (see http://jywiki.sourceforge.net/index.php?JythonServlet for setup instructions). Compare this recipe to the equivalent Java code: with Python, you're finished coding in the same time it takes to set up the framework in Java. Most of your setup work will be strictly related to Tomcat or whichever servlet container you use. The Jython-specific work is limited to copying jython.jar to the WEB-INF/lib subdirectory of your chosen servlet context and editing WEB-INF/web.xml to add <servlet> and <servlet-mapping> tags so that org.python.util.PyServlet serves the *.py <url-pattern>.

The key to this recipe (like most other Jython uses) is that your Jython scripts and modules can import and use Java packages and classes just as if the latter were Python code or extensions. In other words, all of the Java libraries that you could use with Java code are similarly usable with Python (i.e., Jython) code. This example servlet first uses the standard Java servlet response object to set the resulting page's content type (to text/html) and to get the output stream. Afterwards, it can print to the output stream, since the latter is a Python file-like object. To further show off your seamless access to the Java libraries, you can also use the Date class of the java.util package, incidentally demonstrating how it can be printed as a string from Jython.

Recipe14.9.Running a Servlet with Jython