The name of the context init parameter containing the name of the servlet context attribute under which our resulting Catalog will be stored.

The name of the context init parameter containing a comma-delimited list of class loader resources to be scanned.

The name of the context init parameter containing a comma-delimited list of web applicaton resources to be scanned.

The name of the context init parameter containing the fully qualified class name of the RuleSet implementation for configuring our ConfigParser .

 public  void contextDestroyed(ServletContextEvent event) 
{
    // ------------------------------------------ ServletContextListener Methods
        ServletContext context = event.getServletContext();
        String attr = context.getInitParameter(CONFIG_ATTR);
        if (attr != null) {
            context.removeAttribute(attr);
        }
        CatalogFactory.clear();
}

Remove the configured Catalog from the servlet context attributes for this web application.

 public  void contextInitialized(ServletContextEvent event) 
{
        Log log = LogFactory.getLog(ChainListener.class);
        if (log.isInfoEnabled()) {
            log.info("Initializing chain listener");
        }
        ServletContext context = event.getServletContext();
        // Retrieve context init parameters that we need
        String attr = context.getInitParameter(CONFIG_ATTR);
        String classResources =
            context.getInitParameter(CONFIG_CLASS_RESOURCE);
        String ruleSet = context.getInitParameter(RULE_SET);
        String webResources = context.getInitParameter(CONFIG_WEB_RESOURCE);
        // Retrieve or create the Catalog instance we may be updating
        Catalog catalog = null;
        if (attr != null) {
            catalog = (Catalog) context.getAttribute(attr);
            if (catalog == null) {
                catalog = new CatalogBase();
            }
        }
        // Construct the configuration resource parser we will use
        ConfigParser parser = new ConfigParser();
        if (ruleSet != null) {
            try {
                ClassLoader loader =
                    Thread.currentThread().getContextClassLoader();
                if (loader == null) {
                    loader = this.getClass().getClassLoader();
                }
                Class clazz = loader.loadClass(ruleSet);
                parser.setRuleSet((RuleSet) clazz.newInstance());
            } catch (Exception e) {
                throw new RuntimeException("Exception initalizing RuleSet '"
                                           + ruleSet + "' instance: "
                                           + e.getMessage());
            }
        }
        // Parse the resources specified in our init parameters (if any)
        if (attr == null) {
            parseJarResources(context, parser, log);
            ChainResources.parseClassResources
                (classResources, parser);
            ChainResources.parseWebResources
                (context, webResources, parser);
        } else {
            parseJarResources(catalog, context, parser, log);
            ChainResources.parseClassResources
                (catalog, classResources, parser);
            ChainResources.parseWebResources
                (catalog, context, webResources, parser);
        }
        // Expose the completed catalog (if requested)
        if (attr != null) {
            context.setAttribute(attr, catalog);
        }
}

Scan the required chain configuration resources, assemble the configured chains into a Catalog , and expose it as a servlet context attribute under the specified key.