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/* ====================================================================
 * 
 * The ObjectStyle Group Software License, version 1.1
 * ObjectStyle Group - http://objectstyle.org/
 * 
 * Copyright (c) 2002-2005, Andrei (Andrus) Adamchik and individual authors
 * of the software. All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * 3. The end-user documentation included with the redistribution, if any,
 *    must include the following acknowlegement:
 *    "This product includes software developed by independent contributors
 *    and hosted on ObjectStyle Group web site (http://objectstyle.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 * 
 * 4. The names "ObjectStyle Group" and "Cayenne" must not be used to endorse
 *    or promote products derived from this software without prior written
 *    permission. For written permission, email
 *    "andrus at objectstyle dot org".
 * 
 * 5. Products derived from this software may not be called "ObjectStyle"
 *    or "Cayenne", nor may "ObjectStyle" or "Cayenne" appear in their
 *    names without prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE OBJECTSTYLE GROUP OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many
 * individuals and hosted on ObjectStyle Group web site.  For more
 * information on the ObjectStyle Group, please see
 * .
 */
package org.objectstyle.cayenne.conf;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpSession;

import org.apache.log4j.Logger;
import org.objectstyle.cayenne.access.DataContext;
import org.objectstyle.cayenne.util.ResourceLocator;
import org.objectstyle.cayenne.util.WebApplicationResourceLocator;

/**
 * Configuration class that uses ServletContext to locate resources. This class is
 * intended for use in J2EE servlet containers. It is compatible with containers following
 * servlet specification version 2.2 and newer (e.g. Tomcat can be used starting from
 * version 3).
 * 
 * ServletConfiguration resolves configuration file locations relative to the web
 * application "WEB-INF" directory, and does not require them to be in the CLASSPATH
 * (though CLASSPATH locations such as "/WEB-INF/classes" and "/WEB-INF/lib/some.jar" are
 * supported as well). By default search for cayenne.xml is done in /WEB-INF/ folder. To
 * specify an arbitrary context path in the web application (e.g. "/WEB-INF/cayenne"), use
 * cayenne.configuration.path context parameters in web.xml.
 * 
 * 
 * @author Andrei Adamchik
 * @author Scott Finnerty
 * @since 1.2
 */
public class ServletUtil {

    private static Logger logObj = Logger.getLogger(ServletUtil.class);

    /**
     * A name of the web application initialization parameter used to specify extra paths
     * where Cayenne XML files might be located. E.g. "/WEB-INF/cayenne".
     */
    public static final String CONFIGURATION_PATH_KEY = "cayenne.configuration.path";

    /**
     * Used by BasicServletConfiguration as a session attribute for DataContext.
     */
    public static final String DATA_CONTEXT_KEY = "cayenne.datacontext";

    /**
     * Creates a new ServletConfiguration and sets is as a Configuration signleton.
     */
    public synchronized static Configuration initializeSharedConfiguration(
            ServletContext context) {

        // check if this web application is already configured

        // don't use static getter, since it will do initialization on demand!!!
        Configuration oldConfig = Configuration.sharedConfiguration;
        if (oldConfig instanceof DefaultConfiguration) {

            ResourceLocator locator = ((DefaultConfiguration) oldConfig)
                    .getResourceLocator();

            if (locator instanceof WebApplicationResourceLocator) {
                if (((WebApplicationResourceLocator) locator).getServletContext() == context) {
                    logObj
                            .info("Configuration is already initialized with this context, reusing.");
                    return oldConfig;
                }
            }
        }

        // create new shared configuration
        DefaultConfiguration conf = new DefaultConfiguration(
                Configuration.DEFAULT_DOMAIN_FILE,
                createLocator(context));
        Configuration.initializeSharedConfiguration(conf);

        return conf;
    }

    /**
     * A helper method to create default ResourceLocator.
     */
    protected static ResourceLocator createLocator(ServletContext context) {
        WebApplicationResourceLocator locator = new WebApplicationResourceLocator();
        locator.setSkipAbsolutePath(true);
        locator.setSkipClasspath(false);
        locator.setSkipCurrentDirectory(true);
        locator.setSkipHomeDirectory(true);

        locator.setServletContext(context);
        String configurationPath = context.getInitParameter(CONFIGURATION_PATH_KEY);
        if (configurationPath != null && configurationPath.trim().length() > 0) {
            locator.addFilesystemPath(configurationPath.trim());
        }

        return locator;
    }

    /**
     * Returns default Cayenne DataContext associated with the HttpSession, creating it on
     * the fly and storing in the session if needed.
     */
    public static DataContext getSessionContext(HttpSession session) {
        synchronized (session) {
            DataContext ctxt = (DataContext) session.getAttribute(DATA_CONTEXT_KEY);

            if (ctxt == null) {
                ctxt = DataContext.createDataContext();
                session.setAttribute(ServletUtil.DATA_CONTEXT_KEY, ctxt);
            }

            return ctxt;
        }
    }
}