Jython and implementing HttpServlet.contextInitialized

Question

I'd like my Jython servlet to implement the HttpServlet.contextInitialized method but I'm not sure how to express this in the web.xml. What I currently have is:

from javax.servlet import ServletContextListener;
from javax.servlet.http import HttpServlet

class JythonServlet1 ( HttpServlet, ServletContextListener ):

        def contextInitialized( self, event ):
            print "contextInitialized"

            context = event.getServletContext()

        def contextDestroyed( self, event ):
            print "contextDestroyed"

            context = event.getServletContext()

        def doGet( self, request, response ):
            print "doGet"

        def doPost( self, request, response ):
            print "doPost"

And my web.xml looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 
    id="WebApp_ID" version="2.5">

  <display-name>JythonTest</display-name>

    <servlet>
        <servlet-name>PyServlet</servlet-name>
        <servlet-class>org.python.util.PyServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>PyServlet</servlet-name>
        <url-pattern>*.py</url-pattern>
    </servlet-mapping>

    <servlet>
        <description></description>
        <display-name>JythonServlet1</display-name>
        <servlet-name>JythonServlet1</servlet-name>
        <servlet-class>JythonServlet1</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

</web-app>

As you can see, in the last <servlet> entry I'd like to initialize the servlet with the context (where I can start a scheduler) but it doesn't seem to work the same as with a Java servlet.

Answer 1

I don't do Jython, but there's no means of contextInitialized or contextDestroyed methods in the HttpServlet API. You're probably looking for ServletContextListener interface which is normally to be implemented as the following Java-based example:

package com.example;

import javax.servlet.ServletContextListener;

public class MyServletContextListener implements ServletContextListener {
    public void contextInitialized(ServletContextEvent event) {
        // ...
    }
    public void contextDestroyed(ServletContextEvent event) {
        // ...
    }
}

...which is to be definied as <listener> in web.xml as follows:

<listener>
    <listener-class>com.example.MyServletContextListener</listener-class>
</listener>

This must give you an idea how to pickup it using Jython.

You can optionally also let your servlet both extend HttpServlet and implement ServletContextListener like follows:

public class MyServlet extends HttpServlet implements ServletContextListener {
    // ...
}

so that you can end up with the code you've posted (don't forget to import the particular interface and define your class as both servlet and listener in web.xml). But this is not always considered a good practice.

That said, you should be placing classes in a package to avoid portability problems. It may work in some environments, but not in other. Sun also discourages using packageless classes in non-prototyping environments. They can normally namely not be imported by other classes which are itself in a package.