ArchServletContextListener.java

/*******************************************************************************
 * Copyright (c) 2011 The Board of Trustees of the Leland Stanford Junior University
 * as Operator of the SLAC National Accelerator Laboratory.
 * Copyright (c) 2011 Brookhaven National Laboratory.
 * EPICS archiver appliance is distributed subject to a Software License Agreement found
 * in file LICENSE that is included with this distribution.
 *******************************************************************************/
package org.epics.archiverappliance.config;

import java.io.ByteArrayOutputStream;
import java.io.PrintWriter;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

import org.apache.log4j.Logger;

/**
 * This is a ServletContextListener expected to be registered in web.xml that serves as the source of dependency injection.
 * For now, we hardcode the entries, but later these can be picked up from a config file/JNDI if needed.
 * @author mshankar
 *
 */
public class ArchServletContextListener implements ServletContextListener {
	private static final Logger logger = Logger.getLogger(ArchServletContextListener.class);
	private static final Logger configlogger = Logger.getLogger("config." + ArchServletContextListener.class);
	@Override
	public void contextInitialized(ServletContextEvent sce) {
		try {
			String configServiceImplClassName = System.getProperty(ConfigService.ARCHAPPL_CONFIGSERVICE_IMPL);
			if(configServiceImplClassName == null) {
				configServiceImplClassName = System.getenv(ConfigService.ARCHAPPL_CONFIGSERVICE_IMPL);
			}

			ConfigService configService = null;
			if(configServiceImplClassName == null) {
				configlogger.info("Using the default config service implementation");
				configService = new DefaultConfigService();
			} else {
				configlogger.info("Using " + configServiceImplClassName + " as the config service implementation");
				configService = (ConfigService) Class.forName(configServiceImplClassName).newInstance();
			}

			configService.initialize(sce.getServletContext());			
			sce.getServletContext().setAttribute(ConfigService.CONFIG_SERVICE_NAME, configService);
		} catch (Exception e) {
			logger.fatal("Exception initializing config service ", e);
			try { 
				sce.getServletContext().setAttribute(ConfigService.CONFIG_SERVICE_NAME + ".exception", e.getMessage());
				ByteArrayOutputStream bos = new ByteArrayOutputStream();
				PrintWriter stackTraceOut = new PrintWriter(bos, true);
				e.printStackTrace(stackTraceOut);
				bos.flush();
				bos.close();
				sce.getServletContext().setAttribute(ConfigService.CONFIG_SERVICE_NAME + ".stacktrace", bos.toString());
			} catch(Exception ex) { 
				logger.warn("Exception setting reason for failure", ex);
			}
		}
	}

	@Override
	public void contextDestroyed(ServletContextEvent sce) {
		ConfigService configService = (ConfigService) sce.getServletContext().getAttribute(ConfigService.CONFIG_SERVICE_NAME);
		try {
			configService.shutdownNow();
		} catch(Throwable t) {
			logger.warn("Exception shutting down config service using shutdown hook ", t);
		}
	}

}