at.gv.egovernment.moa.spss.api.Configurator.java Source code

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Here is the source code for at.gv.egovernment.moa.spss.api.Configurator.java

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/*
 * Copyright 2003 Federal Chancellery Austria
 * MOA-SPSS has been developed in a cooperation between BRZ, the Federal
 * Chancellery Austria - ICT staff unit, and Graz University of Technology.
 *
 * Licensed under the EUPL, Version 1.1 or - as soon they will be approved by
 * the European Commission - subsequent versions of the EUPL (the "Licence");
 * You may not use this work except in compliance with the Licence.
 * You may obtain a copy of the Licence at:
 * http://www.osor.eu/eupl/
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the Licence is distributed on an "AS IS" basis,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the Licence for the specific language governing permissions and
 * limitations under the Licence.
 *
 * This product combines work with different licenses. See the "NOTICE" text
 * file for details on the various modules and licenses.
 * The "NOTICE" text file is part of the distribution. Any derivative works
 * that you distribute must include a readable copy of the "NOTICE" text file.
 */

package at.gv.egovernment.moa.spss.api;

import org.apache.commons.discovery.tools.DiscoverClass;

import at.gv.egovernment.moa.spss.MOAException;

/**
 * Configures the SP/SS API.
 * 
 * Also handles dynamic configuration updates. 
 * 
 * @author Patrick Peck
 * @version $Id$
 */
public abstract class Configurator {

    /** The default implementation class. */
    private static final String DEFAULT_IMPLEMENTATION = "at.gv.egovernment.moa.spss.server.init.ConfiguratorImpl";

    /** The single instance of this class. */
    private static Configurator instance = null;

    public static synchronized Configurator getInstance() {
        if (instance == null) {
            try {
                DiscoverClass discover = new DiscoverClass();
                instance = (Configurator) discover.newInstance(Configurator.class, DEFAULT_IMPLEMENTATION);
            } catch (Exception e) {
                // this can not happen since we provide a valid default 
                // implementation
            }
        }
        return instance;
    }

    /**
     * Initialize the SP/SS configuration.
     * 
     * Only a single call to this method will have an effect. Use 
     * <code>update()</code> for reflecting changes in the configuration instead. 
     * 
     * @throws MOAException An error occurred updating the SP/SS configuration.
     */
    public abstract void init() throws MOAException;

    /**
     * Update the SP/SS configuration.
     * 
     * This will only have an effect after the system has been initialized once
     * using <code>init()</code>.
     * 
     * @throws MOAException An error occurred updating the SP/SS configuration.
     */
    public abstract void update() throws MOAException;

}