CapsdConfigFactory.java

/*******************************************************************************
 * This file is part of OpenNMS(R).
 *
 * Copyright (C) 2006-2011 The OpenNMS Group, Inc.
 * OpenNMS(R) is Copyright (C) 1999-2011 The OpenNMS Group, Inc.
 *
 * OpenNMS(R) is a registered trademark of The OpenNMS Group, Inc.
 *
 * OpenNMS(R) 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 3 of the License,
 * or (at your option) any later version.
 *
 * OpenNMS(R) 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 OpenNMS(R).  If not, see:
 *      http://www.gnu.org/licenses/
 *
 * For more information contact:
 *     OpenNMS(R) Licensing <license@opennms.org>
 *     http://www.opennms.org/
 *     http://www.opennms.com/
 *******************************************************************************/

package org.opennms.netmgt.config;

import java.io.File;
import java.io.IOException;

import org.exolab.castor.xml.MarshalException;
import org.exolab.castor.xml.ValidationException;
import org.opennms.core.utils.ConfigFileConstants;
import org.opennms.core.utils.ThreadCategory;
import org.springframework.util.Assert;

/**
 * This is the singleton class used to load the configuration for the OpenNMS
 * Capsd service from the capsd-configuration xml file.
 *
 * <strong>Note: </strong>Users of this class should make sure the
 * <em>init()</em> is called before calling any other method to ensure the
 * config is loaded before accessing other convenience methods.
 *
 * @author <a href="mailto:mike@opennms.org">Mike Davidson </a>
 * @author <a href="http://www.opennms.org/">OpenNMS </a>
 * @author <a href="mailto:mike@opennms.org">Mike Davidson </a>
 * @author <a href="http://www.opennms.org/">OpenNMS </a>
 * @version $Id: $
 */
public final class CapsdConfigFactory {
    /**
     * The singleton instance of this factory
     */
    private static CapsdConfig s_singleton = null;
        
    /**
     * This class only has static methods.
     */
    private CapsdConfigFactory() {
        
    }

    /**
     * Load the config from the default config file and create the singleton
     * instance of this factory.
     *
     * @exception java.io.IOException
     *                Thrown if the specified config file cannot be read
     * @exception org.exolab.castor.xml.MarshalException
     *                Thrown if the file does not conform to the schema.
     * @exception org.exolab.castor.xml.ValidationException
     *                Thrown if the contents do not match the required schema.
     * @throws java.io.IOException if any.
     * @throws org.exolab.castor.xml.MarshalException if any.
     * @throws org.exolab.castor.xml.ValidationException if any.
     */
    public static synchronized void init() throws IOException, MarshalException, ValidationException {
        if (isLoaded()) {
            /*
             * init already called - return
             * to reload, reload() will need to be called
             */
            return;
        }

        File cfgFile = ConfigFileConstants.getFile(ConfigFileConstants.CAPSD_CONFIG_FILE_NAME);

        if (log().isDebugEnabled()) {
            log().debug("init: config file path: " + cfgFile.getPath());
        }

        DefaultCapsdConfigManager capsdConfig = new DefaultCapsdConfigManager();
        capsdConfig.update();
        setInstance(capsdConfig);
    }

    private static boolean isLoaded() {
        return s_singleton != null;
    }

    /**
     * Reload the config from the default config file
     *
     * @exception java.io.IOException
     *                Thrown if the specified config file cannot be read/loaded
     * @exception org.exolab.castor.xml.MarshalException
     *                Thrown if the file does not conform to the schema.
     * @exception org.exolab.castor.xml.ValidationException
     *                Thrown if the contents do not match the required schema.
     * @throws java.io.IOException if any.
     * @throws org.exolab.castor.xml.MarshalException if any.
     * @throws org.exolab.castor.xml.ValidationException if any.
     */
    public static synchronized void reload() throws IOException, MarshalException, ValidationException {
        s_singleton = null;

        init();
    }

    /**
     * Return the singleton instance of this factory.
     *
     * @return The current factory instance.
     * @throws java.lang.IllegalStateException
     *             Thrown if the factory has not yet been initialized.
     */
    public static synchronized CapsdConfig getInstance() {
        Assert.state(isLoaded(), "The factory has not been initialized");

        return s_singleton;
    }
    
    /**
     * <p>setInstance</p>
     *
     * @param instance a {@link org.opennms.netmgt.config.CapsdConfig} object.
     */
    public static synchronized void setInstance(CapsdConfig instance) {
        s_singleton = instance;
    }

    private static ThreadCategory log() {
        return ThreadCategory.getInstance(CapsdConfigFactory.class);
    }

}