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Configurator Bean library.
There is a newer version: 0.9.104
/*
 * Copyright The Sett Ltd, 2005 to 2014.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.thesett.common.webapp.servlets;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

import org.apache.log4j.Logger;

import com.thesett.common.config.ConfigException;
import com.thesett.common.config.Configurator;

/**
 * ConfigServlet loads and configures config beans at application startup time. Its service method is not implemented as
 * it is not intented to be used as a normal servlet but merely as a convenient place to load config beans. It should
 * normally be set to load on startup and be the first servlet loaded.
 *
 * Here is an example of how to set it up in the web.xml. This assumes that the configuration file has been placed
 * in a file called 'config.xml' which can be found in the root of the classpath of the WAR file.
 *
 * 

 * 
 * <servlet>
 *   <servlet-name>configservlet</servlet-name>
 *   <servlet-class>com.thesett.common.webapp.servlets.ConfigServlet</servlet-class>
 *   <init-param>
 *     <param-name>configResource</param-name>
 *     <param-value>config.xml</param-value>
 *   </init-param>
 *   <load-on-startup>1</load-on-startup>
 * </servlet>
 * 
 *
 * Another way to execute start up code when the web container is started would be to implement a
 * ServletContextListener. There is no way to pass parameters to one in the web.xml so the servlet approach has been
 * used instead.
 *
 * 

 * CRC Card Responsibilities  Collaborations
 * 
 Run the configurator using the specified configuration resource.
 * 
 *
 * @author Rupert Smith
 * @todo   Could make this servlet return some status information about the config beans if its service method is
 *         called.
 */
public class ConfigServlet extends HttpServlet
{
    /** Used for logging. */
    private static final Logger log = Logger.getLogger(ConfigServlet.class);

    /** The name of the config resource parameter. */
    public static final String CONFIG_RESOURCE = "configResource";

    /**
     * Runs the configurator.
     *
     * @throws ServletException If the Log4J config bean fails to configure Log4J.
     */
    public void init() throws ServletException
    {
        log.debug("public void init(): called");

        // Get the name of the configuration resource from the servlet intialization parameters.
        String configResource = getServletConfig().getInitParameter(CONFIG_RESOURCE);

        // Run the configurator.
        Configurator configurator = new Configurator(configResource);

        try
        {
            // Load the config beans.
            configurator.loadConfigBeans();

            // Set up all the loaded config beans.
            configurator.configureAll();
        }
        catch (ConfigException e)
        {
            log.warn("There was a configuration exception whilst loading or running the config beans.", e);
            throw new ServletException(e);
        }
    }

    /** Tells the configurator to remove all its config beans from the JNDI context in which they are registered. */
    public void destroy()
    {
        // Let the super class do its clean up work if it needs to.
        super.destroy();

        // Try to get a reference to the configurator and tell it to remove all its confugred beans from the JNDI
        // context where they are registered.
        Configurator configurator = Configurator.lookupConfigurator();
        configurator.removeAll();
    }
}