org.sakaiproject.component.impl.ContextLoader.java Source code

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/**********************************************************************************
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 * $Id$
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 *
 * Copyright (c) 2005, 2006, 2007, 2008 Sakai Foundation
 *
 * Licensed under the Educational Community 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.opensource.org/licenses/ECL-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.sakaiproject.component.impl;

import java.io.IOException;

import javax.servlet.ServletContext;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.sakaiproject.component.cover.ComponentManager;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.StringUtils;
import org.springframework.web.context.ConfigurableWebApplicationContext;
import org.springframework.web.context.WebApplicationContext;

/**
 * <p>
 * Sakai's extension to Spring's ContextLoader - adds the location of the ComponentManager shared AC, linking the local AC to it as parent, and loading localy hosted components into shared.
 * </p>
 */
public class ContextLoader extends org.springframework.web.context.ContextLoader {
    /** Our logger. */
    private static Log M_log = LogFactory.getLog(ContextLoader.class);

    /** Name of servlet context parameter that can specify the config location for loading into the shared component set. */
    public static final String SHARED_LOCATION_PARAM = "contextSharedLocation";

    /**
     * Initialize the local ApplicationContext, link it to the shared context, and load shared definitions into the shared context.
     * 
     * @param servletContext
     *        current servlet context
     * @return the new WebApplicationContext
     * @throws BeansException
     *         if the context couldn't be initialized
     */
    public WebApplicationContext initWebApplicationContext(ServletContext servletContext) throws BeansException {
        WebApplicationContext rv = super.initWebApplicationContext(servletContext);

        // if we have a parent and any shared bean definitions, load them into the parent
        ConfigurableApplicationContext parent = (ConfigurableApplicationContext) rv.getParent();
        if (parent != null) {
            String sharedConfig = servletContext.getInitParameter(SHARED_LOCATION_PARAM);
            if (sharedConfig != null) {
                String[] locations = StringUtils.tokenizeToStringArray(sharedConfig,
                        ConfigurableWebApplicationContext.CONFIG_LOCATION_DELIMITERS);
                if (locations != null) {
                    XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(
                            (BeanDefinitionRegistry) parent.getBeanFactory());

                    for (int i = 0; i < locations.length; i++) {
                        try {
                            reader.loadBeanDefinitions(rv.getResources(locations[i]));
                        } catch (IOException e) {
                            M_log.warn("exception loading into parent: " + e);
                        }
                    }
                }
            }
        }

        return rv;
    }

    /**
     * Access the shared ApplicationContext
     * 
     * @param servletContext
     *        (not used)
     * @return The shared application context
     */
    protected ApplicationContext loadParentContext(ServletContext servletContext) throws BeansException {
        // get the component manager (we know it's a SpringCompMgr) and from that the shared AC
        ConfigurableApplicationContext sharedAc = ((SpringCompMgr) ComponentManager.getInstance())
                .getApplicationContext();

        return sharedAc;
    }
}