servletinitializer.java

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//
// This file is part of the OpenNMS(R) Application.
//
// OpenNMS(R) is Copyright (C) 2002-2003 The OpenNMS Group, Inc.  All rights reserved.
// OpenNMS(R) is a derivative work, containing both original code, included code and modified
// code that was published under the GNU General Public License. Copyrights for modified 
// and included code are below.
//
// OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
//
// Modifications:
//
// 2003 Feb 2: Changed Log4J initialization.
//
// Original code base Copyright (C) 1999-2001 Oculan Corp.  All rights reserved.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// For more information contact:
//      OpenNMS Licensing       <[e-mail]>
//      http://www.opennms.org/
//      http://www.opennms.com/
//
// Tab Size = 8
//

package org.opennms.web;

import java.sql.SQLException;
import java.util.Enumeration;
import java.util.Properties;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

import org.apache.log4j.PropertyConfigurator;
import org.opennms.core.resource.Vault;
import org.opennms.core.resource.db.DbConnectionFactory;
import org.opennms.core.utils.ThreadCategory;
import org.opennms.web.log.Log4JLogger;

/**
 * Encapsulates all initialization and configuration needed by the OpenNMS
 * servlets and JSPs.
 * 
 * @author <A HREF="mailto:[e-mail]">Lawrence Karnowski </A>
 * @author <A HREF="http://www.opennms.org/">OpenNMS </A>
 */
public class ServletInitializer extends Object {
    /**
     * A reference to the factory we set in {@link Vault Vault}during
     * {@link #init init}so we can destroy it in {@link #destroy destroy}.
     * 
     * <p>
     * Maybe there's a better way to do this then storing a reference? Should we
     * just add a method to <code>Vault</code>?
     * </p>
     * 
     * <p>
     * This reference also serves as a flag to determine whether or not this
     * class has been initialized yet. If it is null, the class has not yet been
     * initialized.
     * </p>
     */
    protected static DbConnectionFactory factory;

    /**
     * Private, empty constructor so that this class cannot be instantiated
     * outside of itself.
     */
    private ServletInitializer() {
    }

    /**
     * Initialize servlet and JSP configuration on the first invocation of this
     * method. All other invocations are ignored. This method is synchronized to
     * ensure only the first invocation performs the initialization.
     * 
     * <p>
     * Call this method in the <code>init</code> method of your servlet or
     * JSP. It will read the servlet initialization parameters from the
     * <code>ServletConfig</code> and <code>ServletContext</code> and
     * OpenNMS configuration files.
     * </p>
     * 
     * <p>
     * If this method finds the property <code>opennms.db.poolman</code> in
     * the <code>ServletContext</code>, it will create an instance of the
     * classname specified there to use as the <code>DbConnectionManager</code>.
     * </p>
     * 
     * @param context
     *            the <code>ServletContext</code> instance in which your
     *            servlet is running
     */
    public synchronized static void init(ServletContext context) throws ServletException {
        if (context == null) {
            throw new IllegalArgumentException("Cannot take null parameters.");
        }

        // all ThreadCategory instances in the WebUI should use this as their
        // category prefix
        ThreadCategory.setPrefix("OpenNMS.WEB");

        if (factory == null) {
            try {
                String homeDir = context.getInitParameter("opennms.home");

                if (homeDir == null) {
                    throw new ServletException("The opennms.home context parameter must be set.");
                }

                // read the OpenNMS properties
                Properties properties = new Properties(System.getProperties());

                Enumeration initParamNames = context.getInitParameterNames();
                while (initParamNames.hasMoreElements()) {
                    String name = (String) initParamNames.nextElement();
                    properties.put(name, context.getInitParameter(name));
                }

                Vault.setProperties(properties);
                Vault.setHomeDir(homeDir);

                // initialize Log4J for use inside the webapp
                org.apache.log4j.LogManager.resetConfiguration();
                PropertyConfigurator.configure(homeDir + Log4JLogger.propFilename);

                // get the database parameters from the bluebird properties
                String dbUrl = properties.getProperty("opennms.db.url");
                String dbDriver = properties.getProperty("opennms.db.driver");
                String username = properties.getProperty("opennms.db.user");
                String password = properties.getProperty("opennms.db.password");

                // set the database connection pool manager (if one is set in
                // the context)
                String dbMgrClass = context.getInitParameter("opennms.db.poolman");

                if (dbMgrClass != null) {
                    Class clazz = Class.forName(dbMgrClass);
                    factory = (DbConnectionFactory) clazz.newInstance();
                    factory.init(dbUrl, dbDriver, username, password);
                    Vault.setDbConnectionFactory(factory);
                }
            } catch (ClassNotFoundException e) {
                throw new ServletException("Could not find the opennms.db.poolman class", e);
            } catch (InstantiationException e) {
                throw new ServletException("Could not instantiate the opennms.db.poolman class", e);
            } catch (IllegalAccessException e) {
                throw new ServletException("Could not instantiate the opennms.db.poolman class", e);
            } catch (SQLException e) {
                throw new ServletException("Could not initialize a database connection pool", e);
            }
        }
    }

    /**
     * Releases all shared resources on the first invocation of this method. All
     * other invocations are ignored. This method is synchronized to ensure only
     * the first invocation performs the destruction.
     * 
     * <p>
     * Call this method in the <code>destroy</code> method of your servlet or
     * JSP.
     * </p>
     * 
     * @param context
     *            the <code>ServletContext</code> instance in which your
     *            servlet is running
     */
    public synchronized static void destroy(ServletContext context) throws ServletException {
        try {
            if (factory != null) {
                factory.destroy();
                factory = null;
            }
        } catch (Exception e) {
            throw new ServletException("Could not destroy the database connection factory", e);
        }
    }

    /**
     * Return the absolute pathname of where OpenNMS's configuration can be
     * found.
     * 
     * @deprecated Use {@link Vault#getHomeDir Vault.getHomeDir}instead.
     */
    public static String getHomeDir() {
        return (Vault.getHomeDir());
    }

}