StatisticsProviderFactory.java

/*
 *  Licensed to GIScience Research Group, Heidelberg University (GIScience)
 *
 *   	http://www.giscience.uni-hd.de
 *   	http://www.heigit.org
 *
 *  under one or more contributor license agreements. See the NOTICE file
 *  distributed with this work for additional information regarding copyright
 *  ownership. The GIScience licenses this file to you 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 org.heigit.ors.isochrones.statistics;

import org.apache.log4j.Logger;
import org.heigit.ors.exceptions.InternalServerException;
import org.heigit.ors.isochrones.IsochronesErrorCodes;

import java.lang.reflect.InvocationTargetException;
import java.util.HashMap;
import java.util.Map;
import java.util.ServiceLoader;

public class StatisticsProviderFactory {

    private static final Logger LOGGER = Logger.getLogger(StatisticsProviderFactory.class.getName());

    private static final Map<String, StatisticsProviderItem> providers;
    private static final Object lockObj;

    static {
        lockObj = new Object();
        providers = new HashMap<>();
        synchronized (lockObj) {
            ServiceLoader<StatisticsProvider> loader = ServiceLoader.load(StatisticsProvider.class);
            for (StatisticsProvider entry : loader) {
                String name = entry.getName().toLowerCase();
                if (!providers.containsKey(name)) {
                    try {
                        StatisticsProvider provider = entry.getClass().getConstructor().newInstance();
                        StatisticsProviderItem item = new StatisticsProviderItem(provider);
                        providers.put(name, item);
                    } catch (InstantiationException | IllegalAccessException | NoSuchMethodException |
                             InvocationTargetException e) {
                        LOGGER.error(e);
                    }
                }
            }
        }
    }

    private StatisticsProviderFactory() {
    }

    public static StatisticsProvider getProvider(String name, Map<String, Object> parameters) throws Exception {
        if (name == null)
            throw new Exception("Data provider is not defined.");
        StatisticsProvider provider;
        synchronized (lockObj) {
            String pname = name.toLowerCase();
            StatisticsProviderItem item = providers.get(pname);
            if (item == null) {
                Exception ex = new Exception("Unable to find a data provider with name '" + name + "'.");
                LOGGER.error(ex);
                throw new InternalServerException(IsochronesErrorCodes.UNKNOWN, ex.getMessage());
            }
            provider = item.getProvider();
            if (!item.getIsInitialized()) {
                try {
                    provider.init(parameters);
                } catch (Exception ex) {
                    LOGGER.error(ex);
                    throw new InternalServerException(IsochronesErrorCodes.UNKNOWN, "Unable to initialize a data provider with name '" + name + "'.");
                }
                item.setIsInitialized(true);
            }
        }
        return provider;
    }


    public static void releaseProviders() throws Exception {
        synchronized (lockObj) {
            for (Map.Entry<String, StatisticsProviderItem> item : providers.entrySet()) {
                if (item.getValue().getIsInitialized())
                    item.getValue().getProvider().close();
            }
        }
    }
}