nz.co.acme.spike.rest.configuration.MongoDb.java Source code

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Here is the source code for nz.co.acme.spike.rest.configuration.MongoDb.java

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/**
 * JerseyMongoDB : A proof of concept ReST / MongoDB service for educational
 * purposes only. Copyright (C) 2014 Michael Chester
 *
 * 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 3 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, see <http://www.gnu.org/licenses/>.
 */
package nz.co.acme.spike.rest.configuration;

import com.mongodb.MongoClient;
import java.net.UnknownHostException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import nz.co.acme.spike.rest.persistence.Access;

/**
 * Set up and tear down the MongoDB connection.
 *
 * Application life cycle host for the MongoDB connection. Sets up the
 * MongoClient when the servlet context is initialised. Closes the client when
 * the context is destroyed.
 *
 * As MongoDB's java driver client is thread safe 'mongoClient' is injected into
 * the static field of the same name in the database 'Access' class. The
 * 'Access' class must only be instantiated following this injection. This
 * ordering is enforced by the servlet context startup order.
 *
 * @author Michael Chester
 */
@WebListener
public class MongoDb implements ServletContextListener {

    private static final Logger logger = Logger.getLogger(MongoDb.class.getName());

    /**
     * Initialise the servlet context with the MongoDB connection.
     *
     * Note that the connection is directly injected into the persistence
     * 'Access' class that class has no way of reaching the servlet context. The
     * connection is added to the servlet context so that it can be picked up
     * when it comes time to destroy the context.
     *
     * @param servletContextEvent
     */
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        try {
            MongoClient mongoClient = new MongoClient();
            servletContext.setAttribute("mongoClient", mongoClient);
            Access.setMongoClient(mongoClient);
            logger.info("Connected to MongoDB using default settings.");
        } catch (UnknownHostException exception) {
            logger.log(Level.SEVERE, "Unable to connect database.", exception);
        }
    }

    /**
     * Close the database connection as a part of servlet context destruction.
     *
     * Retrieves the connection from the servlet context and destroys it. Over
     * zealous containers may warn about possible memory leaks due to threads
     * that the client started not being shut down. Generally this is just the
     * container moaning that it does not manage all of its threads directly. In
     * most cases this warning is not actually valid.
     *
     * @param servletContextEvent
     */
    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        MongoClient mongoClient = (MongoClient) servletContext.getAttribute("mongoClient");
        mongoClient.close();
        logger.info("Closed connection to MongoDB.");
    }

}